Front Page Titles (by Subject) PART III.: GENERAL SYNTHESIS. - The Principles of Psychology
The Online Library of Liberty
A project of Liberty Fund, Inc.
PART III.: GENERAL SYNTHESIS. - Herbert Spencer, The Principles of Psychology 
The Principles of Psychology (London: Longman, Brown, Green and Longmans, 1855).
About Liberty Fund:
Liberty Fund, Inc. is a private, educational foundation established to encourage the study of the ideal of a society of free and responsible individuals.
The text is in the public domain.
Fair use statement:
This material is put online to further the educational goals of Liberty Fund, Inc. Unless otherwise stated in the Copyright Information section above, this material may be used freely for educational and academic purposes. It may not be used in any way for profit.
§ 106. It is a dominant characteristic of Intelligence, viewed in its successive stages of evolution, that its processes, which, as originally performed, were not accompanied with a consciousness of the manner in which they were performed, or of their adaptation to the ends achieved, become eventually both conscious and systematic. Not simply is this seen on comparing the actions popularly distinguished as instinctive and rational; but it is seen on comparing the successive phases of rationality itself. Thus, children reason, but do not know it. Youths know empirically what reason is, and when they are reasoning. Cultivated adults reason intentionally, with a view to certain results. The more advanced of such presently inquire after what manner they reason. And finally, a few reach a state in which they consciously conform their reasonings to those logical principles which analysis discloses. Clearly to exhibit this law of mental progress, and to show the extent of its application, sundry illustrations may be cited.
Classification supplies us with one. All intelligent action presupposes a grouping together of things possessing like properties. To know what is eatable and what not; which creatures to pursue and which to fly; what materials are fit for these purposes and what for those; alike imply the arrangement of objects into classes of such nature, that from certain sensible characteristics of each, certain other characteristics are foreseen. It is manifest that throughout all life, brute and human, more or less of this discrimination is exercised; that it is more exercised by higher creatures than by lower; and that successful action is in part dependent on the extent to which it is pushed. Now it needs but to open a work on Chemistry, Mineralogy, Botany, or Zoology, to see how this classification which the child, the savage, and the peasant, carry on spontaneously, and without thinking what they are doing, is carried on by men of science systematically, knowingly, and with deliberate purpose. It needs but to watch their respective proceedings, to see that the degrees of likeness and unlikeness, which unconsciously guide the ignorant in forming classes and subclasses, are consciously used by the cultured to the same end. And it needs but to contrast the less advanced men of science with the more advanced, to see that this process of making groups, which the first pursue with but little perception of its ultimate use, is pursued by the last with clear ideas of its value as a means of achieving higher objects.
So too is it with nomenclatures. Few will hesitate to admit that in the first stages of language, things were named incidentally—not from a recognition of the value of names as facilitating communication; but under the pressure of particular ideas which it was desired to convey. The poverty of aboriginal tongues, which contain words only for the commonest and most conspicuous objects, serves of itself to show, that systems of verbal signs were, in the beginning, unconsciously extended as far only as necessity impelled. Now, however, nomenclatures are made intentionally. A new star, a new island, a new mineral, a new plant or animal, are severally named by their discoverers as soon as found; and are so named with more or less comprehension of the purpose which names subserve. Moreover it may be remarked that whereas, in the primitive unconscious process of naming, the symbols employed were, as far as might be, descriptive of the things signified; so, in our artificial systems of names—and especially in our chemical one—a descriptive character has been designedly given. Add to which, that whereas there spontaneously grew up in natural nomenclatures, certain habitual ways of combining and inflecting names to indicate composite and modified objects; so, in the nomenclatures of science, systematic modes of forming compound names have been consciously adopted.
Again, a similar progress may be traced in the making of inductions. As is now commonly acknowledged, all general truths are either immediately or mediately inductive—are either themselves derived from aggregations of observed facts, or are deduced from truths that are so derived. The grouping together of the like coexistences and sequences presented by experience, and the formation of a belief that future coexistences and sequences will resemble past ones, is the common type of all initial inferences, whether they be those of the infant or the philosopher. Up to the time of the Greeks, mankind had pursued this process of forming conclusions, unknowingly, as the mass of them pursue it still. Aristotle recognized the fact that certain classes of conclusions were thus formed; and to some extent taught the necessity of so forming them. But it was not until Bacon lived, that the generalization of experiences was erected into a method. Now, however, that all educated men are in a sense Bacon's disciples, we may daily see followed out systematically, and with design, in the investigations of science, those same mental operations which mankind at large have all along unwittingly gone through, in gaining their commonest knowledge of surrounding things. And further, in the valuable “System of Logic” of John Mill, we have now exhibited to us in an organized form, those more complex intellectual procedures which acute thinkers have ever employed, to some extent, in verifying the aboriginal inductive process—procedures which the most advanced inquirers are now beginning to employ with premeditation, and with a recognition of their nature and their purpose.
Another illustration may be drawn from the first part of this work. On reconsidering the chapter treating of the Universal Postulate, it will be seen that the canon of belief there enunciated as the one to be used in testing every premiss, every step in an argument, every conclusion, is one which men have from the beginning used to these ends; that beliefs which are proved by the inconceivableness of their negations to invariably exist, men have, of necessity, always held to be true, though they have not knowingly done this; and that the step remaining to be taken, was simply to apply this test consciously and systematically. It will also be seen that the like may be said of the second canon of belief contained in that chapter; viz. that the certainty of any conclusion is great, in proportion as the assumptions of the Universal Postulate made in reaching it are few. For as was pointed out (§ 8), people in general habitually show but little confidence in results reached by elaborate calculations, or by long chains of reasoning; whilst they habitually show the greatest confidence in results reached by direct perception; and these contrasted classes of results are those which respectively presuppose very many and very few assumptions of the Universal Postulate. In this case therefore, as in the other, the rational criterion is simply the popular criterion analyzed, systematized, and applied with premeditation.
In further exemplification of this law I might enlarge upon the fact, that having found habit to generate facility, we intentionally habituate ourselves to those acts in which facility is desired; upon the fact, that having seen how the mind masters its problems by proceeding from the simple to the complex, we now consciously pursue our scientific inquiries in the same order; upon the fact, that having, in our social operations, spontaneously fallen into division of labour, we now, in any new undertaking, introduce division of labour intentionally. But without multiplying illustrations, it will by this time be sufficiently clear, that, as above said, not only between the so-called instinctive processes and rational ones, is there a difference in respect of the consciousness with which they are performed, but there are analogous differences between the successive gradations of rationality itself.
§ 107. Are we not here then, led to a general doctrine of methods? In each of the cases cited, we see an arranged course of action deliberately pursued with a view to special ends—a method; and on inquiring how one of these methods differs from any conscious intelligent procedure not dignified by the title, we find that it differs only in length and complication. Neglecting this distinction as a merely conventional one—ceasing to regard methods objectively, as written down in books, and regarding them subjectively, as elaborate modes of operation by which the mind reaches certain results—we shall see that they may properly be considered as the highest self-conscious manifestations of the rational faculty. And if, viewed analytically, all methods are simply complex intellectual processes, standing towards conscious reasoning much as conscious reasoning stands towards unconscious reasoning, and as unconscious reasoning stands towards processes lower in the scale—if further, in the several instances above given, methods arose by the systematization and deliberate carrying out of mental operations which were before irregularly and unwittingly pursued—may we not fairly infer that all methods arise after this manner? That they become methods, when the processes they embody have been so frequently repeated as to assume an organized form? And that it is the frequent repetition, which serves alike to give them definiteness, and to attract consciousness to them as processes by which certain ends have been achieved. Is it not indeed obvious, à priori, that no method can be practicable to the intellect save one which harmonizes with its pre-established modes of action? Is it not obvious that the conception of a method by its promulgator implies in the experiences of his own mind, cases in which he has successfully followed such method? Is it not obvious that the advance he makes, consists in observing the processes through which his mind passed on those occasions, and generalizing and arranging them into a system? And is it not then obvious that, both in respect of origin and applicability, no method is possible but such as consists of an orderly and habitual use of the procedures which the intellect spontaneously pursues, but pursues fitfully, incompletely, and unconsciously? The answers can scarcely be doubtful.
By thus carrying consciousness a stage higher, and recognizing the method by which methods are evolved, we may perhaps see our way to further devices in aid of scientific inquiry. As in the case of deductive logic, and classification, and nomenclature, and induction, and the rest, it happened that by becoming conscious of the mode in which the mind wrought in these directions, men were enabled to organize its workings, and consequently to reach results previously unattainable; so, it is possible that by becoming conscious of the method by which methods are formed, we may be assisted in our search after further methods. If in the instances given, the method of forming methods was that of observing the operations by which from time to time the mind spontaneously achieved its ends, and arranging these into a general scheme of action to be constantly followed in analogous cases; then, in whatever directions our modes of inquiry are at present unmethodized, our policy must be to trace the steps by which success is occasionally achieved in these directions; in the hope that by so doing, we may be enabled to frame systems of procedure which shall render future successes more or less sure. That there is scope for this cannot be doubted. On remembering how much, even of the best thinking, is done in an irregular way; how little of the whole chain of thought by which a discovery is made, is included in the bare logical processes; and how unorganized is the part not so included; it will be manifest that there are intellectual operations still remaining to be methodized. And here may fitly be introduced an example, to which, in fact, the foregoing considerations are in a manner introductory.
§ 108. Every generalization is at first an hypothesis. In seeking out the law of any class of phenomena, it is needful to make assumptions respecting it, and then to gather evidence to prove the truth or untruth of the assumptions. The most rigorous adherent of the inductive method, cannot dispense with such assumptions; seeing that without them, he can neither know what facts to look for, nor how to interrogate such facts as he may have. Hypotheses, then, being the indispensable stepping-stones to generalizations—every generalization having to pass through the hypothetic stage—it becomes a question whether there exists any mode of guiding ourselves towards true hypotheses. At present, hypotheses are chosen unsystematically—are suggested by cursory inspections of the phenomena; and the seizing of right ones, seems, in the great majority of cases, a matter of accident. May we not infer however, from the peculiar skill which some men have displayed in the selection of true hypotheses, that there is a special kind of intellectual action by which they are distinguishable. To call the faculty shown by such men, genius, or intuition, is merely to elude the question. If mental phenomena conform to fixed laws, then, an unusual skill in choosing true hypotheses, means nothing else than an unusual tendency to pursue that mental process by which true hypotheses are reached; and this implies that such a process exists.
To identify this process is the problem: to find how, when seeking the law of any group of phenomena, we may make a probable assumption respecting them—how we may guide ourselves to a point of view from which the facts to be generalized can be seen in their fundamental relations. Evidently, as the thing wanted is always an unknown thing, the only possible guidance must be that arising from a foreknowledge of whereabouts it is to be found, or of its general aspect, or of both. If all true generalizations (excluding the merely empirical ones) should possess a peculiarity in common; and this peculiarity should be one not difficult of recognition; the desired guidance may be had. That such a peculiarity exists, will by this time have been inferred; and it now remains to inquire what it is.
§ 109. Most are familiar with the observation, that viewed in one of its chief aspects, scientific progress is constantly towards larger and larger generalizations—towards generalizations, that is, which include the generalizations previously established. Further, the remark has been made, that every true generalization commonly affords an explanation of some other series of facts than the series out of the investigation of which it originated. In both of which propositions we have partial statements of the truth, that each onward step in science is achieved when a group of phenomena to be generalized is brought under the same generalization with some connate group previously considered separate. Let us look at a few cases.
In the Calculus it was thus, when the relationships of extension, linear, superficial, and solid, were found to conform to the same law with those of numbers that are multiplied into each other; and again, when numbers themselves, whether representing spaces, forces, times, objects, or what not, were found to possess certain general properties, capable of being expressed algebraically, which remain the same whatever the magnitudes of the numbers. In Mechanics it was thus, when a formula was discovered which brought the equilibrium of the scales, under the same generalization with the equilibrium of the lever with unequal arms: and again, when the discovery that fluids press equally in all directions, afforded explanations, alike of their uniform tendency towards horizontality, and of their power to support floating bodies. Thus too was it in Astronomy, when the apparently erratic movements of the planets, and the comparatively regular movement of the moon, were explained as both due to similar orbital revolutions; and when the celestial motions, and the falling of rain-drops, were explained as different manifestations of the same force. It was thus in Optics, when the composite nature of light was discovered to be the passive cause of the prismatic spectrum, of the rainbow, and of the colours of objects; in Thermotics, when the expansion of mercury, the rising of smoke, and the boiling of water, were recognized as different manifestations of the same law of expansion by heat; in Acoustics, when the doctrine of undulations was found to apply equally to the phenomena of harmonies, of discords, of pulses, of sympathetic vibrations. Similarly, it was thus in Chemistry, when the burning of coal, the rusting of iron, and the wasting away of starved animals, were generalized as instances of oxidation. It was thus too, when the electro-positive and electro-negative relations of the elements, were brought in elucidation of their chemical affinities. And once more it was thus, when, by the investigations of Œrsted and Ampère, the phenomena of Electricity and Magnetism were reduced to the same category; and the behaviour of the magnetic needle was assimilated to that of a needle subjected to the influence of artificial electric currents.
Now this circumstance, that a true generalization usually brings within one formula groups of phenomena which at first sight seem unallied, is itself a more or less reliable index of the truth of a generalization. For manifestly, to have found for any series of facts, a law which equally applies to some apparently distinct series, implies that we have laid hold of a truth more general than the truths presented by either series regarded separately—more general than the truths which give the special character to either series. If, in the instances above cited, and in hosts of others, we find that the most general fact displayed by any class of phenomena, is also the most general fact displayed by another class, or by several other classes; then, we may conversely infer, on finding a general fact to be true of several cases in each of two separate classes, that there is considerable probability of its being true of all the cases in each class. Or, to exhibit the proposition in another form:—A peculiarity observed to be common to cases that are widely distinct, is more likely to be a fundamental peculiarity, than one which is observed to be common to cases that are nearly related.
Hence, then, is deducible, a method of guiding ourselves towards true hypotheses. For if a characteristic seen equally in instances usually placed in different categories, is more likely to be a general characteristic than one seen equally in instances belonging to the same category; then, it is obviously our policy, when seeking the most general characteristic of any category, not to compare the instances contained in it with each other, but to compare them with instances contained in some allied category. We must seek out all the categories with which alliance is probable; compare some of the phenomena included in each with some of the phenomena under investigation; ascertain by each comparison what there is common to both kinds; and then, if there be any characteristic common to both, inquire whether it is common to all the phenomena we are aiming to generalize: in doing which we may with advantage still act out the same principle, by comparing first the cases that are most strongly contrasted. The adoption of this course secures two advantages. Not only must any peculiarity which may be hit upon, as common to phenomena of separate classes, have a greater probability of being a generic peculiarity, than any one of the many peculiarities possessed in common by phenomena of the same class; but further, we shall be more likely to observe all that there is in common between diverse phenomena placed side by side, than we shall to observe all that there is in common between phenomena so much alike as to be classed together. Fewer hypotheses are possible; all that are possible are likely to be thought of; and of those thought of, each has a much higher chance of being true.
§ 110. And now let us avail ourselves of this method, in searching out a generalization on which to base a synthetic Psychology. We have seen that it is a characteristic of progressive intelligence, eventually to perform consciously, processes which were originally performed unconsciously. We have seen that this truth is illustrated by the erecting into systematic modes of procedure, those higher mental operations which had before been followed irregularly and unconsciously. We have seen that by consciously pursuing this method by which methods are arrived at, there is a probability that further methods may be reached. We have sought by doing this, to find a method of choosing probable hypotheses; and have reached a definite conclusion. Here, leaving these preliminary inquiries, it remains to take advantage of this conclusion in commencing the investigation before us.
CONNEXION OF MIND AND LIFE.
§ 111. The only phenomena to which those of intelligence are allied, are the phenomena of vital activity in its lower forms; and to these their alliance is close. Though we commonly regard mental and bodily life as distinct, it needs only to ascend somewhat above the ordinary point of view, to see that they are but sub-divisions of life in general; and that no line of demarcation can be drawn between them, otherwise than arbitrarily. Doubtless, to those who persist, after the popular fashion, in contemplating only the extreme forms of the two, this assertion will appear as incredible as the assertion that a tree arises by imperceptible changes out of a seed, would appear to one who had seen none of the intermediate stages. But in the absence of prejudice, an examination of the successive links, will produce conviction in the one case as in the other. It is not more certain that from the simple reflex action by which the infant sucks, up to the elaborate reasonings of the adult man, the progress is by daily infinitesimal steps, than it is certain that between the automatic actions of the lowest creatures, and the highest conscious actions of the human race, a series of actions, displayed by the various tribes of the animal kingdom, may be so placed, as to render it impossible to say of any one step in the series—Here intelligence begins. If, from the advanced man of science, pursuing his inquiries with a full understanding of the ratiocinative and inductive processes he employs, we descend to the man of ordinary education, who reasons well and comprehensively, but without knowing how; if, going a grade lower, we analyze the thinkings of the villager, whose highest generalizations are but little wider than those which local events afford data for; if, again, we sink to the inferior human races, who cannot be induced to think, who cannot take in ideas of any complexity, and whose conceptions of number scarcely transcend those of the dog;∗ if we take next the higher quadrumana, hosts of whose actions are quite as rational as those of school-boys, and whose language, however unintelligible to us, is manifestly more or less intelligible to each other; if, from these, we proceed to domesticated animals, whose power of reasoning is conceded even by those under theological bias,† with the qualification that it is special and not general—a qualification which equally holds between the different grades of human reasoning; if, from the most sagacious quadrupeds, we descend to the less and less sagacious ones, noting as we pass how gradual is the transition to those which exhibit no power of modifying their actions to suit special conditions, and which so prove themselves to be guided by what we call instinct; if, from observing the operation of the higher instincts, in which a complicated combination of motions is produced by a complicated combination of stimuli, we go down to the successively lower ones, in which the applied stimuli and the resulting motions are less and less complex; if, presently, we find ourselves merging into what is technically known as reflex action, in which a single motion follows a single stimulus; if, from the creatures in which this implies the irritation of a nerve and the contraction of a muscle, we descend yet lower, to creatures devoid of nervous and muscular systems, and discover that in these the irritability and the contractility are exhibited by the same tissue, which tissue also fulfils the functions of assimilation, secretion, respiration, and reproduction; and if, finally, we perceive that each of the phases of intelligence here instanced, shades off into the adjacent ones by modifications too numerous to specify, too minute to describe, we shall in some measure realize the fact, that no definite separation can be effected between the phenomena of mind and those of vitality in general. Without here, however, urging anything further in support of this position, and without requiring that it shall be admitted, present purposes will be sufficiently served by a recognition of the unquestionable truth, that there is a close relationship between the actions we call mental and the actions we call organic—that these classes of actions are more nearly allied to each other than to any remaining classes.
§ 112. Bodily and mental life being thus divisions of life in general—being related to each other as species of which life in general is the genus—it results from the conclusion reached in the last chapter, that we shall most readily find a true generalization of mental phenomena, by comparing them with the lower vital phenomena, and inquiring what characteristic the two classes have in common. The propriety of this course may be recognized even in the absence of any considerations touching method. Only in some formula which includes all manifestations of intelligence, without exception, can we have a safe and sufficient foundation for a Synthetic Psychology. And saying nothing of the inseparableness of the two orders of vital action, it requires but to consider that the process of making a successful astronomical prediction, differs as widely from that by which the distance of an adjacent body is recognized or the hand moved towards it, as this does from the simple reflex stimulation of a gland—it requires only to consider this, to see that a formula including all manifestations of intelligence, must be one which also includes organic actions. Organic actions, however, and the actions which we class as intelligent, comprehend when taken together all the phenomena of vitality. Hence, then, it follows, that in seeking out a characteristic common to both, we are in fact seeking out the characteristic of vital actions in general—the characteristic by which they are distinguished from non-vital actions. Our point of departure must be an inquiry after that peculiarity displayed alike by all the processes of life.
§ 113. Before proceeding to this inquiry, it may be well to remark, that any conclusion to which it may lead, must be expected to have very little apparent bearing upon our special topic. The more general is any truth, the more vague it is. The greater the range and the more diverse the character of the phenomena, the less apparent relation will a proposition which is true of them all, have to each. Little connection is visible between the axiom—“Things that are equal to the same thing are equal to one another,” and the theorems of Euclid. The law that portions of matter attract each other with a force varying inversely as the square of the distance, does not seem to offer any explanation of the perturbations of Uranus, or the rising of a balloon. Similarly, we may be sure, à priori, that a fact predicable equally of all the infinitely varied actions going on in living bodies, must give little obvious promise of explaining the phenomena classed under the title of Psychology; and especially those highly complex phenomena of human intelligence, with which, in the minds of most, that title is associated.
PROXIMATE DEFINITION OF LIFE.
§ 114. The further we carry our analysis of things, the more manifest does it become, that divisions and classifications are essentially human inventions which have no absolute demarcations in nature corresponding to them, but are simply subjective—are scientific artifices by which we limit and arrange the matter under investigation, and so facilitate our thinking. Hence the circumstance, that when we attempt to frame a definition of anything complex, or make a generalization of facts other than the most simple, we can scarcely ever avoid including more than we intended, or leaving out something that should be taken in. Thus it happens that on seeking a definition of Life which shall be fundamental, we have great difficulty in finding one that is neither more nor less than sufficient—one which takes in all the phenomena, and yet takes in no other phenomena than those commonly considered vital. That this fact may be duly realized, it will be well here to look at a few of the most tenable definitions that have been given; more especially as, in recognizing the respects in which the current ones are defective, we shall see what requirements a more complete one must fulfil.
Schelling, and after him, his plagiarist Coleridge, define Life as—the tendency to individuation. This is a formula which, until studied, conveys little meaning. But it needs only to consider it as interpreted by the facts of development, or by the contrasts between the lower and the higher forms of life, to recognize its value, especially in respect of comprehensiveness. It is objectionable, however, partly on the ground that it refers, not so much to the phenomena constituting Life, as to the formation of those peculiar aggregations of matter which manifest Life; and partly on the ground that it includes under the idea Life, much that we usually exclude from it: as for instance—crystallization.
The definition of Richerand, who says that “Life is a collection of phenomena which succeed each other during a limited time in an organized body,” is liable to the fatal criticism, that it equally applies to the phenomena of decay which go on after death. For these too, constitute “a collection of phenomena which succeed each other during a limited time in an organized body.”
De Blainville's definition—“Life is the two-fold internal movement of composition and decomposition, at once general and continuous”—is in some respects too narrow, and in other respects too wide. On the one hand, while it very well expresses what physiologists distinguish as vegetative life, it wholly excludes those functions of the nervous and muscular systems which form the most conspicuous and distinctive classes of vital phenomena. On the other hand, it describes not only the integrating and disintegrating processes going on in a living body, but it equally well describes those going on in a galvanic battery; which also exhibits a “two-fold internal movement of composition and decomposition, at once general and continuous.”
Elsewhere, I have myself proposed to define Life as— “the co-ordination of actions;”∗ and I still incline towards this definition as one answering to the facts with tolerable precision. It includes all vital processes, alike of the viscera, the limbs, and the brain. It excludes the great mass of inorganic changes, which display little or no co-ordination. By bringing into view co-ordination as the specific characteristic of vitality, it involves the truths, that an arrest of co-ordination is death, and an imperfection of co-ordination is disease. And further, this making co-ordination the essential peculiarity, thoroughly harmonizes with our ordinary ideas of life in all its different gradations: seeing that the organisms which we rank as low, in respect of the life they display, are those which display but little co-ordination of actions; and that from these up to man, the recognized increase in degree of life, corresponds with an increase in the extent and complexity of the co-ordination. But in common with the others, this definition includes too much; for it may be said of the solar system, with its regularly-recurring movements and its self-balancing perturbations, that it, also, exhibits a co-ordination of actions. And however plausibly it may be argued that, in the abstract, the motions of the planets and satellites are as properly comprehended in the idea of life, as the changes going on in a motionless, unsensitive seed; yet, it must be admitted that they are foreign to that idea as commonly received, and as here to be formulated.
It remains to add the definition since suggested by Mr. G. H. Lewes—“Life is a series of definite and successive changes, both of structure and composition, which take place within an individual without destroying its identity.” The last fact which this statement has the merit of bringing into view—the persistence of a living organism as a whole, in spite of the continuous destruction and replacement of its parts—is important. But otherwise it may be argued, that as changes of structure and composition, though probably the causes of muscular and nervous actions, are not the muscular and nervous actions themselves, the definition excludes the more visible movements with which our idea of life is most associated; and further, that in describing vital changes as a series, it scarcely includes the fact, that many of them, as Nutrition, Circulation, Respiration, and Secretion, in their many subdivisions, go on simultaneously.
Thus, however well each of these definitions may express the phenomena of life under one or other of its aspects, no one of them is more than approximately true. It may turn out, that to find one which will bear all tests, is impossible. Meanwhile, it is possible to frame a more adequate formula than any of the foregoing. As we shall presently find, these one and all omit an essential peculiarity of vital changes in general—a peculiarity which, perhaps, more than any other, distinguishes them from non-vital changes. Before specifying this peculiarity, however, it will be well to trace our way, step by step, to as complete an idea of Life as may be reached from our present stand-point: by doing which, we shall both see the necessity for each limitation as it is made, and ultimately be led to feel the need for a further limitation. And here we shall have occasion to follow out in detail, the before-described method of hypotheses; by taking a phenomenon from each of the two grand divisions of vital action, and considering in what they agree.
§ 115. Choosing assimilation, then, for our example of organic life; and the drawing an inference for our example of that life, known as intelligence; it is first to be observed, that they are both processes of change. Without change, food cannot be taken into the blood or transformed into tissue: without change, there can be no getting from premisses to conclusion. And it is this conspicuous manifestation of change, which forms the substratum of our idea of Life in general. It is true that we witness an infinitude of changes to which we attach no notion of vitality—hourly see in inorganic bodies, change of temperature, change of colour, change of aggregation. But it will be admitted that the great majority of the phenomena displayed by inorganic bodies, are statical and not dynamical; that their changes are mostly slow and unobtrusive; that on the one hand, when we see sudden change in inorganic bodies, we are apt to assume living agency, and on the other hand, when we see no change in organic bodies, are apt to assume death. From all which considerations it is manifest, that be the requisite qualifications what they may, a definition of Life must be a definition of some kind of change or changes.
On a further comparison of assimilation and reasoning, with a view of seeing in what respect the process of change displayed in both, differs from non-vital change, we quickly perceive that it differs in being not simple uniform change, but change made up of successive changes. The transformation of food into tissue, involves mastication, deglutition, chymification, chylification, absorption, and those various actions gone through after the lacteal ducts have poured their contents into the blood. The carrying on a chain of reasoning, necessitates a great number of successive states of consciousness, each implying a change of the preceding state. Inorganic changes, however, do not in any considerable degree exhibit this peculiarity. A crystal grows to a certain size and then remains stationary. Exposure to the air may afterwards cause it to effloresce, to deliquesce, to lose its water of crystallization, or, under solar influence, to manifest a new atomic constitution. But successive alterations of state such as these, are not the rule; they are the exceptions. It is not to be denied, indeed, that from meteorological causes, inorganic bodies are daily, sometimes hourly, undergoing modifications of temperature, of bulk, of hygrometric and electric condition. Not only, however, do these modifications lack that conspicuousness and that rapidity of succession which vital ones possess, but vital ones form an additional series. Organic and inorganic bodies are affected in common by meteorological influences, and beyond the changes produced by these, organic bodies exhibit other changes more numerous and more marked. True, therefore, though it is, that organic change cannot be rigorously distinguished from inorganic change by its presenting successive phases—true, though it is, that some inanimate objects, as a watch, display phases of change equally quick and numerous; that there are no objects but what are ever undergoing change of some kind, visible or invisible; and that there are few if any objects which do not, in the lapse of time, undergo a considerable amount of change that is fairly divisible into phases—yet, the change going on in living bodies so greatly exceeds most other change in this respect, that we may consider the varying phases it unceasingly displays, as practically one of its peculiar characteristics. Life, then, as thus roughly differentiated, may be regarded as change presenting successive phases; or otherwise, as a series of changes. And it should be observed, as a fact serving to bring out this characteristic into greater distinctness, that the higher the life the more conspicuous the variations. On comparing inferior with superior organisms, these last will be seen to display more rapid changes, or a much more lengthened series of them, or both.
Contemplating afresh our two typical phenomena, we may see that vital change is further differentiated from non-vital change, by being made up of many simultaneous changes. The process of assimilation does not exhibit simply a series of actions; but it also exhibits many actions going on together. Not only during mastication, is the stomach busy with the food already swallowed, on which it is both pouring out solvent fluids and exercising muscular actions—not only afterwards, while the stomach is still active, are the intestines performing their secretive, contractile, and absorbent functions; but at the same time that one meal is being digested, the nutriment obtained from a previous meal is undergoing that transformation into tissue, which constitutes the final act of assimilation. So also is it, in a certain sense, with mental changes. Though it is true that the states of consciousness which go to make up an argument, occur in series; yet, as each of these successive states is in itself complex—implies the simultaneous excitement of those many faculties by which the perception of any object or relation has been effected; it is obvious that each change in consciousness implies many component changes in the state of the nervous centres. In this respect too, however, it must be admitted that the distinction between animate and inanimate is not precise. No mass of dead matter can have its temperature altered, without at the same time undergoing an alteration in bulk, and sometimes also in hygrometric state. An inorganic body cannot be oxidized, without being at the same time changed in weight, colour, atomic arrangement, temperature, and electric condition. And in some cases, as in that of the sea, the simultaneous as well as the serial changes displayed, are even more numerous than those going on in an animal. Nevertheless, it may still be truly said, that with but few exceptions, a living object is distinguished from a dead one by the peculiarity that the changes at any moment taking place in it are far more numerous. Add to which, that by this peculiarity, as by the previous one, not only is the vital more or less clearly demarcated from the non-vital; but creatures possessing high vitality are demarcated from those possessing low. It needs but to contrast the many organs co-operating in a mammal, with the few in the comparatively structureless polype, to see that the actions which are progressing together in the body of the first, as much exceed in number the actions progressing together in the body of the last, as these do those in a stone. As at present analyzed, then, Life consists of simultaneous and successive changes.
Resorting, as before, to further comparison, we next find that vital changes, both organic and mental, differ from other changes in their heterogeneity. Neither the simultaneous acts nor the serial acts, which together constitute the process of digestion, are at all alike. The states of consciousness comprised in any ratiocination are not similar to each other, either in their composition or in their modes of dependence. Inorganic processes, on the other hand, even when like vital ones in the number of the simultaneous and successive changes they involve, are unlike them in the homogeneity of these changes. For instance, in the case of the sea, just referred to, it is observable that infinite as are the changes at any moment exhibited, they are mostly mechanical changes, to a great degree repetitions of each other: and in this respect, widely differ from the changes at any moment taking place in an organism; which not only belong to the several classes, mechanical, chemical, thermal, electric, but present under each of these classes, innumerable changes differing both in kind and amount. Even where inorganic action most nearly simulates life, as in the working of a steam-engine, we may see that considerable as is the number of simultaneous changes, and rapid as are the successive ones, the regularity with which they shortly recur in the same order and degree, renders them quite unlike those varied changes exhibited by a living creature. Still, it will be found that this peculiarity, like the foregoing ones, does not divide the two classes of changes with precision; inasmuch as there are inanimate things which exhibit considerable heterogeneity of change: for instance, a cloud. The variations of state which this undergoes, both simultaneous and successive, are not only many and quick; but they differ widely from each other both in quality and quantity. At the same instant there may be taking place in a cloud, change of position, change of form, change of size, change of density, change of colour, change of temperature, change of electric state; and these several kinds of change are continuously displaying themselves in different degrees and combinations. Yet notwithstanding this, it needs but to consider that, on the one hand, very few objects in the inorganic world manifest heterogeneity of change in any marked manner, whilst on the other hand, all organic objects manifest it; and further, that in common with preceding characteristics, this characteristic is manifested with increasing conspicuousness as we progress from low to high forms of life, which last exhibit an incomparably greater variety in the kinds and amounts of their changes—it needs but to consider these facts, to perceive that we have here a further leading distinction between organic and inorganic action. At present, then, we may regard Life as made up of heterogeneous changes both simultaneous and successive.
If now we yet again repeat our comparison, for the purpose of finding out in what respect the assimilative and logical processes are distinguished from those inorganic processes which are most like them in the heterogeneity of the simultaneous and successive changes they comprise, we discover that they are distinguished by the combination subsisting among their constituent changes. The acts that go to make up digestion, are mutually dependent: those involved in a train of reasoning possess a close interconnection: and generally, it is to be remarked of vital changes, that each is made possible by all, and all are affected by each. Respiration, circulation, absorption, secretion, in their many sub-divisions, are indissolubly bound up together. Muscular contraction involves chemical change, change of temperature, and change in the excretions. Active thought influences the operations of the stomach, of the heart, of the kidneys. But we miss this peculiarity in inorganic processes. Life-like as may seem the action of a volcano in respect of the heterogeneity of its many simultaneous and successive changes, it is not life-like in respect of the combination subsisting among them. Though the chemical, mechanical, thermal, and electric phenomena exhibited, have a certain interdependence; yet, the emission of stones, mud, lava, flame, ashes, smoke, steam, takes place with no manifest regularity, either in quantity, order, intervals, or mode of conjunction. Even here, however, it cannot be said that inanimate things present no parallels to animate ones. A glacier may be instanced as showing nearly as much combination in its changes as a plant of the lowest organization. It is in constant growth and constant decay; and the rates of its composition and decomposition preserve a tolerably equable ratio. It moves; and its motion is in immediate dependence on its thawing. It emits a torrent of water, which, in common with its motion, undergoes annual variations as plants do: and both also undergo, in summer at least, daily variations. During part of the year, the surface melts and freezes alternately; and on these changes are dependent the variations in progressive movement, and in efflux of water. Thus we have growth, decay, changes of temperature, changes of consistence, changes of velocity, changes of excretion, all going on in mutual dependence: and it may be almost as truly said of a glacier as of an animal, that by ceaseless integration and disintegration it gradually undergoes an entire change of substance without losing its individuality. Exceptional as is this instance, however, it will scarcely be held to weaken that broad distinction between organic and inorganic processes, which the fact of combination among the constituent changes offers. And the reality of this distinction will be yet further realized, on finding that, in common with previous ones, it holds not only between the living and the not-living, but also between things which live little and things which live much—a fact which will be duly recognized on remembering that whilst the changes going on in a plant or a zoophyte, are so imperfectly combined that they can continue after it has been divided into two or more pieces, the combination subsisting amongst the changes going on in a mammal, is so close that no part cut off from the rest can live, and any considerable disturbance of one function causes a cessation of the others. Life then, according to our formula as now modified, is a combination of heterogeneous changes both simultaneous and successive.
On once more looking for a distinction, we shall perceive that the combination of heterogeneous changes which constitutes vitality, differs from the few combinations which otherwise resemble it, in respect of its definiteness. The combined changes going on in a glacier, admit of indefinite variation. Under a conceivable alteration of climate, its thawing and its progression may be entirely arrested for myriads of years, without destroying its capacity for again displaying these phenomena under appropriate conditions. By a geological convulsion, its motion may be arrested without an arrest of its thawing; or by an increase in the inclination of the surface it moves over, its motion may be accelerated without any acceleration of its rate of dissolution. Other things remaining the same, a more rapid deposit of snow may cause an indefinite increase in bulk; or conversely, the accretion may entirely cease, and yet all the other actions continue until the mass finally disappears. Here then, the combination has none of that definiteness, which, in a plant, marks the mutual dependence of assimilation, respiration, and circulation, or the functions of the roots and the functions of the leaves: much less has it that definiteness seen in the mutual dependence of the chief animal functions; no one of which can be varied without varying the rest; no one of which can go on unless the rest go on. It is this definiteness of combination, which distinguishes the changes taking place in a living body from those taking place in a dead one. The process of decomposition exhibits both simultaneous and successive changes, which are to some extent heterogeneous, and in a sense combined; but they are not combined in any definite manner. They will go on differently according as the surrounding medium is air, water, or earth. They will vary in nature with the temperature. If the local conditions are unlike, they will progress differently in different parts of the mass, without any mutual influence. They may end in producing gases, or adipocire, or the dry mouldering substance of which mummies consist. They may occupy a few days, or thousands of years. Thus, neither in their simultaneous nor in their successive changes, do dead bodies display that definiteness of combination which characterizes living ones. It is true that in some inferior creatures, the cycle of successive changes admits of a certain indefiniteness—that it may be suspended for a long period by dessication or freezing; and may afterwards go on as though there had been no breach in its continuity. But the circumstance that it is only a low order of life which permits the cycle of its changes to be thus modified, serves but to suggest that, like the previous characteristics, this characteristic of definiteness in its combined changes, distinguishes high vitality from low vitality, as it distinguishes low vitality from inorganic processes. Hence, our formula as further amended reads thus:—Life is a definite combination of heterogeneous changes, both simultaneous and successive.
Finally it remains only to observe, that we shall still better express the facts, if, instead of saying a definite combination of heterogeneous changes, we say the definite combination of heterogeneous changes. As it at present stands, the definition is defective not only in allowing that there may be other definite combinations of heterogeneous changes, which it should not do; but it has the further defect of directing the attention to the heterogeneous changes as the essential thing, rather than to the definiteness of their combination. Just as it is not so much its chemical elements which constitute an organism, as it is the arrangement of them into special tissues and organs; so it is not so much its heterogeneous changes which constitute life, as it is the definite combination of them. To gain a clear perception of this fact, it needs but to consider what it is that ceases when life ceases. In a dead body there are going on heterogeneous changes, both simultaneous and successive. What then has disappeared? The definite combination has disappeared. Add to which that our common idea of life, turns more upon this member of the definition than upon the others: seeing that however heterogeneous may be the simultaneous and successive changes exhibited by an inorganic object, as a volcano, we much less tend to associate with it the idea of life, than we do with a watch or a steam engine, which, though displaying homogeneous changes, displays them definitely combined. And so dominant an element in our idea of life, is this definite combination, that even when an object is motionless, yet, if its parts be definitely combined, we conclude either that it has had life, or has been made by something having life. In its ultimate shape therefore, we read as our definition of Life—the definite combination of heterogeneous changes, both simultaneous and successive.
§ 116. Such is the conception at which we arrive without changing our stand-point. It is, however, an incomplete conception. This ultimate formula—which it may be observed in passing, is to a considerable extent identical with one above given—“the co-ordination of actions:” seeing that “definite combination” is synonymous with “co-ordination,” and “changes both simultaneous and successive” are comprehended under the term “actions;” but which differs from it in specifying the important fact, that the actions or changes are “heterogeneous”—this ultimate formula, I say, is after all but proximately correct. It is true that it does not fail by including the growth of a crystal; for the successive changes this implies cannot be called heterogeneous. It is true that the action of a galvanic battery is not comprised in it; seeing that here, too, heterogeneity is not exhibited by the successive changes. It is true that by this same qualification the motions of the solar system are excluded: as are also those of a watch and a steam engine. It is true, moreover, that whilst, in virtue of their heterogeneity, the actions going on in a cloud, in a volcano, in a glacier, fulfil the definition; they fall short of it in lacking definiteness of combination. It is further true that this definiteness of combination, distinguishes the changes taking place in an organism during life, from those which commence at death. And beyond all this it is true, that each member of the definition serves not simply to distinguish, more or less markedly, organic actions from inorganic actions, but also serves to distinguish the actions constituting high vitality from those constituting low vitality: seeing that life is high in proportion to the number of successive changes occurring between birth and death; in proportion to the number of simultaneous changes; in proportion to the heterogeneity of the changes; in proportion to the combination subsisting among the changes; and in proportion to the definiteness of their combination. Nevertheless, answering though it does to so many, requirements, this definition is essentially defective. However satisfactorily it may separate from the class of vital actions, the actions which simulate them—however it may thus fulfil the literal requirements of a definition—it does not fulfil the essential one. It does not convey to the mind a complete idea of the thing described. The definite combination of heterogeneous changes, both simultaneous and successive, is a formula which fails to call up an adequate conception. And it fails from omitting the most distinctive peculiarity—the peculiarity of which we have the most familiar experience, and with which our notion of life is, more than with any other, associated. It remains now to supplement the definition by the addition of this peculiarity.
THE CORRESPONDENCE BETWEEN LIFE AND ITS CIRCUMSTANCES.
§ 117. On considering after what manner we habitually distinguish between a live object and a dead one, we shall find that we do so by observing whether a change which we make in the surrounding conditions, or one which Nature makes in them, is or is not followed by some perceptible change in the object. By discovering that certain things shrink when touched, or fly away when approached, or start when a noise is made, the child first roughly discriminates between the living and the not living; and the man when in doubt whether an animal he is looking at is dead or not, stirs it with his stick; or if it be at a distance, shouts, or throws a stone at it. Vegetable and animal life are alike primarily recognized by this process. The tree that puts out leaves when the spring brings a change of temperature; the flower which opens and closes with the rising and setting of the sun; the plant that droops when the soil is dry, and re-erects itself when watered; are considered alive in virtue of these induced changes: in common with the zoophyte which contracts on the passing of a cloud over the sun; the worm that comes out on to the surface when the ground is continuously shaken; and the hedgehog that rolls itself up when attacked.
Not only, however, do we habitually look for some response when an external stimulus is applied to a living organism, but we recognize a certain fitness in the response. Dead as well as living things display changes under certain changes of condition: as a lump of carbonate of soda that effervesces when dropped into sulphuric acid; as a cord that contracts when wetted; as a piece of wood that turns brown when held to the fire. But in these cases, we do not perceive any connection between the changes undergone, and the preservation of the things that undergo them; or, to avoid any teleological implication—the changes have no apparent relation to future external events which are sure or likely to take place. In vital changes, however, such a relation is clearly visible. Light being a necessary of vegetable life, we see in the action of a plant which, when much shaded, grows towards the unshaded side, an appropriateness which we should not see did it grow otherwise. The proceedings of a spider which rushes out when its web is gently shaken, and stays within when the shaking is violent, manifestly conduce better to the obtainment of food, and the avoidance of danger, than were they reversed. And without multiplying familiar illustrations, the fact that we feel surprise when, as in the case of a bird fascinated by a snake, we see actions tending towards self-destruction, at once shows how generally we have observed a harmony between living changes and changes in surrounding circumstances.
Yet further, there remains to notice the hackneyed truth—the truth rendered so common by infinite repetition that we almost forget its significance—that there is invariably, and necessarily, a certain conformity between the vital functions of any organism, and the conditions in which it is placed—between the processes going on inside of it, and the processes going on outside of it. We know that a fish cannot live in air, or a man in water. An oak growing in the ocean, and a seaweed on the top of a mountain, are incredible combinations of ideas. We find that each animal is limited to a certain range of climate; each plant to certain zones of latitude and elevation. Of the marine flora and fauna, each species is found only between such and such depths. Certain blind creatures can flourish only in dark caves; the limpet only where it is alternately covered and uncovered by the tide; the red-snow fungus only in the arctic regions, or among alpine peaks.
Grouping together these two classes of cases—the cases first named, in which a particular change in the circumstances of an organism is followed by a particular change in it, and the case last named, in which the constant actions going on inside of an organism are dependent upon some constant actions going on outside of it,—we see that in both, the changes or processes displayed by a living body, are specially related to the changes or processes in its environment. And in this truth we find the needful supplement to our definition. By the addition of this all-important characteristic, Life is defined as—The definite combination of heterogeneous changes, both simultaneous and successive, in correspondence with external coexistences and sequences. That the full significance of this addition may be seen, it will be necessary to glance at the correspondence under some of its leading aspects.
§ 118. If we study the actions going on in a plant, with the view of ascertaining what they presuppose, we find that, neglecting minor requirements, there needs a surrounding medium containing at least carbonic acid and water, together with a due supply of light and a certain temperature. Within the leaves, carbon is being assimilated and oxygen given off: without them, is the gas from which the carbon is abstracted, and the imponderable agents by whose aid the abstraction is effected. Be the particular character of the process what it may, it is certain that there are external elements prone to undergo special combination under special conditions: it is certain that the plant presents these conditions and so effects these combinations: and thus it is certain that the several cotemporaneous changes which constitute the plant's life, are in correspondence with coexistences in its environment.
If, again, we ask ourselves respecting the lowest animal cell, what are the changes in virtue of which it continues to live; the answer is, that whilst on the one hand its substance is constantly undergoing oxidation, it is on the other hand constantly absorbing new material from the surrounding medium: and that this organic monad may continue to exist, it is needful that on the average the absorption should go on as fast as, or faster than, the oxidation. If further we ask under what circumstances these combined changes are possible; there is the obvious reply, that the medium in which the monad is placed, must contain oxygen and assimilable matter in a certain ratio. The integrating and disintegrating actions, of which, so far as we can ascertain, the life of the cell consists, necessarily presuppose oxygen and food around the cell—the oxygen in such quantity as to produce some disintegration; the food in such quantity as to permit that disintegration to be made good. Or in other words:—the two antagonistic processes taking place internally, must be in correspondence with the two antagonistic elements present externally.
If, again, leaving those lowest animal forms revealed by the microscope, which simply take in through their external surfaces the nutriment and oxygen coming in contact with them, we pass to those somewhat higher and larger forms which possess a digestive cavity—which have their tissue partially specialized into assimilative and respiratory, in adaptation to these two fundamental processes of integration and disintegration—we see in them, a correspondence between certain actions in the digestive sac, and the properties of certain surrounding bodies. That a creature of this order may continue to live, it is, on the one hand, necessary, that there be available substances in the environment capable of transformation into its own tissue; and on the other hand it is necessary that the introduction of these substances into the digestive sac, shall be followed by the secretion of a solvent fluid capable of reducing them into a fit state for absorption.
When, from the process by which food is digested, we turn to the processes by which it is seized, we perceive the same general truth. The stinging and contractile power of a medusa's tentacle, correspond to the sensitiveness and strength of the living creatures serving for prey, amidst which it floats. Unless that external change which ends in bringing a living body in contact with the tentacle, were instantly followed by those internal changes which result in the coiling and drawing up of the tentacle, the medusa would die of inanition: that is, the fundamental processes of integration and disintegration within it, would get out of correspondence with the agencies and processes without it, and the life would cease.
Similarly, it might be shown that when the mass of tissue of which the creature consists, becomes so large that it cannot be efficiently supplied with nutriment by mere absorption through its limiting membranes, or duly aërated by the action of the surrounding fluid upon its surface, there arises a necessity for a circulatory system by which nutriment and oxygen may be distributed throughout the mass—a system whose actions, as subsidiary to the two primary actions, form links in the correspondence between internal and external changes. And the like is obviously true of all those subordinate functions, secretory and excretory, by which oxidation and assimilation are facilitated—functions which exhibit not only various cotemporaneous changes in mediate correspondence with coexistences in the environment; but which further exhibit successive changes, corresponding to those changes of composition, of temperature, of light, of moisture, of pressure, which the environment undergoes.
Ascending from the visceral actions constituting what physiologists term vegetative life, to the muscular and nervous actions of which animal life is made up, we find the correspondence displayed in a manner still more obvious. The successful performance of any act of locomotion, implies the expenditure of certain internal mechanical forces, adapted in amount and direction to overcome certain external ones. The recognition of an object, implies a harmony between the changes constituting perception, and the particular colours, size, and form, coexisting in the environment. Escape from enemies, presupposes motions within the organism, related in kind and rapidity to motions without it. Destruction of prey, requires a particular combination of subjective changes fitted in amount and succession to counterbalance a group of objective ones. And so with that infinity of adapted actions exemplified at length in works on animal instincts.
In the highest order of vital processes, the same fact is equally manifest. The empirical generalization that guides the farmer in his rotation of crops, serves to bring his actions into concord with certain of the actions going on around him. The rational deductions by which the educated navigator calculates his position at sea, imply a series of mental acts by which his proceedings are conformed to surrounding circumstances. Alike in the simplest inferences of the child, and the most refined ones of the man of science, we may recognize this same fundamental correspondence between the simultaneous and successive changes in the organism, and the coexistences and sequences in its environment.
§ 119. Before proceeding to develope this general formula, which, as we have seen, comprehends equally the lowest processes of plant-life and the highest manifestations of human intelligence, I must dispose of a few unimportant objections that may be urged against it.
In the first place, there are still a few inorganic actions apparently included within the definition; as for example that displayed by the storm-glass. The feathery crystallization, which, on the approach of atmospheric disturbance, takes place in the solution contained in this instrument—a crystallization said to assume this or that character according to the nature of the impending change, and which afterwards dissolves to reappear in new forms under new conditions—may be held to present simultaneous and successive changes that are to some extent heterogeneous, that occur with some definiteness of combination, and, above all, occur in correspondence with external changes. It must be admitted that in this case vegetable life is simulated to a considerable extent; but it is merely simulated. Were there no more conclusive mode of meeting the objection, it might be needful to dwell on the fact, that the simultaneous and successive changes here exhibited, consisting solely of modifications of form and atomic arrangement, are neither so numerous nor so heterogeneous as those going on in a plant, which is ever undergoing not only structural modifications, but also those modifications constituting assimilation, circulation, and respiration. It might be needful to dwell on the further fact, that though the changes occur with a certain definiteness of combination, yet that the combination is not so definite as in the plant, either in respect to the form produced, the time occupied in its production, or the time during which it lasts. And once more it might be requisite to urge, that as, though fulfilling the definition in this imperfect manner, these changes so far resemble vital ones that were it not for the great difference in chemical and other conditions we might confound the two, the definition must not be blamed for seeming to include what seems very much like life. But the proper and conclusive reply is, that the relation between the phenomena occurring in the storm-glass and in the atmosphere respectively, is really not a correspondence at all, in the proper sense of the word. Outside there is a certain change; inside there is a change of atomic arrangement: outside there is another certain change; inside there is another change of atomic arrangement. But subtle as is the dependence of each internal upon each external change, the relation between them does not, in the abstract, differ from the relation between the motion of a straw and the motion of the wind that disturbs it. In either case a change produces a change, and there it ends. As with every inanimate object whose state has been altered by an alteration in the environment, the alteration undergone by the object does not tend to produce in it a secondary alteration, in anticipation of some secondary alteration in the environment. But in every living body there is a tendency towards secondary alterations of this nature: and it is in their production that the correspondence consists. To express the difference by means of symbols:—Let A be a change in the environment; and B some resulting change in an inorganic mass. Then A having produced B, the action ceases. Though the change A in the environment, is followed by some consequent change a in it, no parallel sequence in the inorganic mass simultaneously generates in it some change b. But if we take a living organism, and let the change A impress on it some change C; then, whilst in the environment, A is occasioning a, in the organism C will be occasioning c: of which a and c will show a certain concord in time, place, or intensity. And whilst on the one hand, it is in the continuous production of such concords or correspondences that the life consists; it is on the other, by the continuous production of them that the life is made possible.
The further criticisms that may be expected, refer to certain verbal imperfections in the definition, which it seems impossible to avoid. It may be said with truth, that the word correspondence, will not include, without straining, the various relations to be expressed by it. It may be asked:—How can the continuous processes of assimilation and respiration, correspond with the coexistence of food and oxygen in the environment? or again:—How can the act of secreting some defensive fluid, correspond with some external danger which may never occur? or again:—How can the dynamical phenomena constituting perception, correspond with the statical phenomena of the solid body perceived? The only reply to these questions, is, that we have no word sufficiently general to comprehend all forms of this relation between the organism and its medium, and yet sufficiently specific to convey an adequate idea of the relation; and that the word correspondence seems the least objectionable. The fact to be expressed in all cases, is, that certain changes, continuous or discontinuous, in the organism, are connected after such a manner that, in their relative amounts, or variations, or periods of occurrence, or modes of succession, they have a manifest reference to external actions, constant or serial, actual or potential—a reference such that a definite relation amongst any members of the one group, implies a definite relation amongst certain members of the other group; and the word correspondence appears the best fitted to express this fact.
§ 120. And here this presentation of the phenomena under the general form of relations, suggests that before closing the chapter, it will be well to point out how this definition of life may be reduced to its most abstract shape, and its perhaps most perfect shape. By regarding the respective elements of the definition as relations, we may avoid both the circumlocution and the verbal inaccuracy; and that we may so regard them with propriety is obvious. If a creature's rate of respiration is increased in consequence of a decrease of temperature in its environment; it is that the modified relation between the quantity of heat and the quantity of oxygen in the environment, is met by a modified relation between the amount of oxygen absorbed and heat retained, by the creature. If a sound or a scent wafted to it on the breeze, prompts the stag to dart away from the deer-stalker; it is that there exists in its neighbourhood, a relation between a certain sensible property and certain actions dangerous to the stag, while in its organism there exists an adapted relation between the impression that this sensible property produces, and the actions by which danger is escaped. If a long course of inquiry has led the chemist to a law, enabling him to tell how much of any one element will combine with so much of another; it is that the course of inquiry has established in him specific mental relations, which accord with specific chemical relations in the things around. Hence then, as in all cases we may consider the external phenomena as simply in relation, and the internal phenomena also as simply in relation; the broadest and most complete definition of life will be—The continuous adjustment of internal relations to external relations.
At the same time that it is simpler and briefer, this modified formula has the further advantage of being somewhat more comprehensive. To say that it includes not only those simultaneous and sucessive changes in an organism which correspond to coexistences and sequences in the environment, but also those structural arrangements which enable the organism to adapt its actions to those in the environment, may perhaps be going too far; for though these structural arrangements present internal relations adjusted to external relations, yet the continuous adjustment of relations can scarcely be held to include a fixed adjustment already made. But while this antithesis serves to keep in view the distinction between the organism and its actions, it at the same time draws attention to the fact, that if the structural arrangements of the adult organism are not properly included, yet the developmental processes by which those arrangements were established, are included. For it needs but to contemplate that evolution of the embryo during which the organs are fitted to their prospective functions, to at once see, that from beginning to end it is the gradual, that is, continuous, adjustment of internal relations to external relations. Add to which fact the allied fact, that those structural modifications by which the adult organism becomes better adapted to its conditions—those structural modifications which, under change of climate, change of occupation, change of food, slowly bring about some rearrangement in the organic balance—must similarly be regarded as continuous adjustments of internal relations to external relations. So that not only does the definition, as thus expressed, comprehend all those activities, bodily and mental, which constitute our ordinary idea of life; but it also comprehends, both those processes of growth by which the organism is brought into general fitness for these activities, and those after-processes of adaptation by which it is specially fitted to its special activities.
Nevertheless, superior as it is in simplicity and comprehensiveness, so highly abstract a formula as this, is scarcely fitted for our present purpose. Reserving its terms for such use as occasion may dictate, it will be best commonly to employ its more concrete equivalent—to consider the internal relations as “simultaneous and successive changes;” the external relations as “coexistences and sequences;” and the connection between them as a “correspondence.”
THE DEGREE OF LIFE VARIES AS THE DEGREE OF CORRESPONDENCE.
§ 121. Already it has been shown respecting each of the other qualifications included in the foregoing definition, that the life is high in proportion as that qualification is well fulfilled; and it is now to be remarked, that the same thing is especially true respecting this last qualification—the correspondence between internal and external relations. It needs only to consider for a moment, the meaning of the correspondence, to render this fact certain, à priori. For if, as is manifest, the state of an organism is constantly affected by the state of its environment—if, as we know to be the fact, the changes of temperature, of composition, of hygrometric state, in the environment, as also those mechanical actions, and those variations of available nutriment which occur in it, are liable to stop the processes going on in the organism; and if, as is seen in the instances hourly afforded, the changes that take place in the organism have the effect of directly or indirectly counter-balancing these changes in the environment; then, it follows that the life of the organism will be short or long, low or high, according to the extent to which changes in the environment, are met by corresponding changes in the organism. Allowing a margin for perturbations, the life will continue only while the correspondence continues; the completeness of the life will be proportionate to the completeness of the correspondence; and the life will be perfect only when the correspondence is perfect. Not to dwell in general statements however, let us contemplate this law under its more concrete aspects.
§ 122. Looking at life in its lowest developments, we find that only the most prevalent coexistences and sequences in the environment, have any simultaneous and successive changes corresponding to them in the organism. The vital processes going on in a plant, display adjustment solely to the continuous coexistence of certain elements surrounding its roots and leaves; and vary only with the variations produced in these elements by the sun—are wholly unaffected by the countless mechanical and other changes occurring around; save when accidentally arrested by these. The life of a worm is made up of actions referring almost exclusively to the tangible properties of surrounding things: all those visible and audible changes which happen near it, and are connected with other changes that may presently destroy it, pass unrecognised—produce in it no adapted changes: its only adjustment of internal relations to external relations of this order, is seen when it escapes to the surface on feeling the vibrations produced by an approaching mole. Answering as do the proceedings of a bird to an immense number of coexistences and sequences in the environment, cognizable by sight, hearing, scent, and their combinations; and numerous as are the dangers it shuns, and the needs it fulfils, in virtue of this extensive correspondence; it exhibits no such actions as those by which a human being counterbalances variations in temperature and supply of food, consequent on the seasons—no actions such as those by which a human being entraps the prey he cannot run down. And when we see the plant eaten, the worm trodden upon, the bird dead from starvation; we see alike that the death is an arrest of such correspondence as existed; that it occurred when there was some change in the environment to which the organism made no answering change; and that thus, both in shortness and simplicity, the life was incomplete in proportion as the correspondence was incomplete. Evidently, if, as in those lowest organisms classed as protophyta and protozoa, the simultaneous and successive changes show an adjustment only to the most general coexistences and sequences in the surrounding medium; destruction will ensue when there occurs one of those less general coexistences or sequences to which no action in the organism responds. And evidently the progress towards more prolonged and higher life, will be seen in the ability to respond to such less general coexistences and sequences. Every step upwards must consist in adding to the previously-adjusted relations which the organism exhibits, some further relation parallel to a further relation in the environment. And the greater correspondence thus established, must, other things equal, show itself alike in greater complexity of life, and greater length of life—a truth which will be duly realized on remembering that enormous mortality which prevails among lowly-organized creatures, and that gradual lengthening of individual life and diminution of fertility which we meet with on ascending to creatures of higher and higher development.
To avoid misconstruction, it may be well here to remark, that though length of life and complexity of life, are, to a great extent, associated—though a more extended correspondence in the successive changes commonly implies increased correspondence in the simultaneous changes; yet it is not uniformly so. If we contrast the two great divisions of life—animal and vegetable—we find that this relation by no means holds. A tree may live a thousand years, though the simultaneous changes going on in it correspond only to the few chemical affinities in the air and the earth, and though its serial changes correspond only to those of day and night, of the weather, and of the seasons. A tortoise, though exhibiting in a given time nothing like the number of internal actions corresponding with external ones, that are exhibited by a dog, yet lives far longer. The tree by its massive trunk, and the tortoise by its hard carapace, are saved the necessity of responding to those many surrounding mechanical actions which organisms not thus protected must respond to or die; or rather—the tree and the tortoise display in their structures, certain simple statical relations adapted to meet an infinity of dynamical relations external to them. Notwithstanding, however, the sundry qualifications which these two cases will suggest, it needs but to compare a microscopic fungus with an oak, an animalcule with a shark, a mouse with a man, to recognize the general truth of the position, that this increasing correspondence of its changes with those of the environment, which characterizes progressing life, shows itself at the same time in continuity and in complication.
But it is, after all, unnecessary to insist upon this connection between length of life and complexity of life; seeing that, even were it not as conspicuous as it is, it would still be true that the degree of life varies with the degree of correspondence. For if the lengthened existence of a tree, be looked upon as tantamount to a considerable degree of life; then it must be admitted that its lengthened display of correspondences is tantamount to a considerable degree of correspondence. If otherwise it be held, that notwithstanding its much shorter existence, a dog must rank above a tortoise in degree of life because of its superior activity; then it is implied that its life is higher, because its simultaneous and successive correspondences are more complex and more rapid—because the correspondence is greater. And if, lastly, it be remembered, that we regard as the highest life, that which, like our own, shows great complexity in the correspondences, great rapidity in the succession of them, and great length in the series of them; we shall see it to be rigorously true that the degree of life varies as the degree of correspondence.
§ 123. For the further elucidation of this general truth, and especially for the explanation of the irregularities just referred to, it requires to be observed, that as the life becomes higher the environment itself becomes more complex. Though, in its largest acceptation, the environment must be held to mean all surrounding space with the coexistences and sequences contained in it; yet, practically, it often means but a small part of this. The environment of an entozoon can scarcely be said to extend beyond the body of the animal in which it lives: that of a freshwater alga is, virtually, limited to the ditch it floats in. And understanding the term in this restricted sense, we shall see that the superior organisms inhabit the more variable environments.
Thus, regarding it in the mass, the lowest life is that found in the sea; and it has the simplest environment. Marine creatures are affected by no such multiplicity of coexistences and sequences as terrestrial ones. Being very nearly of the same specific gravity as the surrounding medium, they have not to contend with those various mechanical actions which mammals and birds are subject to in their motions on the earth and through the air. The zoophyte rooted to a stone, and the acalephe passively borne along in the current, need to undergo no internal changes such as those by which the caterpillar meets the varying effects of gravitation while creeping over and under the leaves. Again, this aboriginal environment—this environment to which all the earliest forms of life known to geologists belong—is liable to none of those marked alterations of temperature which the air suffers. Night and day produce no appreciable modifications in it; and it is but little affected by the seasons. Thus its contained fauna show no marked correspondences similar to those by which air-breathing creatures counterbalance thermal changes. Again, in respect to the supply of nutriment the conditions are far more simple. The lower tribes of animals inhabiting the water, like the plants inhabiting the air, have their food brought to them. The same current which brings oxygen to the oyster, also brings it the microscopic organisms on which it lives: the disintegrating matter and the matter to be integrated, coexist under the simplest relation. But it is otherwise with land animals. The oxygen is everywhere; but that which is needed to neutralize its action is not everywhere; it has to be sought; and the conditions under which it is to be obtained are more or less complex. So again with the fluid by whose agency only, the vital processes can be carried on. To marine creatures, water is ever present; and by the lowest is passively absorbed: but to most creatures living on the earth and in the air, it is available only after they have undergone those nervous changes constituting perception, and those muscular ones by which drinking is effected. Similarly, the contrast might be continued with respect to the electric and hygrometric variations, and the greater multiplicity of optical and acoustic phenomena with which terrestrial life is surrounded. And tracing upwards from the amphibia the widening extent and complexity which the environment, as practically considered, assumes—observing further how that gradually-increasing heterogeneity in the flora and fauna of the globe, which time has produced, has itself progressively complicated the environment of each species of organism—it might finally be shown that the same general truth is displayed in the history of the human race: whose advance in civilization has been simultaneous with their advance from the less varied requirements of the torrid zone to the more varied requirements of the temperate zone; whose chief steps have been made in regions presenting a complicated physical geography; and who, in the course of their progress, have been adding to their physical environment a social environment that has been growing even more involved. Thus, neglecting details, it is clear that as an average fact, those relations in the environment to which the relations in the organism must correspond, themselves increase in number and intricacy as the life assumes a higher form.
§ 124. As tending to bring into yet clearer view the fact that the degree of life varies as the degree of correspondence, I may here point out, that those other qualifications which were successively introduced when seeking to distinguish vital changes from non-vital changes, are all implied in this last qualification—their correspondence with external coexistences and sequences; and further, that the peculiarity seen in each of those qualifications—namely, that the higher the life the more it is fulfilled—is involved in the analogous peculiarity of this last qualification—namely that the life is high in proportion as the correspondence is great. To descend to particulars:—We saw that living organisms are characterized by successive changes; and that as the life becomes greater, the successive changes become more numerous. Well, the environment is full of successive changes, both positive and relative; and the more complete the correspondence, the greater the number of successive changes an organism must display. We saw that life presents simultaneous changes; and that the more elevated it is, the greater the multiplicity of them. Well, besides the countless phenomena of coexistence, there are often many changes occurring at the same moment in the environment; and hence increased correspondence with it, presupposes an increased display of simultaneous changes in the organism. So, too, is it, with the heterogeneity of the changes. In the environment the relations are extremely varied in their kinds; and hence, as the organic actions come more and more into correspondence with them, they also must become extremely varied in their kinds. So again is it, even with definiteness of combination. For though the inorganic bodies of which the environment mainly consists, do not present definitely-combined changes, yet they present definitely-combined properties; and though the minor meteorological changes of the environment do not show much definiteness of combination, yet those resulting from day and night and the seasons do. Add to which, that as the environment of each organism comprehends all those other organisms existing within its sphere of life; as the most important and most numerous changes in the environment, with which each creature has to deal, are the changes exhibited by other creatures, whether prey or enemies; and as these changes are in more or less definite combination; it results that definiteness of combination is a general characteristic of the external changes with which internal ones have to correspond. Hence, increase of correspondence involves increased definiteness of combination. And thus it is manifest that throughout, the correspondence of the internal relations with the external ones is the essential thing; and that all the special characteristics of the internal relations, are but the collateral results of this correspondence.
§ 125. As affording perhaps the simplest and most conclusive proof that the degree of life varies as the degree of correspondence, it remains but to point out that perfect correspondence would be perfect life. Were there no changes in the environment but such as the organism had adapted changes to meet; and were it never to fail in the efficiency with which it met them; there would be eternal existence and universal knowledge. Death by natural decay, occurs because in old age the relation between the integrating and disintegrating processes going on in the organism, gradually falls out of correspondence with the relation between oxygen and food in the environment; and eventually the disintegrating process gets so far in advance, that the organism becomes unfit to act. Death from disease, arises either when the organism is congenitally defective in its power to balance the ordinary external actions by the ordinary internal actions, or when there has taken place some unusual external action to which there was no answering internal action. Death from accident, implies some neighbouring mechanical changes whose antecedents are either unobserved from lack of attention, or are so intricate in their dependencies that their consequences cannot be foreseen. In each of these cases the relations in the organism fail in their adjustment to the relations in the environment. Manifestly, if, to every outer coexistence and sequence by which it was ever in any degree affected, the organism presented an answering process or act; the simultaneous changes would be indefinitely numerous and complex, and the successive ones endless—the correspondence would be the greatest conceivable, and the life the highest conceivable, both in degree and in length.
§ 126. And now we may fitly proceed to study the gradual evolution of this correspondence, as seen in progressing from low to high types of life. Those more complex forms of internal change which constitute the subject matter of Psychology, cannot be adequately comprehended without a previous comprehension of those simple forms of it which constitute life in its unintelligent phases. Fundamentally determined, as both these classes of vital relations are, by relations in the environment; and insensibly developed as we shall find the one class to be out of the other; we must take a general view of the entire series of facts, before attempting to interpret the latter part of the series.
Even in the prosecution of this preparatory inquiry, we shall find it needful to arrange the phenomena into groups. Indivisible as they really are, their multiplicity, variety, and complication, is such, that they cannot be truly seen from any one point of view; but must be contemplated under a succession of different aspects.
I may further premise that some of the illustrations and subordinate statements, by which the general argument is elucidated, must be taken with a certain latitude. The phenomena of Life are so complicated, and the modifications of them that occur under modifications of conditions, so various, that duly to substantiate each example of the application of any universal principle, requires preliminaries and qualifications specially referring to the peculiarities of the case; and to give these in every instance would inconveniently encumber the argument. Rather than do this, I prefer leaving those who have a critical knowledge of the facts, to recognize for themselves the occasional imperfections of statement; and to perceive, as I think they will, that these do not militate against the substantial truth of the proposition to be established. I will add, that while there are sundry instances in which, rather than confuse the argument, I have purposely omitted qualifications that might readily be supplied; there are possibly others in which I have unwittingly fallen into error. My acquaintance with physiology is simply that of an amateur; and in a science so extensive, and now undergoing such rapid development, only those who devote their whole time to it can be sure of all their statements. The truth of the doctrines enunciated, however, will be found quite independent of errors in detail, if such there be.
THE CORRESPONDENCE AS DIRECT AND HOMOGENEOUS.
§ 127. As the highest life is found in the most complicated environments, so, conversely, the lowest life is found in environments of unusual simplicity. Most environments present both coexistences and sequences; but there are some that during a limited period, present coexistences only; and in these, during this limited period, occur the organic forms to which, by common consent, is assigned the lowest place, both in respect of structure and vital properties. Of those classed with the vegetable kingdom, may be instanced the yeast-plant, and the Protococcus nivalis (red snow fungus). Of those held to be of animal nature, the Gregarina, and the parasitic cell which causes smallpox, may be taken as samples. The life of each of these organisms consists, almost wholly, of a few cotemporaneous processes in correspondence with the coexistent properties of the medium which surrounds it. The yeast-plant has for its habitat, a fluid consisting of water holding in solution certain hydrocarbons, some nitrogenous matter, oxygen, and probably other elements in minor proportions. That it may flourish, the temperature must be maintained within certain limits, and light must be excluded. These conditions being fulfilled, the yeast-plant displays what we call vital changes, in correspondence with the chemical changes of the elements bathing its surface—the cell grows; the fluid ferments: and while the fluid continues to supply the needful materials under the needful conditions, the cell continues to display the same phenomena. But let the temperature be considerably raised, or some of the ingredients exhausted, and the respective actions cease. The life, limited in length to the brief period during which the environment remains practically uniform, exhibits no successive changes such as those by which a shrub responds to the alternations of day and night, of the seasons, of the weather. Excluding those modifications of form and size which are the necessary concomitants of continued assimilation, the only successive changes which the yeast-plant displays, in common with the higher plants, are those which result in the formation of spores. Dependent as they possibly are upon those alterations of the environment which continued fermentation produces—perhaps partly determined by the diminishing quantities of the materials needful for growth—these generative actions may be regarded as successive changes corresponding with successive changes in the environment; and most likely there is no organism but what, in addition to the simultaneous processes taking place in it, undergoes a serial process of this character. Evidently, however, the two orders of change, answering in this case to the two all-essential functions of assimilation and reproduction, exist under their simplest forms, in correspondence with the simplest relations in the environment; and ending as they do with that new state of the environment soon arising, the life is as short as it is incomplex.
It is needless to present in detail each of the other cases referred to. Substantially, they are severally of the same nature as the foregoing one. The Protococcus nivalis exists only in snow—a medium simple and constant in chemical character; confined in its variations of temperature; and which only under still more special conditions than those common to it, contains this microscopic fungus. Propagating itself over large tracts in the arctic regions in the course of a single night, during which the surrounding circumstances must remain almost uniform, this minute organism exhibits vital processes corresponding only to the surrounding coexistences; and can undergo scarcely any changes corresponding to surrounding sequences. To a new state in its medium, it does not adapt itself but dies: the snow melts and it disappears. Similarly with the Gregarina—a single-celled creature which inhabits the intestines of certain insects; which is bathed by the nutritive fluid it assimilates; which is kept at a tolerably constant temperature; and which can continue to exist no longer than its special environment exists. And so too with the organic monads which constitute the virus of smallpox—monads which live in the blood; which multiply at the expense of certain of its constituents; which are preserved by it in conditions liable to little variation; and which cease to exist when their habitat has undergone that slight modification which the disease causes in the constitution. In all these cases the peculiarities to be noted are:—first, that the actions in the organism are in immediate dependence upon the affinities of the elements touching it on all sides; and second, that the internal processes of change proceed uniformly, or nearly so, because, during the brief time that the life lasts, the external relations remain uniform, or nearly so. The correspondence is at once direct and homogeneous. The disintegrating matter and the matter to be integrated, being everywhere diffused through the environment, it results that all the agents to which the vital changes stand related, are not only in contact with the organism, but continuously in contact with it. And hence the reason why there need neither those motions nor locomotions, which, where they are found, involve more or less heterogeneity in the correspondence.
§ 128. In strictness, no other forms of life than those of the kind just described, can be said to exhibit a correspondence at once direct and homogeneous. But the transition to higher forms is so gradual, that in making groups, it is impossible to avoid incongruities; and on the whole, it seems best to notice here a class of organisms, which, while they exhibit motion, either positive or relative, do so with comparative uniformity—a uniformity which implies that the correspondence is almost as homogeneous as in the cases above given. The ciliated spores of the algæ; the simplest of the ciliated animalcules; the most regular of the compound ciliated organisms, as the Volvox globator; together with the sponges and their allies; may be instanced as displaying this order of life.
Water, either fresh or salt, being in all these cases the medium inhabited, the general fact to be observed, is, that the incipient heterogeneity in the vital actions, is in correspondence with the incipient heterogeneity of the environment. Though, from a human point of view, the fluids in which the yeast-plant and the Gregarina live, are far more heterogeneous than the water, either of the sea or of a pond; yet, relatively to these contained organisms, they are less so. For whilst on the one hand, every portion of the wort bathing the cell-wall of the yeastplant, and every portion of the nutritive emulsion surrounding the Gregarina, presents the matter to be assimilated; on the other hand, every portion of the water in which a protozoon swims, though it presents oxygen, does not always present nutriment. In a concentrated form as the food of the first is, and in a dispersed form as is that of the last; it is clear that the external relations must be more homogeneous to the one than to the other. And manifestly, an organism whose medium is unceasingly disintegrating it, but is not unceasingly supplying it with integrable matter, but only presents scattered atoms of such integrable matter, must either traverse its medium with such velocity as shall bring it in contact with the requisite quantity of integrable matter, or must cause the medium to move past it with the like velocity—must either have a positive motion, as the infusory animalcule, or a relative motion, like that of the sponge towards the current of seawater it draws in and expels. Thus then, the addition of mechanical change to the changes displayed by motionless organisms, is the addition of new internal relations in correspondence with new external relations.
Further, it is to be remarked, that the processes by which the movement is effected, are themselves in direct and almost homogeneous correspondence with certain almost ever-present properties of the environment. The fact that the ciliary action of fresh-water creatures ceases when they are put into sea water, and that of sea-water creatures when they are put into fresh water; joined with the fact that when the creatures displaying it have been killed, the ciliary action on the uninjured parts, and even on parts that have been cut off, continues for a long time; and joined with the further fact, discovered by Virchow, that ciliary motion, which has ceased, may be reproduced by a solution of caustic potash; suffice to show, that the motion of these microscopic hairs is caused by the immediate contact of some matter or agent in the environment—consists of a succession of minute internal changes, in correspondence with those minute recurring actions of the medium which the waving of the cilia themselves involve. And the occasional suspensions and reversals of the motion, commonly so sustained, may possibly result from local deficiencies in the medium, of those materials or conditions that determine it; in which case, this slight heterogeneity in the mechanical changes, is in correspondence with a slight heterogeneity in the environment.
Other tribes of marine creatures, as the Thalassicola, display types of correspondence somewhat unlike the foregoing in character, though differing little in degree. But it is unnecessary to do more than indicate them.
THE CORRESPONDENCE AS DIRECT BUT HETEROGENEOUS.
§ 129. The advance, of which we have just marked the first steps, from a correspondence that is uniform to one that is varied, begins to show itself distinctly, under either an absolute or a relative change in the environment. In the case of plants, it is seen when, from a habitat in which the elements are not only ever-present in immediate contact with the organism, but ever in a fit condition for absorption by it, we pass to a habitat in which the needful elements, though ever present, are not always in a fit condition for absorption. And in the case of animals, it is seen both on passing from the protozoa to the larger aquatic creatures, which by their increased size and consequent necessity for larger prey are in the condition of having their nutriment less uniformly diffused, and on passing from aquatic creatures to terrestrial ones, to which the less uniform diffusion of nutriment is not relative only, but absolute. In all these instances the result is, that in addition to a correspondence with ever-present coexistences in the environment, we have now a correspondence to certain sequences in it. Let us glance at each class of cases.
§ 130. In the higher plants, which require not only carbonic acid and oxygen, but light, a certain temperature, a certain soil, and a certain quantity of moisture, we find variations in the vital actions corresponding with the variations which the environment undergoes in respect to these conditions—variations corresponding with those of the hour, the weather, and the seasons. As we lately saw, the lowest life continues only so long as its environment remains practically homogeneous, both in Space and Time. The next highest order of life must be looked for in organisms displaying correspondence with the most general changes to which the environment is liable: and this is the kind of life which the vegetable kingdom at large exhibits. These changes in quantity of light and heat, are not only most general as occurring with greater regularity in time and degree than any others, but also as affecting the whole mass of the medium by which the organism is surrounded. And thus, in virtue both of their periodicity and universality, as well as by their comparative slowness, they produce only that small degree of heterogeneity in the environment, to which the small degree of heterogeneity in the visible changes of plant-life corresponds.
It should be further remarked, that the greater complexity of correspondences, and therefore greater length in the series of correspondences, which these higher plants display, involves an additional group of vital processes necessitated by increase of size. The long-continued growth rendered possible by this completer adjustment of internal relations to external relations, implying, as it does, a greater and greater remoteness in the parts of the organism from each other, supposes some means whereby these remote parts shall be put in communication; and hence a circulatory system. Or perhaps it may more strictly be said, that a circulatory system is necessitated by increase of size, joined with the division of the environment into the two halves, soil and air; and if so, the only respect in which the plant displays mechanical action, must be regarded as in correspondence with the only respect in which the elements in its environment are not coextensive in Space.
§ 131. Turning from plants to plant-animals (zoophytes), we see that while in them, there are certain general successive changes corresponding like those of plants with general successive changes in their environment, they more manifestly exhibit certain special changes, corresponding with special changes in it. While to the chemical, thermal, and hygrometric actions affecting the whole mass of its surrounding medium, the actions going on in the plant slowly respond; there is no response in it to the surrounding mechanical actions: as those of a wire-worm gnawing its roots; or a herbivore browsing on its leaves. On the other hand, the most conspicuous of the actions seen in a zoophyte, are those that result when its expanded tentacles are touched. To a relation of coexistence between tangible and other properties, presented in a particular part of the environment, there corresponds, in the organism, a relation of sequence between certain tactual impressions and certain contractions. Here there are several facts to be noticed. First, that being a stationary creature, whose medium does not supply matter to be integrated so uniformly as it supplies disintegrating matter, there arises the necessity, that the creature must obtain matter to be integrated, either by filtering out of its medium the minute portions it contains (as do those zoophytes and molluscs that absorb and expel currents), or by arresting those larger portions here and there moving through its medium; and to do this last, presupposes sensitiveness and contractility connected in the manner seen. Second, that the ability to respond, not simply to the coexistences and sequences presented by the whole mass of the environment, but to the coexistences and sequences presented by particular bodies in it, is an advance in the degree of correspondence. And third, that as these particular bodies, exhibit in virtue of their motions much more various changes than those which the environment in general undergoes, an increased heterogeneity in the correspondence is at the same time involved.
§ 132. Of all these cases however, it is to be remarked, as of those in the last chapter, that the correspondence between internal and external relations, extends only to those external relations which occur in absolute contact with the organism. Not only is it that the processes going on in the yeast-plant, cease, unless its cell-wall is bathed by the saccharine and other matters on whose affinities they depend; not only is it that the tree must have its carbonic acid, water, earthy salts, ammonia, and the rest, applied directly to its surface in the presence of light and heat, and that until they are thus applied it remains inert; but it is, that in the lowest division of the animal kingdom also, the substances to be assimilated must come in collision with the organism before any correspondence between inner and outer changes is shown. Alike in those forms of life whose environment perpetually presents the disintegrating and integrable matters under the requisite conditions; those whose environment perpetually presents them, but under variable conditions; those whose environment, though not full of integrable matter, yet contains it in such abundance that mere random locomotion brings them in contact with a sufficiency; and those whose environment contains it in moving masses of such number, that though themselves stationary, chance brings them as many as they want—alike in all these forms of life, there is an absence of that correspondence between internal relations and distant external relations, which characterizes more highly-endowed organisms.
THE CORRESPONDENCE AS EXTENDING IN SPACE.
§ 133. On ascending from the lowest types of life, in which the adjustment of inner to outer relations is thus limited, one of the aspects under which heightening correspondence shows itself, is the increasing distance at which coexistences and sequences in the environment can produce adapted changes in the organism. This progress takes place simultaneously with the development of the senses of smell, sight, and hearing; and ultimately of the higher faculties.
There is every reason to believe, that the susceptibilities to odours, colours, and sounds, arise by insensible degrees out of that primordial irritability with which animal tissue in its lowest forms, is uniformly, or almost uniformly, endowed. The saying of Democritus, that all the senses are modifications of touch, modern science goes far to confirm. The sense of smell is very obviously one which implies the contact of dispersed particles with a specially-modified part of the organism—is a sense which becomes operative, only when these particles are so carried by a current of air or water as to impinge upon this modified part. The sense of hearing is one by which we feel the vibrations of the air lying in contact with our bodies. As the skin at large is sensitive to a succession of mechanical impulses given by matter of some density; so, through that specialized portion of the skin known as the ear-drum, we are sensitive to a far more rapid succession of mechanical impulses given by matter of much greater tenuity. The sense of sight, again, is one by which the pulses or undulations of a yet more delicate medium are impressed upon us—undulations incomparably more rapid in a medium incomparably rarer. Here however, as before, a contact of the undulating medium with an adapted part of the surface, is the pre-requisite to any impression. Hence in all cases, the sensations produced in us by things in the environment, really involve the mechanical action of some order of agency upon some part of our surface. In all cases if the vibrating, or moving, or resisting substance, be prevented from coming in collision with that part of the surface fitted to appreciate it, there is no sensation. In all cases therefore, touch, of a more or less refined order, is implied. Not only is it, however, that the conclusions of physicists afford support to this doctrine which Democritus taught; but it is that the conclusions of physiologists do the like. The organs of the special senses are every one of them developments of the dermal system—are modifications of that same tissue in which the tactual sense in general is seated. Nor is this all. It is a remarkable fact, which I state on the authority of one of our first physiologists, that the eye and the ear both exhibit a type of structure fundamentally the same with that seen in the vibrissœ, or most perfect organs of touch. Thus, whether the matter be considered anatomically, or physiologically, or physically, the inference is the same.
There are not wanting evidences that the senses in general have a yet deeper basis in those primordial properties of organic matter which distinguish it from inorganic matter. It is a conclusion to which many facts point, that sensibility, of all kinds, tactual and other, takes its rise out of those fundamental processes of assimilation and oxidation—integration and disintegration—in which Life, in its primitive form, consists. Though these facts cannot be held sufficient to establish such a conclusion, which must be regarded as more or less speculative; and though it is not necessary to the general argument that they should be here given; yet, they form so appropriate an introduction to the subject of the chapter—the extension of the correspondence in Space—that it will be desirable to devote a section to them.
§ 134. In the lowest members of the animal kingdom, whose bodies are so little organized as to be almost, if not quite, homogeneous, the whole mass of tissue performs, in its imperfect way, all the vital functions. Every part exhibits more or less of that contractility which in higher creatures is confined to the muscles; that irritability which they show only in the nerves; that reproductive power which with them is localized; that absorption of oxygen which only their lungs perform; that power to assimilate which is eventually confined to the stomach; that excretory action afterwards divided among the lungs, skin, and kidneys. Where, as in the lowest creatures of all, the body consists of nothing more than a structureless, homogeneous, substance; and where, as in somewhat higher and larger creatures, the body is made up of little else than an aggregation of like cells, there is an almost complete community of functions throughout: and only as fast as the structure comes to be specialized, does each part lose the power of subserving other processes than its habitual one.
To this general truth should be added the supplementary one, that in a great majority of cases, if not throughout, the specialization of functions which progresses pari passu with vitality, never entirely obliterates this aboriginal community of functions. Even where “the physiological division of labour” has been carried to the greatest extent, most, if not all, of the tissues, retain a certain power of fulfilling each other's duties. In the human being, skin can discharge the office of mucous membrane; and mucous membrane of skin. Lungs and kidneys can to some extent supply each other's shortcomings. Upon emergency, muscle can secrete a species of integument in place of that which the dermal system usually supplies. In salivation, the glands of the mouth become supplementary excreting organs. And the skin, while having mainly the function of ejecting perspirable matter, yet remains, to some extent, both a respiratory surface, and an assimilatory surface.
Bearing in mind then these general facts, that throughout the organic or, as physiologists term it, the vegetative life—the life made up of unintelligent processes—bearing in mind that throughout this division of life, heterogeneity of structure and function arise out of an aboriginal homogeneity, the traces of which are never entirely lost; we shall be prepared to find a certain parallelism of method and results, in the evolution of that other division of life, consisting of the sensory and motor actions. Here, too, we may look for a certain community of function throughout the whole organism—a possession by the whole organism of those susceptibilities which are ultimately located and developed in eyes, ears, nose, and the rest. The primordial tissue, which, by one process of differentiation and integration, gives origin to the internal and external systems—the visceral and nervo-muscular organs—must possess, to some extent, the powers of the last as well as of the first. Not only the fundamental separation into vegetative and animal functions, but the subdivision of each of these into all the minor processes and actions, must be regarded as so many specializations of the various properties which every part of the elemental tissue possesses in some slight degree. Let us glance at the genesis of the several senses from this point of view.
Between touch and assimilation, there exists, in the lowest animal forms, an intimate connection. Not only does assimilation necessarily presuppose touch; but, among the simplest protozoa, touch and assimilation are to a considerable extent coextensive: the tactual surface and the digestive surface are the same. The Amœba, a structureless speck of jelly having no constant form, sends out, in this or that direction, prolongations of its substance. One of these prolongations meeting with, and attaching itself to, some relatively fixed object, becomes a temporary limb by which the body of the creature is drawn forward; but if this prolongation meets with some relatively small portion of organic matter, it gradually expands its extremity round this, gradually contracts, and gradually draws the nutritive morsel into the mass of the body, which collapses round it and presently dissolves it. That is to say, the same portion of tissue is at once arm, hand, mouth, and stomach—is at once a sensory, motor, and digestive organ— shows us the tactual and assimilatory functions united in one. And if we assume, as we may fairly do, that the stimulus which causes the contraction of this protruded part when its extremity touches assimilable matter, arises from the chemical relation between the two—is caused by a commencing absorption of the assimilable matter, an incipient digestion of it—we shall see a still closer relation between the primordial sense and the primordial vegetative function.
In the same phenomena we may trace a nascent sense of taste. The ability to discriminate between organic and inorganic matter, appears to be in some degree possessed even by these most lowly of the animal kingdom. The Amæba, the Actinophrys, the Difflugia, and other creatures of this order, do not appear to absorb indiscriminately all fragments of available size; nor do the tentacles of polypes, though their action is by no means uniform, commonly behave in the same way when touched by inorganic bodies as when touched by organic bodies. Evidently, therefore, the primordial tissue must be differently affected by contact with nutritive and with innutritive matters. And bearing in mind that to creatures living in water, the innutritive matters are, generally speaking, the insoluble, and the nutritive the soluble; bearing in mind, further, that in these primordial organisms, all parts perform the digestive function; it becomes highly probable, as above suggested, that the selective power which they appear to possess, is really due to the setting up of an assimilative process when assimilable matter is brought in contact with them, and to the absence of that process when the matter presented is not assimilable. Whence it would follow that this selective power, which is an incipient sense of taste, is, primarily, one aspect of that integrating action which mainly constitutes the life. And we shall see yet further reason for thus interpreting the facts, if we bear in mind that, even in its highest developments, tasting forms one link in the chain of assimilative actions; and that it itself results from a local assimilation. The mouth is part of the alimentary canal, which, throughout its whole extent, secretes digestive fluids and takes up dissolved substances. The mouth does both these: its saliva is a digestive fluid; and in the act of tasting, some of the substances which this digestive fluid dissolves, are absorbed through the mucous membrane of the tongue and palate. Manifestly, therefore, all tasting, considered as a physiological act, is a modified assimilation.
Again, smell has the same root with taste, and remains throughout closely associated with it. In air-breathing creatures there is a tenable division between the two: the one taking cognizance of matters suspended in air; and the other of matters suspended in water. But in creatures inhabiting the water, the two senses can be but relative degrees of the same: the one responding to a more dilute solution of nutritive substance; the other to a more concentrated solution. As the soluble elements which surround a portion of animal matter, and cause a zoophyte to distinguish it, are not confined to the actual surface of such matter, but are diffused in the surrounding water with an abundance that decreases as the distance increases; it is obvious that a greater susceptibility will render the matter appreciable before there is absolute contact; and that so, taste must pass gradually into smell. The intimate connection of taste with smell, and of both with touch, is displayed even in man. The nerves of both are spread out under a membrane that is continuous with, and but a slight modification of, the skin; they lie under adjacent parts of this membrane, close to its junction with the skin; they are so nearly allied in the sensations they give, that, knowing the smell of a substance, we can frequently form an approximate judgment of its taste; and to both, the substances to be recognized, must be presented in solution—the sapid particles either ready dissolved, or dissolvable by the saliva, and the odorous ones condensed by the film of moisture covering the membrane which lines the nose. Thus, even in ourselves, the difference is less between the modes in which the sensations are ultimately produced, than between the forms under which the substances producing them originally exist—liquid or solid in the one case; gaseous in the other. Further, the relationship of the sense of smell to the fundamental organic actions, is traceable, not only through its affiliation upon the sense of taste, but is traceable directly. Not only is it that in low, aquatic creatures, smell and taste must be united by transitions such as those by which we insensibly pass from absolute contact to an appreciable distance in space, and that therefore smell has a common root with taste in the vegetative processes; but it is that even in its highest forms, its connection with them remains visible. The nostrils are simply divergent branches of the alimentary canal, from which, in the embryo, they are not separate; and absorbing into the system, as they do, some of the floating particles given off by the food that is being eaten, or is about to be eaten, their action, too, is but an evanescent form of assimilation. Add to which, that in so far as the olfactory action is not assimilative it is respiratory; and thus, in a sense, lies between the two original vital processes.
Once more, there are facts which indicate that in its initial stages, even the faculty of sight is implicated with the functions of organic life; and that it arises by gradual differentiation from these. The organisms which occupy the border land between the animal and vegetable kingdoms, share with plants the ability to decompose carbonic acid under the influence of light. Water containing protozoa gives off oxygen on exposure to the sun's rays. The link between the two great divisions of living forms, which these lowest creatures present in structure, development, and chemical character, they would also appear to present in their nutritive action. Now, considering this community of nature displayed by these lowest and simplest organisms, it is not an unreasonable expectation, that, on passing from them to vegetable and animal organisms respectively, we shall on the one hand find the ability to decompose carbonic acid by the agency of light, more and more developed, and on the other hand, more and more wanting. Standing alone, this expectation would go for little; but joined with recently disclosed facts, it is significant. Observe, in the first place, that the researches of Schultze go to establish an identity between the colouring matter of the Hydra, Turbellariæ, (and several Infusoria,) and the chlorophyl of plants. And then, in the second place, observe, that the Hydra habitually shuns the light—habitually chooses the dark side of the vessel in which it is placed. Are not these two facts strongly suggestive of the conclusion, that the sensitiveness to light which the Hydra exhibits, results from the action which the light produces in its contained chlorophyl; that this action, being like the action produced in the chlorophyl of plants, is an assimilative action; and that thus, the power which the primordial tissue possesses to distinguish light from darkness—a power which forms the germ of the visual faculty—is the result of a modification produced by light upon the general vital activity? Any doubt that may be felt respecting this hypothesis, will, I think, be greatly diminished, on remembering that even in ourselves, the body in general retains a physiological sensitiveness to light; and that this sensitiveness is of the same order as that described. The darkening of the skin produced by continued exposure to bright sunshine, is nothing else than a modification of the assimilative action going on in the dermal tissues—a change in the absorption of materials supplied by the blood. And as, in transparent and semi-transparent creatures, any alteration in the assimilative action must pervade the whole body; it is easy to understand how the presence of light may produce marked changes in such creatures.
That the faculty of hearing, has, like the others, a root in the primitive vital processes, there is little if any direct evidence. But that in its nascent stage it is dependent upon them, may be suspected from the fact that, to sound as to light, the whole animal organism in its simplest forms, possesses a feeble susceptibility. A sharp blow, causing a vibration to pass through the vessel containing them, is responded to by creatures in whom no sign of a hearing organ exists. And if we call to mind the facts that congenitally deaf persons have acute perceptions of sonorous vibrations in the bodies they touch; and that they can even perceive such vibrations in the air, when produced by a loud concussion, as a cannon shot—if we infer, as we must, that even with ourselves, the whole body is in a certain degree sensitive to sound; that the extreme sensitiveness of one part is simply a specialization of this general sensitiveness; and that it is in consequence of the great strength of the special impression that we cease to be conscious of the general impression—and if we further remember that in so dense a medium as water, the general impression must be much more powerful, especially on organisms much like water in specific gravity, and of lax tissue—we shall have no difficulty in understanding how the humblest zoophytes and molluscs may be distinctly affected by those rapid undulations which constitute objective sound. Such undulations must, in fact, permeate the entire mass of one of these soft-bodied creatures, almost as though it were so much water: and doing this, it can scarcely fail so to disturb the tissues in their ultimate structure, as to produce a marked change in their general state; and some consequent change in the external manifestations. Still it may be asked:—How do these facts tend to affiliate the faculty of hearing upon the aboriginal vegetative processes? I reply:—They tend to do so in so far as they suggest that the contraction produced by any sonorous vibration permeating a zoophyte's body, results from some modification of the vegetative processes. Such evidence as we have on the matter, implies that the life of the almost homogeneous tissue of which these simple creatures consist, is little else than the cumulative result of the lives of its component cells and granules; which severally absorb the nutrient juices percolating among them; are severally bathed by the oxygenating medium; and severally carry on the integrating and disintegrating actions by and for themselves. Now, anything which causes a sudden agitation of the aerating and nutritive fluids diffused through this lax tissue—anything which accelerates the confused circulation of them which we must presume to be going on; will produce a sudden accession of vital activity in all the components of the tissue. A rapid succession of undulations propagated through the mass must do this. And we have but to suppose that the increased vital activity of each component, is accompanied by some change in its form—due, perhaps, to osmotic action, or electricity, or both—to understand how a contraction of the entire creature may result.
Thus, there is not a little reason to think that all forms of sensibility to external stimuli, are, in their nascent shapes, nothing but the modifications which those stimuli produce in that duplex process of assimilation and oxidation which constitutes the primordial life. No part of the tissue of a zoophyte can be touched, without the fluids diffused throughout the adjacent parts being put in motion, and so made to supply oxygen and food with greater rapidity. Nutritive matter brought in contact with the surface, which, in common with the rest of the body, assimilates, must cause a still greater excitement of the vital actions; and so must cause the touch of organic substances to be more promptly responded to than that of inorganic substances. A diffusion of nutritive matter in the form of an odour, will tend in a slight degree to produce analogous effects. The tissue having the requisite chemical nature, light, also, must modify the assimilative actions. And, as just shown, sonorous vibrations probably do the like. We only need to make the very reasonable assumption, that the component parts of these almost unorganized creatures, are severally changed in form by changes in their vital activity—an assumption which the phenomena of endosmose and exosmose, would alone go far to justify—to see that the various sensibilities are rooted in the primordial vegetative life. A liberal interpretation of the facts, serves to confirm the deduction from the universal law of organic progress—the deduction that as the aboriginal tissue out of which, by continuous differentiation and integration, arise the organs of vegetative life, possesses, to some extent, the functional powers of all those organs; so must it, to some extent, possess the functional powers of the organs of animal life, and among them of the senses; which similarly arise out of it by a continuous differentiation and integration. And hence we find reason, not only for thinking with Democritus that the other senses are modifications of the sense of touch; but for regarding all orders of sensibility as developments of the purely physical processes with which life commences.
Closing here these speculations respecting the genesis of the several faculties through which the animal organism holds communication with the external world, let us now go on to our immediate subject—that extension of the correspondence in Space, which takes place simultaneously with the evolution of these faculties.
§ 135. Arising insensibly, as, in aquatic creatures, smell does out of touch and taste, it is not to be expected that in its nascent form it should be detected without careful experiments; and I have not met with any accounts of such. “How far any sense of smell exists in the lower invertebrata, cannot be satisfactorily determined,” says Dr. Carpenter; “but it would seem not improbable that even where no special organ is apparent, some part of the general surface may be endowed with olfactive sensibility.” Certainly, analogy would lead us to suppose, that before the sense of smell is manifestly present, it is present in a less observable degree. But be this as it may, it is clear that only when in some degree localized, does it become a means whereby internal relations can be brought into something like definite correspondence with external relations that do not occur in actual contact with the surface of the body. Supposing, merely for antithesis sake, that, in common with its many other diffused faculties, the organism in general originally possesses a feeble susceptibility to odours; it is manifest that the only correspondence capable of being established by means of it, must be seen in some state of readiness to seize the prey or avoid the enemy, whose proximity an odour implies. Though, by means of such endowment, an inner relation can be adjusted to an outer relation not in actual contact with the surface; yet, there can be no correspondence to relations of either direction in space or distance in space. But when there exists a susceptibility that is to some extent localized, the organism must be differently affected by an odoriferous body, according as it is situated in this or that position; and when, as an accompaniment of specialization, there is increased efficiency, it is clear that a less strongly smelling body coming near to the more highly sensitive tract, may produce a response as great as that which a strong odour pervading its environment, would produce on an organism possessed of a diffused but inferior susceptibility—a response too, displaying some adjustment, both to direction and distance in space.
Passing from these vague beginnings of the olfactory sense, respecting which we as yet lack data for determining anything specific, it will be obvious that in proportion as there is developed at the entrance of the respiratory passages, a definite apparatus capable of being excited by floating particles, organic and other; in the same proportion must there be an extension of the space through which coexistences and sequences in the environment, can establish corresponding coexistences and sequences in the organism. When we trace up the evolution of the faculty to that great perfection in which it is possessed by land animals that hunt by scent, we see that one of the aspects under which the advance presents itself, is, the increasing distance at which certain inner and outer relations can be brought into adjustment; and that, other things equal, there is a simultaneous advance in the degree of life.
§ 136. Whatever may be the explanation of the fact, it is beyond question that in zoophytes the entire tissue has the property of responding to marked changes in the quantity of the light falling upon it; and that thus there is a foreshadowing of the visual faculty, and a vague indication of certain consequent correspondences, before yet there is any visual organ. This power of discerning the difference between light and darkness, does not produce anything like what we call sight, until it comes to be concentrated in a particular spot. The rudimentary eye, consisting, as in the Planaria, of a few pigment grains beneath the integument, may be considered as simply a part of the surface more irritable by light than the rest. We may form some idea of the impression it is probably fitted to receive, by turning our closed eyes towards the light, and passing the hand backwards and forwards before them. Manifestly, however, as soon as even this slight specialization of function exists, it becomes possible for the organism to respond to the motion of opaque bodies that pass near. While yet there is nothing but a general sensitiveness to light, the intercepting of the sun's rays by a cloud, an observer's hand, or anything which throws the whole or a greater part of the creature into shade, is required to produce an internal change; but when there comes to be a specially sensitive part, anything which casts a shadow upon that part alone, can cause an internal change. And as that which shades the light from only a small part of the organism, will usually be a comparatively small object; it follows, that this advance from the general sensitiveness of the whole organism, to the special sensitiveness of one portion of it, enables the organism to respond, not only to the most marked general changes in luminousness which its environment undergoes, but also to those most marked special changes in luminousness caused by the motion of bodies in immediate proximity.
The contrast between light and darkness, or more strictly, between widely different degrees of obscuration, being all that the most rudimentary vision recognizes; and any very distinct obscuration produced by an adjacent small body, requiring that it shall be extremely close; we may reasonably infer that nascent vision extends only to those objects which are just about to touch the organism, either in consequence of their motion or of its motion. We may infer that it amounts, at first, to little more than anticipatory touch; and that so there is established in the organism a relation between visual and tactual impressions, corresponding to the general relation between opacity and solidity in the environment. Be this as it may, however, it is clear that as soon as there comes to be a faculty of sight, though the vaguest imaginable in the sensations it gives, and the most limited that can be conceived in range, there is not only some extension of the correspondence in space, but a new order of correspondence makes its appearance.
It scarcely needs to say, that gradually as we ascend to creatures endowed with more complete visual organs, we find a gradual increase in the sphere of surrounding space through which external relations can establish corresponding internal relations. The first improvement, which apparently consists of nothing more than a slight convexity of the skin lying over the sensitive tract, must manifestly, by concentrating the rays, render appreciable, less marked variations in the quantity of light; and this must alike render perceptible the same bodies at a greater distance, and smaller or less opaque bodies at the same distance. From this point upwards, through the various families of mollusca, articulata, and vertebrata, inhabiting the water, and still more on passing to the rarer medium in which the highest creatures exist; we trace, under various forms and modifications, a more complex visual apparatus and a generally increasing distance through which the correspondence extends. It is needless to go into details. All hypotheses and illustrations aside, it is obvious that from the polype which does not stir till touched, up to the far-sighted vulture or the telescopic-eyed Bushman; one aspect under which progressing life shows itself, is the greater and greater remoteness at which visible relations in the environment can produce adapted relations in the organism.
§ 137. Similarly with the faculty of hearing. So long as the power of responding to sonorous vibrations is slight, and possessed by the body at large, there can be no response to those moderate and localized vibrations the appreciation of which constitutes what we commonly understand as hearing. Only when the susceptibility comes to be intensified in one place, can there be any appreciation of a sound proceeding from a particular point in the environment, as distinguished from the mere tremor of the environment as a whole. When there exists the rudimentary ear, consisting of a dermal sac containing otolithes, which have the function of concentrating the vibrations striking the skin that covers them, as the primitive cornea concentrates the rays passing through it; then, it is obvious, that a moderate sound occurring in close proximity to this sac, may produce on the organism as great an effect as the violent shock of its entire medium produces on an organism not thus endowed. And when a dawning sense of hearing arises, there comes into existence a new set of correspondences between certain auditory impressions and consequent motions in the organism, and certain sound-causing powers and coexistent properties in adjacent bodies.
As in the previous cases, the successive improvements in this faculty are seen in the expanding sphere of space throughout which a certain order of relations in the environment cause adapted relations in the organism. Passing over details, which indeed existing knowledge scarcely suffices to supply, it cannot be denied that though the minor irregularities involved by their special habits and discipline are considerable, yet, viewed in the mass, animals of higher and higher types exhibit a greater and greater range in their auditory correspondences.
§ 138. This continual widening of the surrounding space through which the correspondence between inner and outer relations extends, does not end with the perfecting of the senses. In creatures of comparatively advanced organization, there arise powers of adjusting the actions of the organism to coexistences and sequences in the environment that are far too remote for direct perception. No matter what the special mode in which it is achieved, it is clear that the process by which a carrier pigeon finds its way home, though taken a hundred miles away, is a process that cannot be effected by sight, smell, or hearing, in their direct and simple forms. Chased animals that make their way across the country to places of refuge that are out of immediate view, obviously do this by means of some combination of past and present impressions—a means which enables them to transcend the sphere of the senses. And thus also it must be with creatures that undertake annual migrations.
In man, this secondary process of extension becomes still more marked. Though, in respect to the correspondences effected by immediate perception, his range in space is narrower than that of some creatures of greatly inferior endowments; and though, in respect to that species of indirect adjustment of the organism to remote coexistences in its environment, just exemplified, he is inferior to sundry wild and domestic animals; yet, by the use of still more indirect means, he adjusts internal relations to external relations that are immensely more distant than those cognized by lower beings. By the combination of his own perceptions with the perceptions of others, as registered in maps, he can reach a special place lying thousands of miles away over the surface of the earth; and not only one such place, but endless such places. A ship, guided by compass, and stars, and chronometer, brings him from the other side of the Atlantic, information by which his purchases here are adapted to the prices there. An examination of the surface strata, from which he infers the presence of coal below, enables him to bring his actions into correspondence with the coexistences a thousand feet underneath. Nor is the range of environment through which his correspondences reach, confined to the surface and the substance of the earth. It stretches into the surrounding sphere of infinity. It was extended to the moon when the Chaldeans discovered how to predict eclipses; to the sun and nearer planets when the Copernican system was established; to the remoter planets when an improved telescope disclosed one, and calculation fixed the position of the other; to the stars when their parallax and proper motion were measured; and, in a vague way, even to the nebulæ, when their composition and forms of structure were ascertained.
§ 139. Before leaving this general proposition, that the progress of life and intelligence, is, under one of its aspects, an extension of the space through which the correspondence between the organism and its environment reaches, it may be needful to remark, that its truth is entirely independent of all conclusions as to the modes in which the correspondence is affected. With a view of indicating the probable continuity of the higher vital actions with those lower ones in which life commences, I have, in the earlier part of the chapter, filled up some of the gaps in our positive knowledge by reasonings that are more or less hypothetical; and by so doing, have opened the door to possible criticisms, which may at first sight be supposed to tell against the doctrine at large. But it needs only a moment's consideration to show, that by whatever steps the senses of smell, sight, and hearing, take their rise, the result remains the same. It is beyond question that in the lower types of animal life, where yet the sense of touch is the only one definitely manifested, the correspondence between the organism and its environment, extends only to that part of the environment by which the organism is actually bathed. It is beyond question that the appearance of the higher senses, even in their most rudimentary forms, is accompanied by some extension of the surrounding space throughout which correspondences can be effected. It is beyond question that the successive stages in the development of each of these senses, more or less regularly involve successive enlargements of this sphere of space. And it is beyond question that the advent of rationality, is, among other ways, shown in the carrying of these enlargements still further.
Here indeed, it may be well specifically to point out, what is obviously suggested by some of the facts cited above, that the extension of the correspondence in space, is exhibited, not only in the ascending grades of animal life, but in the successive phases of human civilization; and that it is even now going on. From the early races acquainted only with neighbouring localities, up to the modern geographer who can calculate the distance and direction of any point on the globe—from the ancient builders and metallurgists, knowing only surface-deposits, up to the geologist of our day, whose data in some cases enable him to describe the material existing at a depth never yet reached by the miner—from the savage barely able to say in how many days a full moon would return, up to the astronomer who ascertains the period of revolution of a double star—there has been a gradual widening of the range of environment throughout which the adjustment of inner to outer relations extends. And the fact that this is one of the aspects under which human progress has displayed itself, cannot fail to bring home with increased vividness the larger fact, that it is one of the aspects of vital progress in general.
It only remains to advert to the illustration thus afforded of the general truth, that the degree of life varies as the degree of correspondence. On the one hand, it is obvious that each new increment of space through which the correspondence extends, adds to the number of external relations to which internal relations are adjusted—adds, that is, to the number of internal changes—adds therefore to the amount of life. On the other hand, it is obvious that the greater the space throughout which the correspondence extends, and the greater the number of correspondences which can consequently be effected, the greater must be the number of cases in which food can be obtained and danger shunned, and the greater the ability to maintain life. Whence we may clearly see, how life and ability to maintain life, are two sides of the same fact—how life is a combination of processes the result of whose workings is their own continuance. A glance at the obverse of the proposition will serve still further to enforce it. For if, starting from the forms of life treated of in the last chapter, whose correspondences do not extend beyond the phenomena occurring in contact with their own surfaces, we ask under what form a greater correspondence between the organism and its environment must show itself; we at once see that it must show itself in adjustments to relations that do not occur in contact with the organism; that correspondences having been established to the few relations occurring in juxtaposition with the organism, the number of correspondences cannot be increased without beginning to take in relations that do not occur in juxtaposition with it; that with more or less regularity this must remain true of subsequent additions to the number of correspondences; and that thus the growth of a correspondence between the organism and its environment, necessarily involves a gradual extension of the correspondence in space.
THE CORRESPONDENCE AS EXTENDING IN TIME.
§ 140. It was pointed out some pages back (§ 130), that while, in those humblest protophyta and protozoa in which the cell-wall is continuously bathed with all the needful elements, there is no manifest adjustment of internal changes to changes in the environment, the higher plants pass through cycles of states in correspondence with the cycles of the seasons. Whether this should be regarded as a progress towards correspondence in Time, is somewhat doubtful. On the one hand, it may be said, that as, in a tree, the periods of budding, blossoming, ripening the fruit, and dropping the leaves, are adapted to successive external conditions, the inner sequences are conformed to the outer ones. On the other hand, it may be argued that this is but an incidental result of the perpetual adaptation of the internal actions to external coexistences (temperature, light, moisture), which, by passing through a series of variations, involve a parallel series of variations in the plant. It may be argued that the putting forth of leaves has reference simply to the then existing concurrence of certain environing influences, and has no direct reference to the subsequent nutrition of the fruit; that a succession of environing influences produce a succession of adjusted processes in the plant, and that the production of fruit is simply a cumulative result of these; that the true nature of these vegetative changes is seen in the fact, that a tree will blossom in the autumn if the temperature be sufficiently high; and that thus, plant life exhibits no true correspondence to sequences in the environment, but only to coexistences in it. Definitely to decide between these views is not easy; though on the whole the last one seems the more philosophical. But at any rate, this species of correspondence in Time, if such it be, is of an indirect and vague kind compared with that properly so called.
Setting aside this debateable case of the constitutional changes which all organisms undergo in response to the seasons, and turning to those more definite cases which animal life in particular displays; it is to be observed that in creatures not endowed with sensibility, as well as in those possessing no other sense than that of touch, the sole external relations with which internal relations can be put in correspondence, are relations of coexistence. It is only when there comes to be some amount of smell, sight, or hearing, that sequences in the environment can be met by adjusted sequences in the organism. The relation between the tangibility of an adjacent body, and some coexistent property possessed by it, is the only one to which, in a zoophyte, the organic relation between irritation and contraction answers. Time is no more involved in the correspondence than Space. But when relations among things or attributes that are in any degree removed from the organism, become cognizable—when, for example, there exists incipient vision, and obstruction of light is habitually followed by a touch from the obstructing body; then, an organic response to an external relation of sequence becomes possible; then, it becomes competent to the organism to move in anticipation of motion in an external body. Two phenomena in the environment, the one immediately succeeding the other, can produce two phenomena in the organism in like succession. And thus, an extension of the correspondence in Time, begins simultaneously with its extension in Space.
Or to present the proposition under another aspect:—As the simplest sequences, and those first cognized, are mechanical sequences; as mechanical sequences involve change of position; as change of position involves progress through Space; it follows, that only when there comes to be some degree of space-penetrating faculty, can there be any adaptation in the organism to changes of position in adjacent objects—any adjustment to external sequences—any correspondence in Time. After the ability to respond to the touch of surrounding bodies, the next advance is the ability to respond to that motion of them which precedes touch; and as motion involves both Time and Space, the first extension of the correspondence in Time is necessarily coeval with its first extension in Space.
§ 141. Throughout the successive stages in the development of the perceptions, these two orders of correspondence must progress together with more or less regularity. In proportion as the distance at which a moving object is cognizable, increases, the greater becomes the duration of the external sequence, or chain of sequences, to which the internal actions may be adjusted. Other things equal, the more remote any body in the environment, the longer must be the period before it can act on the organism or the organism on it; that is—the more extended must be the time between those outer antecedents and consequents with which the inner antecedents and consequents are put in correspondence. The inner and outer sequences exhibited in the pursuit of a heron by a hawk, are longer than those exhibited in the pursuit of a fish by a heron; and are so chiefly because the vision of a heron is more extensive than that of a fish. And without giving cases, it will be manifest, that by smell and hearing also, in proportion as they are acute, the correspondences are simultaneously extended in duration and distance. Not that there is a constant ratio between these forms of advancing correspondence. The connection between them is variously modified by circumstances. The special character of the environment, the particular powers of the organism in respect of locomotion, as well as other conditions, greatly affect it. All that can be established, is, that the two kinds of extension are connate; and that, in so far as mechanical phenomena are concerned, they display throughout a general interdependence.
§ 142. This limitation—“in so far as mechanical phenomena are concerned”—serves to introduce the fact, that, in respect to other orders of phenomena, the progress of the correspondence in Time, has little or nothing to do with its progress in Space. Did all changes involve perceptible motion—were alteration of position a necessary accompaniment of every alteration, the two would be uniformly related. But as there are hosts of changes, chemical, thermal, electric, vital, which involve no appreciable mechanical change—as there are numberless changes of state which occur without change of place; it results, that in the growth of internal adjustments to these, there is an extension of the correspondence in Time, separate from, and additional to, that which arises from its extension in Space.
This species of correspondence in Time, is of a much higher order than that which is displayed in respect to most mechanical sequences—is in fact a far more extended correspondence. For the greater part of those mechanical sequences in surrounding bodies, by which any organism is affected, are incalculably more rapid than the non-mechanical sequences occurring in them. The motions of enemies or of prey, even when sluggish, are readily appreciable: a few seconds only, at most, is needed to bring about a manifest change. But the decay of a dead animal, the ripening of fruit, the drying-up of a pool, the hatching of an egg, require periods incomparably longer. Sequences of the latter order occupy a hundred, a thousand, a million times the periods required for those of the former; and the ability of the organism to adjust itself to them, implies a proportionably great extension of the correspondence in Time.
Hence the fact, that throughout all the lower orders of creation, it is only to coexistences and mechanical sequences in the environment that the actions of the organism respond. Hence the fact, that it is only when we come to creatures of a comparatively high degree of intelligence, that we meet with any inner changes in adaptation to outer changes of a non-mechanical kind. For we must not class as coming under this secondary species of correspondence in Time, those acts of the inferior animals which are adjusted to the daily and annual modifications of the environment. These, like the parallel phenomena seen in plants, are most likely nothing but the cumulative results of successive adaptations of the organism to successive coexistences in the environment. It is anatomically demonstrable, that the pairing and nidification of birds in the spring, is preceded by constitutional changes, in all probability produced by more food and higher temperature. And it is a rational inference, that the whole series of processes implied in the rearing of a brood, are severally gone through, not with any recognition of consequences, but solely under the stimulus of the conditions immediately present from hour to hour, and day to day.
The earliest examples of the higher kind of correspondence in Time, must be looked for in cases where the period between antecedent and consequent is but a few hours. Birds that fly from inland to the sea-side to feed when the tide is out, and cattle that return to the farmyard at milking-time, supply instances. Even in these cases, however, it must be observed, that there is not a purely intelligent adjustment of the inner to the outer sequences; for creatures long accustomed to eat or be milked at definite intervals, necessarily come to have an adapted recurrence of constitutional states, and it is the sensations accompanying these states, which form the proximate stimuli to their acts. Nevertheless, we must not wholly exclude these instances from the category of advancing correspondence in Time: but must recognize them as imperfect and transitional forms of it, through which only the higher forms can be reached. For if we consider under what conditions only, a sequence in the organism can be adjusted to some lengthened sequence in the environment—some sequence occupying hours or days—it becomes manifest that there must exist in the organism, a means of recognizing duration. Unless the organism is capable of being differently affected by periods of different lengths, its actions cannot be made to fit slow external actions. Now, when we pass from those mechanical sequences in which the motion of the external body itself serves the organism as a measure of duration, to those non-mechanical sequences which not only afford no measure, but last incomparably longer, it is obvious that the only measure of duration available, must be that arising from the periodic sensations of the organism itself. Hence the fact, that these first examples of the higher order of correspondences in Time, are examples in which an internal periodicity agrees with an external periodicity. And hence the fact, that in the cases next above these—cases showing some foresight of future events, such as is exhibited by a dog hiding a bone in anticipation of the time when he will be again hungry—there is a distinct reference to this same recurrence of organic states.
§ 143. The circumstance that there is so wide a gap between ordinary mechanical sequences and most non-mechanical sequences, in respect of the periods they occupy; joined with the circumstance that to effect a correspondence between internal sequences and lengthened external sequences, implies some mode of estimating time; serve at once to explain how it happens, that only when we reach an advanced phase of intelligence, does this higher species of correspondence in Time begin to exhibit a marked extension. It is not until we arrive at the human race that the slow vital, chemical, thermal changes undergone by objects in the environment, are met by adapted changes in the organism. Not that the transition is sudden. There is evidence that in the first stages of human progress, the method of estimating epochs does not differ in nature from that employed by the more intelligent animals. There are still historical traces of the fact, that originally, mankind adjusted their actions to the longer sequences in the environment, just as Australians and Bushmen do now, by observing their coincidence with the migrations of birds, the floodings of rivers, the flowerings of plants. And it is obvious that the savages, who, after the ripening of a certain berry, travel to the sea-shore, knowing that they will then find a particular shell-fish in season, are guided by much the same process as the dog, who, when he sees the cloth laid for dinner goes to the window to watch for his master. But when it comes to be noticed that these phenomena of the seasons coincide with recurring phenomena in the heavens—when, as was the case with the aboriginal Hottentots, periods come to be recognized partly by astronomical, and partly by terrestrial changes; then, for the first time, we see making its appearance, a means whereby the correspondence in Time may be indefinitely extended. The periodicity of the sun's daily movements, and the monthly phases of the moon, having once been observed; and some small power of counting having been reached; it suddenly becomes possible to recognize the intervals between antecedents and consequents that are long apart, and to adjust the actions to them. Multitudes of external sequences whose lengths do not agree with those internal cycles produced by alternating light and darkness, nor with those that result in recurring appetites, and which, from having no organic periods answering to them, cannot be responded to by the organism, may be discerned and conformed to when there arises this ability of numbering days and lunations. Given a unit of Time, and a faculty of registering the units, and it becomes possible for the internal actions to be adjusted to those endless non-mechanical actions going on externally, which, though the least conspicuous, are often the most potent in their effects on the organism.
This higher order of correspondence in Time, which, for the reasons assigned, is impossible to creatures of inferior type; which is but vaguely discernible in the higher animals; and which is definitely exhibited only when we arrive at the human race; has made marked progress in the course of civilization. Among the lowest tribes of men, who are without habitations, and who wander from place to place as the varying supplies of wild animals, roots, and insects, dictate, a year is the longest period to which the conduct is adapted. Hardly yet worthy to be defined as creatures “looking before and after,” they show by their utter improvidence and their apparent incapacity to realize future consequences, that it is only to the conspicuous and often-recurring phenomena of the seasons, that their actions respond. But in the succeeding stages of progress, we see, in the building of huts, the breeding and accumulation of cattle, and the storing of commodities, that longer sequences are recognized and measures taken to meet them. And gradually as we advance to higher social states, men show, by planting trees that will not bear fruit for a generation; by the elaborate educations they give their children; by building houses that will last for centuries; by insuring their lives; by all those strugglings for future wealth or fame, which now mainly occupy the educated classes; that in them, internal antecedents and consequents are habitually adjusted to external ones that are extremely long in their intervals. More especially, however, is this extension of the correspondence in Time, displayed in the progress of science. Beginning with a recognition of the sequences of day and night, men next advanced to those monthly ones exhibited by the moon; next to the sun's annual cycle; next to the cycle of the moon's eclipses; afterwards to the periods of the superior planets; while modern astronomy determines the vast interval after which the earth's axis will again point to the same place in the heavens; and the scarcely conceivable epoch in which planetary perturbations repeat themselves.
And here it is to be remarked that in the case of these slow sequences, whose durations exceed in length the lives of individual men, the correspondence is effected by the agency of many men whose actions are co-ordinated. The astronomer who calculates the orbit of a comet of brief period, and who, after the lapse of certain years, months, and days, turns his telescope to that region of the heavens in which the expected body shortly makes its appearance, exhibits in himself, the entire correspondence between an internal series of changes and an external one. But where centuries intervene between the prediction and the fulfilment, we see that by the help of language, the proceedings of several successive men are united into one long sequence, displaying the same adjustment to an external sequence as though it had occurred in a single individual living throughout the whole interval. Perhaps nothing tends so strongly to suggest the conception of an embodied Humanity, as this fact that Humanity in general, can respond to environing changes which are far too slow to be responded to by its component individuals.
§ 144. The extension of the correspondence in Time, like its extension in Space, both involves an increase in the amount of life, and renders possible a greater continuity of life. Each advance in the recognition of more and more elongated sequences, is an adjustment of a new set of internal relations to a new set of external relations—implies an additional series of vital actions—implies therefore an increase in the number and heterogeneity of the combined changes which constitute life. And at the same time, the adjustment of the organism to these successively longer sequences, is itself an avoidance of those dangers, or a seizing of those advantages, which such longer sequences present; and is consequently a process of self-preservation. Not only, as we have seen, do the ascending grades of brute life illustrate this; but it is illustrated by human progression. All the above instanced cases in which the more civilized races recognize slower changes, and provide for more remote results, than the comparatively hand-to-mouth-living savage does, are obviously cases in which a greater number of contingencies are met, and a greater duration of life secured: while, in the meeting of this greater number of contingencies, a higher degree of vital activity is necessarily displayed. And it may even be argued with some plausibility, that the like is true, not only with respect to those shorter processes of causation which science discloses to us, but with respect also to the scarcely conceivable periods involved in the larger generalizations of astronomy and geology. For little as the recognition of these modifies human actions directly; yet indirectly, by throwing light upon the history and nature of the universe, and so influencing men's theories of creation and humanity, it ultimately produces a powerful effect upon the conduct of the race.
THE CORRESPONDENCE AS INCREASING IN SPECIALITY.
§ 145. From another point of view, the evolution of life is an advance in the Speciality of the correspondence between internal and external relations. In part, this is another aspect of the processes delineated in the last two chapters; and in part, it is a further and a higher process. Just as we saw that in so far as mechanical phenomena are concerned, the extension of the correspondence goes on pari passu in Space and in Time, but that the extension of the correspondence in Time, afterwards takes in many other orders of phenomena; so, though at first the increase of the correspondence in Speciality is inseparable from its extension in Space and Time, yet it presently comes to include innumerable correspondences not comprehended under either of these. Objectively, the entire development of the correspondence is essentially one: the limitations of our intellects prevent us from grasping it as one: and it is an inconvenience accompanying the presentation of it in parts, that the divisions more or less overlap each other.
The first step in the specialization of the correspondence is seen on passing from those simplest of all organisms whose environments are homogeneous both in Space and Time, to those whose environments, though homogeneous in Space, are heterogeneous in Time. It is clear that the yeast-cell, touched on all sides by the elements required for its vital actions, and, during its short life, continuously supplied with them under the needful conditions, exhibits a correspondence in the highest degree general. And it is clear that the tree, which, though constantly bathed with nutritive materials, assimilates them only under particular states of the environment, exhibits, in the adjustment of its internal changes to the recurring external changes, an advance towards speciality of correspondence.
The next step of the same nature—the step which distinguishes, so far as it can be distinguished, the animal kingdom from the vegetable one—takes place when, relatively to the needs of the organism, the environment is heterogeneous both in Time and Space. Generally speaking, we may say that while, to the lowest forms of life, the integrable matter is everywhere present under uniformly available conditions; while, to plants, it is everywhere present, but not under uniformly available conditions; to animals, it is neither uniformly present nor present under uniformly available conditions—it exists in particular bodies irregularly dispersed through the environment, which are to be obtained only by particular actions. And thus, change from a general diffusion of nutriment to a specialization of it, involves a further specialization of the correspondences. Unable to grow by mere passive absorption of surrounding elements, the condition under which alone the organism lives, is, that contact with special masses of matter shall be followed by the special acts required to utilize them. Even while yet there are neither prehensile nor digestive organs, we see, in the Amœba, which wraps itself round, and gradually includes, the small bodies it meets with, how necessary is the connection between this new set of external relations and a new set of internal ones. We see how the existence of its food in a solid form, necessarily implies that the organism shall respond differently to the contacts of solid matter and of fluid matter; and how this is a progress towards speciality of correspondence.
And when there arises the primary division of the tissue into stomach and skin—when the established differentiation in the environment, is met by an established differentiation in the organism—when to the ability to distinguish solid from fluid matter, comes to be added the ability to distinguish different orders of solid matter from each other, we see, dimly shadowed forth, those many successive specializations which accompany the development of the senses. These we have now to consider.
§ 146. Out of the primordial irritability, which (excluding the indeterminate types of life that underlie both divisions of the organic world) characterizes animal organisms in general; and in virtue of which arises the response produced by the contact of solid bodies, as distinguished from the fluid medium; are gradually evolved those various modified kinds of irritability, answering to the various attributes of matter. The fundamental attribute of matter is resistance. The fundamental sense shows itself as a faculty of responding to resistance. And while, in the environment, associated with this attribute of resistance, are sundry other attributes severally distinctive of certain classes of bodies; in the organism, there successively arise faculties of responding to these other attributes—faculties, that is, which enable the organism to adjust its internal relations to a greater variety of external relations—faculties, therefore, which increase the speciality of the correspondence.
This is seen not only in the gradual process of differentiation by which the fundamental irritability gives origin to the senses that recognize the sapid, odorous, visible, and sound-producing properties of things; but it is seen in the series of phases through which each sense advances to perfection. For every higher phase shows itself as an ability to recognize smaller and smaller differences, either of kind or degree, in the attributes of surrounding bodies; and so renders it possible still further to specialize the adjustment of inner to outer relations.
In the case of touch, an advance is early shown in the power to distinguish a large moving mass from a small one, by the force of its collision. This is seen even in the zoophytes, which contract bodily if their tentacles are roughly handled, but draw in particular tentacles only if these are touched lightly. When, as in higher grades of creatures, a muscular system and a concomitant muscular sense are developed, there arises an appreciation of relative degrees of hardness in the objects met with; as is proved by the differences between the actions which follow the contact with soft and hard bodies respectively. Afterwards textures become cognizable, and also amounts of tenacity; as illustrated in the act of a spider testing the strength of its web. Finally, when there come to be complicated prehensile organs, the sizes and shapes of the things laid hold of are perceived; and the conduct modified accordingly. And when all these subdivisions of the faculty of touch are fully developed, as in the human being, we find that between the extremes of hardness and softness a great number of gradations can be appreciated; that an immense variety of textures can be known tactually; and that endless objects can be identified by their differences of size and shape, ascertained by the fingers only.
That special kind of touch which we call taste, and which may be generally, though not accurately, described, as a sense serving to distinguish matters that are soluble from those that are insoluble, presents us with a series of gradations of like kind. Regarding only the lower families of creatures, which, if not without exception aquatic, are in all cases surrounded by a fluid of which water is the chief constituent, it is obvious that, to them, the insoluble bodies are one with the inorganic bodies, and that the soluble more or less completely answer to the organic. In the sea, or a river, matter which permanently continues undissolved, is stone or earth; while matter which, though soluble, is found in a solid form, is something alive. Hence, to those lowest creatures, which feed on any organic substance, the soluble and the insoluble,—the things that have taste, and the things that are tasteless,—stand respectively for food and not-food. From this stage upwards, successive specializations, of which we may presume the first to be in an ability to distinguish organic matter into animal and vegetable, display themselves in the narrowing of the classes of things which are eaten. Fish that take particular baits, insects and quadrupeds that feed on particular plants, illustrate this. Obviously, it is neither needful nor practicable to trace out this progress in detail. It suffices to notice that the higher animals exhibit a power of perceiving an increased number of gustable differences; and that when we reach man, we find the faculty so far developed that it enables him not only to identify a great variety of edible substances, but serves the chemist and the mineralogist in classifying those inorganic compounds which are in any degree soluble.
Smell, which, as before suggested (§ 134), has probably a common origin with touch and taste in the fundamental process of assimilation, and is to all appearance gradually differentiated from these, passes through parallel stages of development. At first, merely, as we may presume, a kind of anticipatory taste, and in common with taste employed to distinguish nutritive from innutritive matters, it more or less manifestly progresses in speciality in proportion as the food is specialized; or to put the facts in logical order:—the ability to select special food, is in most cases dependent on the minuteness of the differences which the smelling faculty can appreciate. Not that this is so throughout; for prey is in many cases recognized by other means than scent: but it is so with most insects and plant-eating quadrupeds; and with a considerable proportion of creatures that are carnivorous. These gradations in the olfactory sense, which are most clearly displayed in the mammalia, reach in some of those that hunt by scent, to a high degree of perfection. Not only do we see in such, an ability to identify the species of creature pursued; but the dog, which, with nose to the ground, traces out his master, shows us that he can not only distinguish by scent one class of bodies from all other classes, but can even distinguish a particular individual belonging to that class, from all the other individuals it contains.
The increasing speciality of the correspondences effected by means of vision, in its ascending stages of development, is still more conspicuous. The lowest form of vision appears to be nothing further than a sensitiveness to the proximity of a body which intercepts the light. Marked differences in the quantity of light, and such surrounding changes as cause these differences, are alone responded to. Presently, when less marked differences become appreciable, and when the sensitive tract on which the rays of light are concentrated, is such that a part of it can be stimulated without the stimulation of the whole; there arises an ability to distinguish adjacent objects by their power to reflect light, as well as by their power to intercept it. The differences in light-reflecting power possessed by white and black bodies having become appreciable, we may presume that a further progress of like nature renders perceptible smaller and smaller gradations in the transition from whiteness to blackness; and so adds to the number of things that can be discriminated. Then to increasing ability to recognize differences in the quantity of light, has to be added an ability to recognize differences in its quality; which, in all probability, arises simultaneously. Things that are red, yellow, and blue, come to be differentiated from each other in their effects on the organism; as well as those that are white and black. And familiar facts clearly show, that in the evolution of the visual faculty, the progress is towards a capacity to discriminate a greater variety of intensities of colour, of intermediate tints, and of degrees of light and shade. Gradually too, as there is developed a more expanded retina, and as, consequently, any marked differences in the areas occupied by images cast upon it become appreciable, there arises a possibility of distinguishing differences of bulk in adjacent objects. The approach of a large body changes the state of a greater portion of the retina than the approach of a small one; whence results an appropriate difference of action. And as in the case of amounts of light and qualities of colour, the successive advances result in the perception of smaller and smaller distinctions. Finally, there is reached the ability to recognize not only size but shape. A further specialization of the sensitive tract—a minuter division of it into separate nervous elements, renders it a fit instrument for this. Employed by an organism of proportionate complexity, an eye of advanced structure gives different impressions, not only according to the number of its component nerve fibres that are simultaneously affected, but according to the particular combinations of them that are simultaneously affected: and the particular combinations, varying as they do with the forms of the bodies seen, serve as stimuli to the appropriately varied actions. All which several kinds of visual development displayed throughout the animal kingdom, end in giving to man the power to identify by the eye an infinity of different objects; and so to make an infinity of particular adaptations in his conduct.
Similarly with hearing. In its lowest form, nothing but a sensitiveness to violent concussions affecting the whole environment, this sense, when localized and developed, becomes a means of distinguishing differences in the strengths of the vibrations; that is—the loudness of the sounds. A moderate sound near to the aural organ, produces a different effect on the organism from one causing a distinct tremor of the whole surrounding fluid; and step by step, as the multiplying apparatus of which the ear essentially consists, exhibits a more perfect construction, a greater number of degrees of intensity become perceptible: as is illustrated by animals which listen, or pursue, or seek refuge, according as some neighbouring noise is faint, or moderate, or startling. Higher endowments of the faculty are further accompanied by increasing ability to discriminate qualities as well as quantities of sound. Birds which answer each other in the woods—birds whose songs are made up of intervals more or less truly answering to musical ones, and which may be taught definite melodies, must obviously be able to recognize a great number of differences in pitch. Parrots, whose range of imitations not only exhibits great compass in pitch, but great variety in timbre, show a power to appreciate that secondary order of qualities by which tones of the same pitch are distinguished from each other. By most domestic quadrupeds, and especially such as answer to their names, marked contrasts of pitch or timbre, or of both, are responded to. And among men, or more strictly speaking, among civilized men, the aural faculty reaches a development which, besides enabling them to recognize numerous adjacent creatures, various mechanical operations, countless natural phenomena, by the sounds that accompany them, further enables them to identify unseen persons by the loudness, pitch, and timbre of their voices, and even to perceive the particular states of feeling in which such persons then are.
Thus, throughout the whole animal kingdom, the specialization of the senses is a measure of the specialization of the correspondences between inner and outer relations—is nothing but a means to such specialization. Not only in the differentiation of the senses from each other, but in the differentiation of each sense into those several divisions which eventually constitute it, and in the differentiation of each of these divisions into the minute subdivisions which render possible the appreciation of minute distinctions, we see a series of subjective modifications fitting the organism to respond to a greater and greater number of those objective modifications which characterize the things in its environment.
§ 147. But the increase of the correspondence in speciality, by no means ends with the development of the senses. Nor is it adequately represented, even among the lower animals, by a description of this development. For, during the same time that the advancing faculties of touch, taste, smell, sight, and hearing, have rendered it possible for the organism to respond to smaller differences in the simpler properties of things, there has been growing up a power of responding to those higher properties of things that are not cognizable by direct sensation. This makes its appearance so gradually, and is so intimately associated with the simpler functions of the senses, that it is scarcely possible to treat of the one without in some degree involving the other. Indeed, in the foregoing section, the boundary line has been crossed, alike in speaking of visible and of tangible form, and, to a smaller extent, in other cases.
What is the essential nature of this higher order of specialized correspondences, it will be more convenient to consider hereafter under another head. For the present, it will suffice to say, that they are seen wherever Space or Time, or both Space and Time, are involved. Let us look at the matter in the concrete.
First it is to be observed, that in themselves, the extensions of the correspondence in Space and in Time, both imply increased speciality of correspondence; differing in kind from that above described, though inseparable from it in origin. A higher development of the eye, gives simultaneously a greater ability to identify distant objects, and a greater ability to discriminate between the relative sizes of near objects. And it is manifest that these connate abilities to identify objects at a distance, and to appreciate differences of apparent magnitude, give together a power of estimating distance: whence must arise differences of action, according as the perceived enemies or prey, are dangerously near or hopelessly remote; and these differences of action imply a new series of special correspondences. Manifestly, also, the extension of the correspondence in Time, involves analogous results: seeing that when, instead of responding only to those brief mechanical sequences which occur close to it, the organism possesses an ability to recognize mechanical sequences of longer duration, and afterwards non-mechanical sequences; and when, as a consequence, instead of meeting all these sequences by some one defensive action, as retreat into its shell, it becomes possible for it to meet them by different actions, according to their lengths; the correspondences must become, by implication, more and more special
This being understood, it will at once be seen that when that speciality of correspondence which exhibits itself in the discrimination of objects from each other, is united with that speciality of correspondence which exhibits itself in the discrimination of distances in Space or Time, there arises a new and a higher order of special correspondences; or more correctly—the previously specialized correspondences are still further specialized. And when, as during this same progress, there is developed a power of recognizing direction in space, the speciality is again increased. To another set of distinctions in the environment, there is another set of adjustments in the organism. These general truths will be best elucidated by a few illustrations.
Among the lower aquatic creatures endowed with some degree of activity, and with vision extending to a few feet, may be observed cases in which the approach of any large object, is responded to simply by a series of convulsive movements, which may end in removing the creature to a greater distance from the approaching body, or in bringing it nearer, or in leaving it nearly where it was. The random leaps which a flea makes in its attempts to escape, are of like nature; showing, as they do, no recognition of the whereabouts of the pursuer. On the other hand, the movements of a fish when alarmed, or of a fly when approached by the finger, are, like those of all higher creatures, away from the object to be escaped. The particular direction of something in the environment, is responded to by a particular adjustment in the motions of the organism—the correspondence is comparatively special. When, again, not only the direction but the nature of a neighbouring body can be perceived, by virtue of its colour, or the sound it makes, or both—as exemplified in the deer that gallops away from a creature that barks but not from one that bleats, in the bee that flies towards a flower, in the trout that rises at one object but not at another—there is a yet further specialization. And as not only colours and sounds and directions, but magnitudes and forms and distances come to be appreciated, there result all those more definitely adjusted actions by which the higher animals elude danger and secure prey—actions such as those of the chamois springing from crag to crag; of the hawk pouncing upon its quarry; of the dog catching the morsel of food thrown to it; of the bird building its nest and feeding its young.
In like manner, that increased speciality involved by extension of the correspondence in Time, when joined with that increased speciality resulting from a better discrimination of objects, gives origin to another series of higher specializations. There is a response to the sequences exhibited by particular classes of bodies; not simply to those exhibited by bodies in general. And manifestly, as fast as the number of sequences that can be distinguished from each other in length, accumulates; and as fast as there is a multiplication in the number of things distinguished from each other; so fast can there be an increase in the number of adjustments of the organism to the special actions going on in its environment. Save in respect to rapid mechanical changes, there are no correspondences of this order among the lower classes of creatures; and, lacking as they do the ability to estimate time, even the higher quadrupeds supply but few and imperfect examples of it. The lion that goes to the river side at dusk to lie in wait for the creatures which come to drink; and the house-dog standing outside the door in the expectation that some one will presently open it; may be cited as approximative instances. But only when we come to the human race, are correspondences of this degree of speciality exhibited with distinctness and frequency. In preparing his weapons against the approaching immigration of certain birds; in putting aside to dry, the skins which he preserves for clothing; in making the fire by which to cook his food; in various of his in-door and out-door actions; the savage adapts his conduct to the special changes undergone by special bodies during definite intervals.
Finally, we reach those still higher cases where there is speciality alike in space, time, and object—where the action of the organism is in correspondence with the changes of a particular thing in a particular spot at a particular period. A large proportion of human actions, even among the uncivilized, are of this nature. The going to certain places, at certain seasons, to gather certain natural productions then fit for use; the endeavour to intercept an animal that is making for a retreat, by getting there before it; these, and numerous daily procedures, exemplify this order of correspondences.
§ 148. Under this, as under previous aspects, an advance of the correspondence between the organism and its environment, is markedly displayed in the course of human progress. Not only is it that in the growth of classifications and nomenclatures we see the establishment of a greater number of distinctions among surrounding things, and a conforming of the conduct to their respective properties—not only is it that in the development of agriculture, the serial changes undergone by a variety of plants and animals have become known, and special materials, times, modes, places, adopted for the production of each—not only is it that the growth of the Arts has involved an incalculable multiplication of special processes adapted to produce special changes in special objects—not only is it that our whole social life, alike in the manufactory, in the shop, on the highway, in the kitchen, displays throughout, the performance of particular actions towards particular things in particular places at particular times; but it is that in what is commonly termed exact science, or rather in the actions that are guided by exact science, civilization presents us with a new and vast series of correspondences altogether transcending in speciality those that preceded them. For this that we call exact science, is in reality quantitative prevision; as distinguished from that qualitative prevision exhibited in ordinary knowledge. The progress of intelligence has gradually given the ability to say, not only that such and such things are related in coexistence or sequence; but that the relation between them involves such and such amounts of space, time, force, temperature, &c. &c. It has become possible to predict, not simply that under given conditions two things will always be found together; but to predict how much of the one will be found with so much of the other. It has become possible to predict, not simply that this phenomenon will occur after that; but to predict the exact period of time at the end of which it will occur, or the exact distance in space at which it will occur, or both. And manifestly, this reduction of phenomena to definite measure, gives to those proceedings of the organism that correspond with them, a degree of precision, a special fitness, far exceeding that possessed by ordinary ones. There is an immense contrast in this respect between the act of the astronomer, who, on a certain day, hour, and minute, adjusts his instrument to watch the commencement of an eclipse; and that of the farmer, who so arranges his work that he may have hands enough for reaping some time in August or September. The chemist, who calculates how many pounds and ounces of quick-lime it will require to decompose and precipitate all the bicarbonate of lime which the water in a given reservoir contains in a certain percentage, exhibits an adjustment of inner to outer relations incomparably more specific than does the washerwoman who softens a tub-full of hard water by a handful of soda. In the completeness of their adaptation to external coexistences and sequences, there is a wide difference between the proceedings of ancient besiegers whose battering rams were indeterminate in their action, and those of the scientific artillery-officer of our own day; who, by means of a specific quantity of powder, consisting of specific ingredients, in specific proportions, placed in a tube at a specific inclination, sends a bomb of specific weight, on to a specific object, and causes it to explode at a specific moment. Similarly with all the results of applied science; which not only gives greater speciality to previous correspondences, but renders possible hosts of correspondences before impossible. And when we bear in mind, not only that science, considered as the development of qualitative prevision into quantitative prevision, is thus distinguished by the relatively high speciality of the correspondences it achieves; but that, as contemplated in its own progress, it has been continually advancing in the precision of its results, alike in astronomy, physics, mechanics, chemistry—has been ever becoming more accurately quantitative, more special in its previsions; it becomes obvious, that even the most transcendent achievements of rationality are but the carrying still further that specialization of the correspondences between the organism and its environment, which is displayed in the evolution of Life in general.
§ 149. To follow the practice adopted in previous chapters, it may be as well here to point out, that this increase in the speciality of the correspondence, like its extension in Space and Time, is both in itself a higher life, and contributes to greater length of life. Inability to distinguish between surrounding bodies of different natures, must necessarily be attended by fatal errors in the conduct pursued towards them; while, conversely, the greater the power to recognize the multitudinous distinctions among such bodies, the greater must be the number of special adjustments that can be made to them, and the more complete must be the self-preservation. The proposition is in essence a truism. It is almost a truism, too, to say, that in proportion to the numerousness of the objects or classes of objects that can be separately identified—in proportion, that is, to the number of distinct attributes and combinations of attributes that can be cognized; and in proportion to the number of coexistences and sequences that can be severally responded to; must be the number, and rapidity, and heterogeneity, of the changes going on within the organism—must be the amount of vitality. Indeed, there is apparently no single formula which so well expresses the entire progress of Life, as this increase in the speciality of the correspondences between inner and outer relations. For, taking the extreme case, it is clear that did the actions of an organism accurately respond to all the coexistences and sequences of all things whatever in its environment, its life would be eternal. And it is equally clear that the infinity of internal changes involved in effecting the correspondence with an infinity of external relations, would imply the highest conceivable degree of vital activity.
THE CORRESPONDENCE AS INCREASING IN GENERALITY.
§ 150. That the adjustment of inner to outer relations progresses in generality at the same time that it progresses in speciality, will be thought a contradiction. It is however a purely verbal contradiction: the generalities being of quite different orders. The correspondences we meet with in the lower forms of life, are extremely general in the sense that those relations in the environment to which organic relations respond, are everywhere present, and continuously present. During a summer's day, light, heat, and carbonic acid, coexist in all portions of the space surrounding a plant; and the dependent chemical changes within the plant, go on simultaneously in all its leaves, for as many hours as the surrounding elements remain in the same relation. Hence, the correspondence, involving neither any special point in space nor any special moment in time, is of a very general nature. And the like is the case with those inferior types of animal life, to which the environment presents both the disintegrating and the integrable matter in a diffused form. The generalities, however, to which the organism responds more and more the higher it advances, are not those exhibited by the mass of the environing medium; but those exhibited by the individual objects contained in it: and generalities of this kind can become cognizable only as the intelligence is developed. The condition under which alone there can be established in the organism, general relations corresponding to the general relations displayed in common by several different groups of bodies, but not by other groups, is, that it shall have such experiences of various groups of bodies as shall enable it to distinguish among them. Only when there comes to be a multiplication of the classes of separate bodies that give it different experiences, can it possibly possess subjective generalities parallel to those objective generalities which bind together classes superficially unlike.
There are indeed generalities of a certain kind, which diminish in extensiveness as the specialities increase in number—generalities which form the raw material out of which specialities are produced by continual subdivision: the generalities, namely, in virtue of which surrounding objects are distinguished into classes. The growth of an ability displayed in successive orders of inferior organisms, to respond to the distinction between fluid and solid matter; then to the distinctions which respectively mark fluid, inorganic, and organic matters; afterwards to those of fluid, inorganic, vegetable, and animal matters; imply a correspondence to generalities that are step by step less comprehensive. And gradually as these classes become differentiated into smaller divisions, ending finally in species, they severally include fewer examples. These, however, are generalities, which, under their converse aspect, we have considered in the last chapter. For all special correspondences, with the exception of those highest ones which show themselves in the recognition of individual objects and acts, are really the manifestations of general correspondences covering certain groups of cases. The precautionary acts of a barn-door fowl on seeing a hawk hovering above, have no relation to that hawk in particular, but to the class of hawks in general. The correspondence is special, only in the sense of referring to the small class, hawks, instead of to the large class, birds. Even with respect to this order of generalities, however, it may be said, that as the formation of narrower and narrower ones does not involve the abolition of the wider ones which preceded them, but is merely an addition of secondary generalities to primary ones, there is an increase in the number of them, though not an increase in comprehensiveness.
But that advancing generality of correspondence which we have here to contemplate, is one which shows itself in the recognition of constant coexistences and sequences other than those which serve for the establishment of special classes—coexistences and sequences that are common to many classes apparently distinct; and which serve to reunite under fresh categories, things and changes that have come to be regarded as entirely unlike. Instead of being seen in a response to the constant relation between a particular scent, and the colour, size, form, actions, and cries, of the creature possessing it—a relation that is simple, and uniformly presented—it is seen in a response to some such relation as that between bulk and weight, or inanimateness and passivity—a relation which extends beyond class limits, and obtains under great dissimilarity of appearances. Obviously the growth of generalities of this order, must follow a course just the reverse of that followed in the growth of the preceding ones.
To trace up this growth from the lower to the higher forms of life, after the manner pursued in previous chapters, is extremely difficult, if not impossible. For it is in the very nature of this species of correspondence, that it does not manifest itself in any distinct, uncombined forms. The extensions of the correspondence in Space and Time, as well as its increase in Speciality, are experimentally demonstrable; but an internal relation that is parallel to some external relation which is more or less abstract—which is not peculiar to definite classes of things—which has no particular concrete embodiment—cannot be distinctly identified in the conduct. Not in itself giving origin to special acts, but serving simply to modify the acts otherwise originated, it can be discovered only by analysis of these.
The sole method, then, by which the progress of the correspondence in generality can be traced, is, to ascertain the conditions under which alone such a progress becomes possible; and then to show how the processes of evolution already described, necessarily give rise to these conditions. Let us do this.
§ 151. The recognition of a generality of this higher kind, embracing classes superficially dissimilar, implies a power of recognizing attributes as distinguished from the objects possessing them. Before any two fundamental properties that are found together under all varieties of size, form, colour, texture, temperature, motion, &c., can have their constant relation of coexistence responded to by the organism; it requires that the organism shall have an ability severally to identify these properties, as separate from their accidental accompaniments. The formation of simple class generalities, which group together phenomena that greatly resemble each other in all respects, requires no such distinct analysis of attributes. But where the resemblance is confined to some one essential relation common to many cases that in every other respect greatly differ, it is clear that unless the elements of this relation are separately cognizable by the organism, there can be no response to such relation.
Now it may readily be shown that the increase of the correspondence in speciality, must inevitably bring about this analysis of attributes—that there cannot be a continued multiplication of the distinguishable classes, without there being a simultaneous approach to the perception of properties in the abstract. For if, ascending from the lowest creatures by which but few attributes are cognizable, we step by step advance to those capable of being impressed by a greater and greater number of attributes—if, from the ability to distinguish large classes having but two or three attributes in common, we trace up the ability to distinguish the more special classes characterized by four, five, six, seven, &c., attributes in common, finally reaching the ability to distinguish individuals, which, while alike in the numerous attributes characterizing their species, differ only in one or two minor points; it is clear that in proportion as the groups of attributes become increasingly varied and special, there must be a more frequent dissociation of each particular attribute from others. Forms, colours, sizes, sounds, scents, motions, being found in all combinations—these two kinds of animals being alike in everything but colours; those two, similar in colour but different in form and scent; and the others having nothing in common but size—the property A occurring here in company with the properties B, C, D; there with C, F, H; there with E, G, B; and so on with each property to a greater or less extent—it must happen, that by multiplication of experiences, the impressions produced by these properties on the organism, will be gradually disconnected from each other, and rendered just so far independent in the organism as the properties are in the environment. Whence there must eventually arise a power to recognize attributes in themselves, as separate from particular bodies.
It may indeed be shown, that the advance of the correspondence in speciality, itself becomes possible only in proportion to the progress of this analysis. An analogy will best explain this. Suppose that a chemist, having the requisite ability and materials, be required to produce artificially a variety of compound bodies: what is implied in his successful execution of the task? The implication is, that he knows the composition of each of these bodies. But what does knowledge of their composition presuppose? It presupposes that they have been severally resolved into their constituents. It presupposes an acquaintance with the elements of which these and various other compounds consist. And the formation of each of the required compounds, implies that the component elements, having been previously separated from all other combinations, shall be put together in the right proportions. Well, the process of identifying any object as a thing having a special nature, is a synthesis of impressions, corresponding to the synthesis of perceptible properties which the thing displays; and similarly implies a recognition of the separate impressions which correspond with these separate properties. The botanist, who knows a particular flower, not by the fructification alone, in which it is like many others; not by the number of its petals, which is a very usual number; not by their forms, in which they do not differ from these, nor by their colours, in which they do not differ from those; not by the calyx, nor the bracts, nor the leaves, nor the stalk, separately considered; but by all these taken together; obviously effects the identification by a synthesis of attributes. And that which he does in this elaborate and conscious way, is done more or less completely in every case where an object is recognized as of special nature—is done in a degree proportionate to the speciality of the correspondence. Should it be said that this position, taken in connection with the previous one, involves a contradiction—that while the one represents the analysis of attributes as a prerequisite to speciality of correspondence, the other represents the analysis of attributes as resulting from increase of the correspondence in speciality—the reply is, that the two processes progress throughout in mutual dependence, perpetually acting and reacting on each other. Every advance in speciality must presently render the analysis of attributes more precise; and each step in the analysis of attributes renders possible a higher speciality.
Thus, then, we see that the course of evolution described in the previous chapters, is necessarily accompanied by a gradual disentangling of properties from each other; ending finally in an ability to recognize them in the abstract. The like process must later and more slowly take place with relations of sequence, as well as with relations of coexistence. An increasing speciality in the adjustments to mechanical changes, presupposes an increasing decomposition of those changes into their elements—a growing power to distinguish velocity of motion, direction of motion, acceleration and retardation of motion, kind of motion in respect of simplicity or complexity, and so on; and where non-mechanical sequences also come to be responded to, a parallel analysis must accompany a parallel progress in speciality.
The analysis of attributes having been carried to some considerable extent, there arises, and only then arises, a possibility of advance in generality of correspondence. Relations between properties possessed in common by objects of widely different kinds, can begin to be perceived as soon as these properties are separately cognizable. And it needs but a little reflection to see, that a still higher progress in the specialization of the correspondences, ultimately involves this remaining step required for generalization of them. For if, as we have seen, the continual multiplication of special correspondences must result in the gradual dissociation from each other of all variable attributes—beginning with the separation of those most inconstantly connected, and progressing to the separation of those less and less inconstantly connected; and if, when the variable attributes displayed by a group of different classes have been as it were disintegrated in the consciousness of the organism, the remaining attributes that have not been disintegrated must begin to stand out from the rest, as preserving a constant relation amidst all these inconstancies; we see that in the end, there must be established in the organism, a constant relation corresponding to the constant relation between these attributes; and this constitutes the advance in generality we are looking for. Add to which, that as the comparatively constant relations thus first generalized from the experience of but few classes, will, in the majority of cases, be proved by wider experience to be not everywhere constant; and as, by the accumulation of these wider experiences, the same process must be gone through with the comparatively constant relations, as before with the less constant ones, with the result of bringing the still more constant relations into view; the progress must necessarily be from narrow generalizations to wider and wider ones. And this we know, à posteriori, to be the law which the progress conforms to.
§ 152. These explanations will suffice at once to show how it happens, that the increase of the correspondence in generality, is scarcely discernible in any but the higher forms of intelligence. Necessary as it is that there should be a great advance in the speciality of the correspondences, to produce the requisite analysis of attributes; and necessary as yet further advance in specialization is, to bring into view the constantly related attributes as distinguished from the inconstantly related ones; it is only when that very high degree of speciality of correspondence characteristic of superior creatures is reached, that progress in generality of correspondence can begin. Hence the fact, that while the higher mammals undoubtedly display some generalities of correspondence of the least abstract kind, it is only when we come to the human race, that we find this species of adjustment of inner to outer relations, showing any considerable development.
Human progression, however, exhibits to us, under this, as under previous aspects, an immense increase in the harmony between the organism and its environment. Perhaps in no other respect is the increasing correspondence wrought out by civilization, so conspicuous, as in the growth of generalizations, ever more numerous and more comprehensive. The enormous expansion of science which these latter ages have witnessed, mainly consists in the union of many particular facts into general truths, and in the union of many general truths into truths still more general. It is needless to cite illustrations; for the proposition is familiar, and admitted by all. It will be enough simply to point to this great phenomenon as one of the many forms of the evolution we are tracing out.
A mere indication, too, of the extent to which the generalizations of science advance the arts, and through the arts minister to human welfare, will serve to show, that increase of the correspondence in generality, like its other modes of increase, makes possible a greater duration of life. And a like brief reference to the intense concentration of thought, and extreme complexity of conceptions, which these more abstruse generalizations imply, will sufficiently draw attention to the higher degree of life which must accompany this greater length of life.
THE CORRESPONDENCE AS INCREASING IN COMPLEXITY.
§ 153. Another change in our stand-point, affords us a view of vital progress, which, though not coextensive with foregoing ones, has much in common with them. As we saw that the extensions of the correspondence in Space and in Time, were in part reciprocal and in part not so; as we saw that the increase of the correspondence in Speciality, while to some degree comprised under the extensions in Space and Time, includes very much beside; so we shall find that while, throughout a certain range of cases, progress in Complexity is the same thing as progress in Speciality, yet neither includes all that the other does. Much of the early advance in Speciality does not imply advance in Complexity; and the higher forms of the advance in Complexity cannot without straining, be comprehended under advance in Speciality. But let us glance at the facts.
§ 154. In the progress from an eye that appreciates only the difference between light and darkness, to one which appreciates degrees of difference between them, and afterwards to one which appreciates differences of colour and degrees of colour—in the progress from the power of distinguishing a few strongly contrasted smells or tastes, to the power of distinguishing an infinite variety of slightly contrasted smells or tastes—in the progress from that lowest form of hearing, consisting simply in a response to any violent tremor of the surrounding fluid, to those higher forms of it in which differences of loudness are recognized, and by and by differences of pitch and timbre—in all those cases which present merely a greater ability to discriminate between varieties of the same simple phenomenon; there is increase in the speciality of the correspondence without increase in its complexity. The insect which lays its eggs only on a plant having a particular odour; and the bird which is alarmed by a tone of a certain pitch, but not by one of another; exhibit an adjustment of inner to outer relations, as simple as that seen in the snail which withdraws into its shell on being touched. Though the stimulus responded to is more special, it is not more complex. In each case a single undecomposable sensation, is followed by certain muscular actions: and though these muscular actions are more intricate in the higher creatures than in the lower; yet the relation between the antecedents and consequents, is very nearly, if not quite, of the same order. But where the stimulus responded to, consists, not of a single sensation but of several; or where the response is not one action but a group of actions; the increase in speciality of correspondence results from an increase in its complexity.
In the development of vision we see this repeatedly illustrated. When, in addition to the usual relation between opacity and solidity, first responded to, there arises a response to the relation between solidity and the power to reflect light—when differences in the amounts and qualities of reflected light come to be recognized in connection with differences of bulk—when there arises a power to identify objects, not only by colour and size conjoined, but by form—when surrounding things are grouped in more and more numerous classes, that agree with each other in such and such peculiarities, but differ in others; it is manifest that each successive stage implies the appreciation of larger clusters of attributes. The impression received by the organism from each object, is a more complex impression—is increasingly heterogeneous. And when not only colour, size, and shape become cognizable, but also direction in space, distance in space, motion, kind of motion, direction of motion, velocity of motion—when, as by a falcon swooping on its quarry, all these external relations are simultaneously responded to; it is clear that the guiding perception must be compounded of many elements. There is no need to dwell on this truth as further exemplified in the evolution of the other senses; nor to trace up in detail that yet higher complexity which results when the several senses are employed together. It suffices to cite an extreme case, such as that afforded by the mineralogist, who, in identifying a mass of matter as of a kind fitted for a certain use, examines its crystalline form, its colour, texture, hardness, cleavage, fracture, degree of transparency, lustre, specific gravity, taste, smell, fusibility, magnetic and electric properties, &c., and is decided in his conduct by all these taken together—it suffices to cite such a case as this, to show that throughout all the higher range of cases, increase in the speciality of the correspondence involves increase in its complexity.
§ 155. But, as already hinted, we eventually reach an order of correspondences in which the speciality and the complexity are no longer co-ordinate. A further advance in speciality is achieved by a much more than proportionate advance in complexity. In these cases, the adjustment of particular actions to particular circumstances, involves a far more extensive pre-adjustment of inner relations to outer relations, than is directly displayed. Let us look at an example or two.
The archer, who points his arrow, not at the object he seeks to hit, but above it, and who varies the angle of elevation according as the object is far or near, exhibits something more than a special response to special stimuli; for his procedure implies recognition of the fact, that bodies projected through the air, descend towards the earth, and that the amount of their descent has some relation to the distance traversed. Besides a correspondence with certain sensible relations in the environment, there is implied a correspondence with the law of certain other relations, not then present to the senses. Again, to take a more marked case:—the engineer who erects a suspension-bridge competent to bear a specified strain, is enabled to adjust his actions to the requirements, less by his inspection and measurement of the river to be crossed, than by his knowledge of the strength of wrought iron, of the properties of the catenarian curve, of the composition of forces—his acquaintance with the universal truths of number, geometry, mechanics. In these cases the complexity of the correspondence is greatly in excess of the speciality. To bring out this fact by a contrast:—It might fairly be said that the Indian fish which catches insects flying over the surface by hitting them with jets of water, exhibits a correspondence as special as that seen in the archer; but considering that in the fish, the action implies nothing more than an automatic connection between certain visual impressions and certain muscular contractions—any modification of the one itself causing a modification of the other—it cannot be held that there is anything like the same complexity of correspondence. And similarly, though it might be plausibly argued that the strength of a spider's web is as specially adjusted to the demands to be made upon it, as is that of the engineer's suspension-bridge; yet it will not be contended that there is any comparison between them in respect of the variety and elaborateness of the actions implied.
If now we inquire whence arises this excess of complexity; we find that it is caused by the addition of generalities to specialities. Each of these higher correspondences displaying what we call rationality, implies an adjustment of inner relations not simply to the concrete outer relations then present; but to one or more of those abstract relations among external things, which previous experience has generalized. And as we advance to correspondences of still greater and greater complexity, we see that their leading characteristic is the increasing number of the abstract relations recognized, and involved in the process of adjustment. In these cases, there is a response, not simply to the particular phenomena presented in one part of the environment; but there is, as it were, a simultaneous response to sundry of the general phenomena presented by the environment at large. When we reach the highest achievements of science, as especially exemplified in astronomy, it becomes obvious that an exact adaptation of the actions of the organism, to special actions in the environment, implies the pre-establishment of general relations in the organism, parallel to all those general relations in the environment which are in any way implicated with the phenomenon.
§ 156. There seems no place fitter than this, for drawing attention to the fact which has not yet been noticed, and which it is yet very important to notice, that there is a more or less constant ratio maintained between the impressibilities and the activities of the organism, in so far as their complexity is concerned. Considered under its most general form, every correspondence effected between the organism and the environment, involves two things—the reception of one or more impressions, and the performance of one or more appropriate motions. In the lowest animal types, we see a touch followed by a withdrawal of the part touched—a single impression followed by a single action. Gradually as we ascend, we observe an ability to receive increasingly complicated impressions, and to perform increasingly complicated actions. And the truth here to be observed, is, that the heterogeneity of the stimuli that can be received, is in general proportionate to the heterogeneity of the changes that can be displayed.
Before passing to the rationale of this, it may be well to remark, that from a teleological point of view, no other arrangement is admissible. As every advance in the correspondence between the organism and its environment, consists in the addition of some further internal adjustment to some further external relation; and as the ability to recognize the external relation is useless unless there is an ability to appropriately modify the conduct; it is clear that for the better preservation of life, the passive and active elements of the correspondence must progress together in speciality and complexity. A power to perceive the position of an object in space, must be accompanied by a power to specialize the movements; otherwise it can be of no service. The recognition of certain forms, colours, and motions as those of an enemy, will not prevent destruction unless it be followed by such velocity of motion, such doublings, such leaps, as the enemy may be eluded by. The discrimination shown by a bird in the choice of materials for its nest, is so much faculty thrown away, unless there be sufficient constructive skill for nidification. It will not benefit the savage, to discover at what seasons and what times of the tide particular fish are to be caught, unless he has dexterity enough to make and use the apparatus needful for catching them. And so throughout, it must on the average happen, that every further differentiation of the perceptions, opening the way for a further differentiation in the actions, fails of its purpose unless an ability further to differentiate the actions is associated with it.
Leaving, however, all thought of ends to be subserved, we shall find the true explanation of this connection between progress in the impressibilities and progress in the activities, is simply that each necessitates the other—that they so act and react, that the advance of either involves the advance of both. The general relation between irritability and contractility, which, in the lowest types of animal life, constitute one indivisible phenomenon, is a relation which the sensitive and the active divisions of the organism, maintain throughout all their complications. They are co-ordinate in their origin; they are co-ordinate in their manifestations; they are co-ordinate in their progress. As certainly as the nervous and muscular systems make their appearance together; as certainly as, throughout the whole animal kingdom, they preserve a general parallelism in degree of development; so certainly is there an indissoluble connection between their respective functions in point of advancing complexity.
A general conception of this law will best be obtained by regarding the two functions under their most abstract forms—sensation and motion. Given an organism with certain sensory and motor faculties, and what must happen from the increase of either? Higher powers of motion and locomotion, must unavoidably bring the organism into relation with a greater number of objects; and must so result in multiplying its impressions. Higher sensitiveness in the organism, must unavoidably entail more frequent stimuli to action; and must so multiply its motions and locomotions. Again;—The more varied a creature's activities, the more varied must be the relations in which it puts itself towards surrounding things; and hence the more varied must be the modes in which surrounding things affect it. And, conversely, the greater the variety of impressions receivable from surrounding things, the greater must be the number of modifications in the stimuli given to the motor faculties; and hence, the greater must be the tendency towards modified actions in the motor faculties. Thus, in respect both of activity and complexity, the progress of each is involved with the progress of the other.
But the necessity of this simultaneous development of the directive and executive faculties, will be most clearly seen on analyzing a few cases. Take as one, the ability to recognize direction in space. At first this may be thought to imply a development simply of the sensitive part of the nature—simply an expansion of the retina sufficiently great to admit of its several parts being separately affected by images falling upon them. But a little consideration will show, that something more is required than ability to perceive differences in the position of the image on the visual tract. Taken alone, these differences are meaningless: they come to have meaning, only when they are severally connected in the organism with those differences of motion required to bring the surface into contact with the things seen. As all psychologists admit, mere ocular impressions do not of themselves give any ideas of space. These arise, only when, by a growing experience, the impressions are referred to objects that can be touched by special muscular adjustments. Direction, therefore, cannot be perceived until there is not only a motor apparatus, but one so far developed as to effect specialized movements. And thus, the ability to perceive direction, and the ability to take advantage of the perception, are necessarily connate. The recognition of distance, of velocity, of bulk, of shape, so obviously imply the like conditions, as merely to need mention. Again, differences of light and shade cannot be known to indicate variations of surface, until these variations have been disclosed by corresponding variations in the adjustments of the muscles; and so, complex muscular adjustments must be possible, before complex variations of light and shade can be interpreted. No definite idea of weight, as connected with visual appearances, can be arrived at, until there is a power of lifting, either by the jaws or limbs. Nor can differences of hardness and texture be assigned to surrounding objects, faster than the manipulative organs are perfected. And indeed, as these last instances suggest, it is not simply that the impressions made upon the senses require to be connected with the muscular experiences, before their meanings can be made out; but it is that the impressions themselves, in their higher forms, cannot be received without muscular aid. Perfect vision implies a focal adjustment of the eyes, an adjustment of their axes to the requisite convergence, a turning of them both towards the object, sometimes a turning of the head in the same direction, and sometimes also a turning of the body; all of which preparatory acts are performed by the muscles; and the last ones, not by the muscles of the eye, but by those of the body at large. Neither taste nor smell are possible unless the muscles of the tongue and the chest do their parts. Even hearing is imperfect unless the membrana tympani is strained by its muscles into concord with each successive sound. But above all, the knowledge acquired through the sense of touch, is especially dependent upon the motor apparatus. The mere existence of a sensitive skin, is but a small part of the requirement; as any one may prove by closing his eyes and applying his bare arm or leg to an unknown object. For the tactual impressions to be such as will give ideas of extension, form, solidity, this sensitive skin must be distributed over surfaces capable of deriving simultaneous or rapidly succeeding sensations from different parts of the things touched; and these sensations must be combined with those muscular sensations accompanying the simultaneous and successive adjustments of the sensitive surfaces. There must be limbs to effect the larger and simpler adjustments; and appendages to them to effect the smaller and more elaborate ones. And only in proportion as these motor agencies become complex and complete, can there be completeness and complexity in the tactual perceptions. But these motor agencies—these limbs and appendages, with all the muscles they are moved by, are also the locomotive and manipulating organs; and the same elaborateness of structure which fits them to receive compound impressions, also fits them to perform compound operations. Thus, the evolution of the sensitive or directive apparatus, is inseparably involved with the evolution of the muscular or executive apparatus.
And here we may fitly notice a group of facts serving to illustrate this general law—facts exhibiting in the concrete, this constant relation between the impressibilities and the activities in respect of their complexity. I refer to the sundry striking instances, presented throughout the animal kingdom, of unusual sagacity coexisting with unusual development of the tactual organs. Why touch, which is in itself the simplest and earliest sense, should, in its higher forms, be more than any other sense associated with the advance of intelligence, will perhaps seem difficult to understand. The explanation lies simply in the fact, that tactual impressions are those into which all other impressions have to be translated, before their meanings can be known. If we contemplate the general relation subsisting between the organism and surrounding objects, we see that before they can affect it, or it can affect them, in any important way, there must be actual contact. Assimilation, respiration, locomotion, the destruction of prey, the escape from enemies, the formation of nests and burrows, the bringing up of young—all the essential functions, when considered in their ultimate natures, imply mechanical action and reaction between the organism and its environment. The space-penetrating faculties serve but as guides to this mechanical action; and the impressions they receive, are primarily used but as symbols of tangible properties and relations. Hence it happens, that only as fast as the mechanical impressions, recognized by the muscles and the skin, become varied and complex, can there be a complete translation of the varied and complex impressions recognized by eyes, ears, and nose. The mother tongue must be as copious as the foreign; otherwise it cannot render all the foreign meanings. And thus, as seen in the facts referred to, a highly elaborated tactual apparatus comes to be the uniform accompaniment of superior intelligence. But let us look at these facts.
Just to show that each great family of the animal kingdom supplies them, I may mention in passing, that the Cephalopoda, which in point of sagacity are far in advance of other Mollusca, are structurally distinguished from them in having several arms by which they can grasp an object on all sides, at the same time that they apply it to the mouth; and again, that the crabs, which similarly stand at the head of the sub-kingdom Articulata, can bring their claws and foot-jaws simultaneously to bear upon anything they are manipulating. But merely glancing at these, let us content ourselves with examples supplied by the vertebrate tribes. It will be admitted that, of all birds, parrots have the greatest amount of intellect. Well, if we examine in what respect they are structurally most distinguished from other birds, we find it to be in development of the tactual organs. Few birds have such power of prehension with the feet, as to be able to grasp and lift up an object with the one foot, while standing on the other. The parrot, however, does this with ease. In most birds the upper mandible is scarcely at all moveable. In the parrot it is moveable to a marked extent. Generally, birds have the tongue undeveloped, and tied down close on the lower mandible. Parrots, however, have it large, free, and in constant employment. Above all, that which the parrot grasps in its claw, it can raise to its beak; and so bring both mandibles and tongue to bear upon what its hand (for it is practically a hand) already touches on several sides. A moment's consideration suffices to show, that no other bird approaches to it in the complexity of the tactual impressions it can receive; and thus, advance of the directive faculties is manifestly involved by advance of the executive ones.
Among quadrupeds, again, it is unquestionable that as a general rule the Unguiculata, or those that have the limbs terminating in separate digits, are more intelligent than the Ungulata, or hoofed animals. The feline and canine tribes stand psychologically higher than cattle, horses, sheep, and deer. Now it is obvious that feet furnished with several sensitive toes, are capable of receiving more complicated impressions than feet ending in one or two masses of horn. While, by a hoof, only one side of a solid body can be touched at once; the divided toes of, for example, a dog, can simultaneously touch the adjacent sides of a small body, though not the opposite sides. And if we further bear in mind that the higher kinds of toed quadrupeds, while they cannot grasp with their feet, can nevertheless use them for holding down what they are tearing or gnawing with the teeth; we see that they can recognize tangible relations of considerable complication. Add to which the fact, that when, among the hoofed animals, we meet with any marks of sagacity, as in the horse, we find that the lack of sensitive extremities is in some measure compensated for by highly sensitive and mobile lips, which have considerable power of prehension. And here, indeed, we are naturally reminded of the most remarkable, and perhaps the most conclusive instance, of this connection between development of intelligence and development of the tactual organs—that seen in the elephant. I say most conclusive, because the elephant is markedly distinguished from allied tribes of mammals, alike by its proboscis, and by its high sagacity. The association between the operative and cognitive faculties stands out the more conspicuously, from the endowment of both being exceptional. On the intellect of the elephant there is no need to dwell: all know its superiority. The powers of its trunk, however, must be enumerated. Note first, its universality of movement, in respect of direction. Unlike the ordinary mammalian limbs, whose motions are more or less confined to the vertical plane, its flexibility gives it as wide a range of positions as the human arm can take—wider, indeed, than can be taken by a single arm: and thus the elephant can ascertain the relations in space, both of its own members and of surrounding things, more completely than all other creatures, save man and the higher quadrumana. Again, the trunk can grasp bodies of every size, from a pea to a tree stump; and by this means can ascertain the tangible forms of a greater variety of objects than any of the lower mammalia. The finger-like projection with which the trunk terminates, receives impressions of the minor variations of surface; and so, textures and the details of shape can be made out, as well as general extension. Moreover, the complete prehensile power, giving ability to lift bodies of many sizes and natures, opens the way to a knowledge of weight, as connected with visible and tangible properties. The same power of prehension, used as it habitually is for the breaking-off of branches, brings experiences of the tenacity and elasticity of matter; and when employed, as these branches often are, for driving away flies, the swinging of them about must supply vague impressions even of momentum—impressions which the ability to throw small bodies (as gravel over the back) must tend to strengthen. Further, the trunk's tubular structure fits it for a number of hydraulic experiments, and so gives a knowledge of the mechanical properties of water, such as no other quadruped can attain to; and this same peculiarity, rendering it possible to send out strong blasts of air, producing motion in the light bodies adjacent, opens the way to yet another class of experiences. Thus, the great diversity of tactual and manipulatory powers possessed by the elephant's proboscis, is not less remarkable than is the creature's high sagacity—a sagacity which, dwelling in so ungainly a body, would otherwise be altogether inexplicable.
Passing to the quadrumana, we find repeated, under other forms, this same relation between development of the intelligence, and development of the tactual appendages. It is seen not only in the contrast between them and inferior mammals; but it is seen in the contrasts between the subdivisions of the quadrumana themselves. The prehensile and manipulatory powers of the lower genera, are as imperfect as are their mental powers. As we advance to the highly intelligent anthropoid apes, we find the hands so modified as to admit of more complete opposition of the thumb and fingers; the bones of the forearm so articulated as to give the hand a power of rotation; the arms attached to the body in such a manner as allows them an increased range of lateral movement. And when, as in all the more perfect of the class, the structure of the fore-limbs is so complete, that an object can be grasped in one hand, while it is being manipulated with the other, or by the lips and teeth—can be held at the most convenient distance from the eyes—can be applied to any part of the body, or any neighbouring object—it is manifest, that more complex perceptions, of size, shape, structure, texture, hardness, weight, flexibility, tenacity, in their various combinations, can be received, than are possible to creatures whose limbs are less elaborately constructed. And thus the mutual dependence of the operative and cognitive faculties becomes clearly apparent.
How, in man, both exist in yet higher perfection, scarcely needs saying. As contemplated from an obverse point of view, the connection between them is abundantly exemplified in works on natural theology. All that it is desirable here to notice, is, the extent to which, in the human race, this perfection of the tactual apparatus has subserved the highest processes of the intellect. It is not simply that the tangible attributes of things have been rendered completely cognizable by the complex and versatile adjustments of the human hands—it is not simply that the greater knowledge of objects thus reached, opened the way for the making of tools, and consequently for agriculture, building, and the arts in general—it is not simply that by these were made possible, the settled and populous societies without which none of the higher forms of intelligence can be attained to; but it is, that the manipulative powers directly underlie the sciences, including even the most remote and abstract. All developed science, consisting as it does of quantitative prevision—dealing as it does with measured results, is lineally descended from that simplest kind of measurement achieved by placing side by side the bodies held in the hands. Our knowledge of the forces governing the solar system, is expressed in terms that are reducible, by an ultimate analysis, to equal units of linear extension (§ 27), which were originally fixed by the direct apposition of like natural objects.∗ And the undeveloped sciences, consisting as yet of qualitative prevision, depending for their advance, as they do, either upon experiments requiring apparatus and skilful manipulation, or upon observations involving dissection and other analogous procedures, have similarly implied a highly-developed manual dexterity. Thus, the tactual apparatus not only serves in its lower forms to establish relations between the tangible and non-tangible attributes of things; but, in its highest forms, it indirectly serves to establish relations among the non-tangible attributes themselves.
This intimate connection between the impressibilities and the activities—between the directive and executive faculties, which we have traced in the first improvements of perception and locomotion, which we have seen exemplified in various creatures distinguished alike by their high intelligence and their developed organs of manipulation, and which we find to hold even with the human race—this mutual dependence of the cognitive and operative powers, which Anaxagoras had a glimpse of when he uttered his hyperbolical saying that animals would have been men had they had hands; is a relation yet more remarkably and more conclusively exemplified, in the reciprocity of aid exhibited by the Sciences and Arts. Strange as the proposition will at first sight seem, it needs but a little analysis to show, that the Sciences and Arts, when regarded subjectively, severally represent what in inferior creatures we call sensory and motor processes. The perceptions gained through the sensory organs and the actions performed by the motor ones, respectively become, under their most complex forms, scientific generalizations and manufacturing operations. A comparison of the extremes does not very obviously display this; but on looking at the transitions the filiation becomes manifest. It cannot be denied that the two attributes of irritability and contractility, possessed by all but the very lowest animal types, are the respective bases of the sensitive and motive faculties—that the senses exhibit subdivisions of the one, and the muscles specializations of the other. It cannot be denied that the increasingly complex perceptions to which each sense becomes the medium, together with the still more complex perceptions achieved by the union of several senses, are forms of the organism's impressibility; nor that the successive complications of motive, locomotive, and manipulative powers, are forms of the organism's activity. It cannot be denied that out of these more complex perceptions, woven into still more extensive combinations, finally arise the previsions of science; nor that all handicrafts, and after them the higher processes of production, have grown out of that manual dexterity in which the elaboration of the motor faculty terminates. And thus it cannot be denied, that sensation and the sequent motion are the prototypes of Science and Art. If, looking at the entire range of phenomena under their most general aspect, we consider the fundamental nature of the changes by which an organism adjusts itself to the environment; if we divide these changes, as we must, into those which external objects impress upon it, and those by which it appropriately modifies its relations to the external objects; if we name these respectively, the directive changes and the executive changes; we clearly see, that sensations, perceptions, conceptions, generalizations, and all forms of cognition, come under the one; while contractions, locomotions, and all kinds of operations, come under the other; and that Science and Art, so far as they are separable at all, belong, the one to the first division, and the other to the last.
This truth being duly recognized, we shall at once see the significance of the fact, that throughout the course of human progress, there has been a reciprocity of services between the Sciences and Arts like that which we have traced out between the impressibilities and activities—a continuation of the same mutual dependence. History presents no generalization more certain, than that each great step towards a knowledge of the laws of things, has facilitated men's operations on things; while each more successful operation, has, by its results, facilitated the discovery of further laws. Astronomy and agriculture; geometry and the laying out of buildings; mechanics and the weighing of commodities; were among the earliest relations of the two. Presently, geometry, as developed by artificers, acted upon astronomy; and astronomy reacted to the great advancement of geometry. Through the medium of the scales, mechanics, joined with the science of number, influenced the metallurgic arts, gave definite alloys, introduced metallic instruments; and by so doing, both advanced the accuracy of astronomical and other observations, and improved all those processes of production for which metallic tools are employed. Metallurgy too, by supplying plane and concave mirrors, initiated optics; and the first proposition in harmonics was reached by the strings and weights which the arts furnished. Not to trace out this reciprocity in detail, it requires only to look at its modern manifestations, in the dependence of navigation on astronomy, magnetism, and meteorology; and the aid rendered to magnetic and meteorologic science by navigation—in the development of geology by mining, quarrying, and well-sinking; and the guidance which geology now gives in the search for coal, metals, and water—it requires but to observe how the definite compounds and elements with which chemistry deals, were at first brought to light by the arts; and that the arts are now all more or less dependent on chemistry—it requires simply to consider that there is scarcely a single observation at present made in science, but what involves the use of sundry instruments, supplied by the arts; and scarcely a single art-process but what involves some of the previsions of science—it requires but to glance at these relations, to perceive, not only that the reciprocity exists, but that it has been ever becoming more active. And this last fact yet further elucidates the general truth we are contemplating. For, as we found when tracing upwards the directive and executive faculties, that in their higher developments they become more and more mutually dependent—that the completer forms of visual and tactual perception are impossible without complex muscular adjustments, and that the more elaborate actions require the constant overseeing of the senses; so, we now find that in the development of these still higher cognitive and operative processes, the advance is towards a reciprocity so active that each further cognition implies elaborate operative aid, and each new operation implies sundry elaborate cognitions.
Still more clearly will these correlations be perceived, on regarding them under their concrete aspect. From our present point of view we may properly say, that in its higher forms, the correspondence between the organism and its environment, is effected by means of supplementary senses and supplementary limbs. Whether a man crushes an object with his hand, with his teeth, with a vice, or with a hydraulic press, matters not in so far as the relation between the stimulus and the action are concerned; nor does it affect the fundamental nature of the perception, whether the relative lengths of two lines are determined by simple inspection, or by placing them side by side, or by means of a pair of compasses. Thus, all observing instruments, all weights, measures, scales, micrometers, verniers, microscopes, thermometers, barometers, &c., are artificial extensions of the senses; and all levers, screws, hammers, wedges, wheels, lathes, &c., are artificial extensions of the limbs. The magnifying glass adds but another lense to the lenses existing in the eye. The crowbar is but one more lever attached to the series of levers forming the arm and hand. And the relationship which is so obvious in these first steps, must hold throughout. This admitted, and the reciprocity which we have traced between the higher cognitive and operative processes, will be yet more distinctly seen between their respective organs. The development of these supplementary senses, is dependent upon the development of these supplementary limbs; and vice versâ. Accurate measuring instruments, presuppose accurate instruments for turning and planing; and these cannot be made without the aid of previous measuring instruments of some accuracy. A first-rate astronomical quadrant can be produced only by a first-rate dividing engine; a first-rate dividing engine can be produced only by first-rate lathes and cutting tools; and so, tracing the requirements backwards, it becomes obvious that only by often repeated actions and reactions upon each other, can either directive or executive implements be brought to perfection. Only by means of artificial limbs can artificial senses be developed; and only through artificial senses does it become possible to improve artificial limbs.
These truths—this affiliation of the Sciences and Arts upon the lower forms of cognition and action; and this mutual dependence of the Sciences and Arts, whether considered in their respective processes or the agencies by which those processes are achieved—throw back a strong light upon the primitive connection of the impressibilities and activities. That reciprocity which we found to exist between these in their simpler forms, is a reciprocity which becomes yet more certain on discovering that it holds between those highest manifestations of the directive and executive powers displayed in human progression. When, after seeing how multiplied motions must produce multiplied sensations, and conversely—when after tracing up the like relation between increasingly specialized perceptions and increasingly specialized actions, we find it to obtain between these most complex cognitions and those most complex operations which we term Science and Art—and when we see, not only that these have developed together, but, by tracing their actions and reactions upon each other, also see that neither could have advanced separately—when we see all this, it becomes an irresistible conclusion, that there exists throughout, that mutual dependence which analysis and induction indicate. It becomes an irresistible conclusion, that as discoveries in Science have improved the Arts, and improvements in the Arts facilitated discoveries in Science; so, from the beginning, each more developed impressibility has aided the activities, and each advance in the activities has opened the way to higher impressibilities.
Returning now from this long but needful digression, to our immediate topic—the increase of the correspondence in complexity—we perceive how, as was alleged, the two divisions of it simultaneously pass through parallel phases. Starting from the production of a single contraction by a single irritation, and step by step ascending to more heterogeneous motions and more heterogeneous stimuli; we find, in all stages, a more or less constant ratio preserved. Indeed, we may almost say, that, à priori, a complex operation is impossible without a complex cognition to guide it; while, conversely, a complex cognition is impossible without the experiences derived from complex operations: and so we may argue, that this duplexity in the progress is necessary. Moreover, it may be remarked, that not only do the directive and executive elements of the correspondence, develope hand in hand; but the kinds of complication they eventually assume are of analogous characters. That union of generalities with specialities which we found to distinguish the highly elaborated cognitions of Science, is visible also in the highly elaborated operations of Art. Just as a particular conclusion in Science, is reached by applying to special data a general principle, which general principle applied to other data, gives other conclusions; so, a particular product of Art, is obtained by subjecting to special manipulations, the results of some more general process, which results of some more general process, subjected to other manipulations, yield other art-products. And thus the parallel holds, not only between the degrees of these mutually-dependent complexities, but also between their kinds.
§ 157. That this increase of the correspondence in complexity, exhibited in the ascending developments of Life in general, has continued throughout human civilization, we have incidentally seen in the course of the above argument. The gradual evolution of Science and Art, just traced out with another aim, so abundantly exemplifies this, as to render further exposition unnecessary. There is, however, one aspect of this progress which it may be well to notice; namely—the advance that has taken place, not simply in the complexity of the cognitions and operations that have been age by age attained to, but in the ability to receive complex cognitions and perform complex operations.
For it is not, as most suppose, that scientific and artistic progress, is due simply to the accumulation of knowledge and of appliances; but it is that the impressibilities and activities have themselves grown to a higher complication. There is distinct evidence from various quarters, that the minds of the inferior human races, cannot respond to relations of even moderate complexity; much less to those highly complex relations with which advanced science deals. According to the traveller, Lieutenant Walpole, it is remarked of the Sandwich islanders, by their teachers, “that in all the early parts of their education, they are exceedingly quick, but not in the higher branches; that they have excellent memories, and learn by rote with wonderful rapidity, but will not exercise their thinking faculties.” That is to say, they can readily receive simple ideas, but not complex ones. Again, it is asserted of the Australians, that “some of them are very quick at acquiring knowledge, but they have no power of combination or concentration.”∗ The reports of Hindoo schools, disclose, though in a less marked manner, the same fact. And according to Mr. W. Chambers, one of the reasons assigned by the Americans for not educating negro children along with white children, is, that after a certain age they “do not correspondingly advance in learning—their intellects being apparently incapable of being cultured beyond a particular point:” an allegation, which, though liable to the suspicion of partisan bias, so far accords with the independent statements previously quoted, as doubtless to have some basis. In all these cases, as also in the minor cases continually occurring among ourselves of inability to understand subjects and reasonings passing a certain order of abstruseness, the true interpretation is, that the cognitive faculties have not reached a complexity equal to the complexity of the relations to be perceived. Moreover, it is not only with purely intellectual cognitions that this holds; it holds also with what we distinguish as moral cognitions. In the Australian language there are no words answering to justice, sin, guilt. Among various of the lower races, acts of generosity or mercy are utterly incomprehensible. That is to say, the more complex relations of human action in its social bearings, are not cognizable. And thus, the large-brained European differs from the small-brained savage, not simply in the complexity of his manifestations, intellectual and moral; but these have been step by step made possible by successive complications of faculty.
Having, in the previous chapter, pointed out how greater length and higher degree of life, accompany increased speciality and increased generality of correspondences; it needs not to dwell on the fact that where both these unite in producing correspondences of increased complexity, the like result must happen. All that requires just indicating, is, that not only is this true of those more and more complex cognitions, which, through the medium of Science, advance the Arts; but it is true of those more complex moral cognitions, which, by making social order possible, contribute to that greater individual safety which social order brings.
THE CO-ORDINATION OF CORRESPONDENCES.
§ 158. Fully to comprehend the increase of the correspondence between the organism and its environment, in speciality, in generality, and in complexity; it is requisite to contemplate the phenomena under yet another aspect. We must look at the general conditions by fulfilment of which these more elaborate adjustments of inner to outer relations are made possible. The performance of a compound action in response to a compound impression, implies something more than a susceptibility to each of the several elements constituting the compound impression, and a power to effect each of the several motions constituting the compound action. It implies also, that the constituent sensations and contractions shall be combined after a particular manner—shall be co-ordinated; and the perfection of the correspondence will vary as the perfection of the co-ordination.
Let us take first a simple case; as that of the actions needed for escape from an enemy. Clearly when we ascend from those creatures in which the motion of some conspicuous adjacent object is responded to simply by a few random muscular movements, to those creatures in which the muscular movements are such as to carry the body away from the dangerous object; we have advanced to an adjustment of at least two conjoined relations in the organism, to two conjoined relations in the environment. If we consider the strong visual impression produced by the adjacent moving object, to be the stimulus to activity; then, that the activity may be of the right kind, it is requisite that such particular modification of the impression as depends on the direction of the object in space, should also be recognized, and the activity modified in conformity to it. The impression which indicates dangerousness, and that which indicates position, must together control the motor changes; and the control must consist in so ordering their respective amounts, that the composite result may be a movement of the organism in a particular line. When distance, as well as direction, becomes cognizable; and when the colour and shape of the object can be distinguished, as well as its mass; the stimulus must be composed of a much greater number of elements, united after a special manner: and in proportion as the consequent actions become more rapid, skilful, and varied, must there be a more elaborate and more perfect combination of motor changes. While just as a wrong combination of motor changes involves a fall or other accident; so, a wrong combination of the separate stimuli involves a mistaken perception.
Space need not be occupied in tracing up these simple kinds of co-ordination. It is obvious that throughout the whole series of increasingly heterogeneous impressions comprehended within the limits of immediate perception, including even the recognition of localities by an identification of the various surrounding objects, the component elements of the impressions co-operate after a particular manner; and that, as especially seen in this case of localities, it is only in virtue of a definite relationship among them, that a definite perception is possible. It is equally obvious, that the more and more complex actions by which higher creatures achieve their ends, succeed, only in as far as the muscular contractions implied, are fitly regulated in their order, their amounts, and their modes of conjunction. Both the directive and executive processes can become efficient, only in proportion to the accuracy with which they are co-ordinated.
§ 159. Advancing from these cases in which the directive stimuli, though heterogeneous, are made up of elements that are simultaneously present to the senses, to the cases in which some of their elements are present to the senses and some not; we meet with a co-ordination of a new and higher order. And so likewise where the responding motions, no longer occurring in an inseparable group, are divided by intervals that vary according to circumstances, we see a parallel progress. A creature which, when pursued, flies to its burrow, or towards some distant unseen shelter, supplies us with an instance of the one; while an instance of the other occurs in any process, which, like the building of a nest, is effected by instalments variously interrupted by other procedures. From the stage in which a single past impression unites with many present ones to compose a special stimulus, and in which the action completed at intervals is tolerably homogeneous in character; the progression is gradually towards a union of many past impressions with present ones, and towards a species of action increasingly heterogeneous in its successive instalments, and in the manner of their succession. In the majority of men's daily proceedings, we see the sights, sounds, and muscular sensations, serving for immediate guidance, co-ordinated with recollections of the persons, places, things, events, to which those proceedings refer: and in such an error as that of mistaking the hour at which certain business is to be transacted with certain people at a certain office, we see how a failure arises from an imperfect co-ordination of the various past and present impressions constituting the directive stimulus. Further, in such a series of operations as those by which wheat is sown, weeded, reaped, stacked, thrashed, winnowed, taken to market, and sold; we see sundry widely different groups of actions (each consisting of many minor groups), divided by dissimilar and variable intervals, all adjusted to the achievement of a single end; and success requires that they shall be adjusted in a particular manner. Obviously the elaborateness displayed by these advanced cognitions and actions—in which time past, time present, and time future are alike involved; and which have simultaneous reference to sundry places in space,—is an elaborateness measured by the number of past impressions compounded with present ones. And obviously, throughout the whole of this order of correspondences, the all-essential thing is, neither the multiplicity of the impressions received, nor the complexity of the combination into which they enter, but the definiteness with which that combination is adapted to the combination of external circumstances—the goodness of the co-ordination.
§ 160. A still higher species of co-ordination, growing imperceptibly out of the last, and vaguely seen even in the illustrations just given, involves not simply the union of past with present specialities, but the union of generalities with both. The impression received yesterday, when the barometer stood at “Fair;” together with the impression received to-day, when it stands at “Change;” have to be joined to the generalization that a fall of the mercurial column indicates rain; before any conclusion can be drawn for to-morrow's guidance. In other cases, as in that of a physician prescribing for his patient, several remembered observations of the bygone symptoms; several observations of the existing ones; and several general truths, serving to interpret the changes that have taken place; must all enter into that directive process which terminates in an appropriate course of treatment.
But the most developed form of co-ordination is that exhibited by quantitative science. In this, not only must many specialities be combined with many generalities after a perfectly definite manner; but there must be perfect definiteness in each constituent of the combination. The perceptions by which the data are obtained, must have their elements so exactly co-ordinated, as to give measured results. The laws of dependence must be so cognized, that they can be expressed numerically. And the process by which, out of data and laws, the prevision is finally evolved, must have each step united with preceding and succeeding ones, in a mode that is completely specific. A calculation of the capacity of a vessel which a given horse-power will move at a given speed, involves the general truths,—that the resistance encountered by a body moving through fluid varies in the square of the velocity; that the area opposed to the water varies as the squares of the dimensions of the vessel; that the tonnage varies as the cubes of the dimensions; with sundry others. Particular forces, weights, specific gravities, lengths, breadths, depths, have to be combined with these general truths, each with each; and the results have to be further combined after particular modes. If one of the generalities be applied to the wrong specialities—if the formula for resistance be brought to bear, not in the figures representing sectional area, but on those representing tonnage—if the data be inexact, or the principles be misunderstood, or the calculation be erroneously performed; that is—if there be an imperfect coordination of the various mental acts involved; a false result is reached: there is a failure in the act of cognition: the internal relations are not so adjusted as to match external ones. And here, indeed, is most distinctly shown the nature of this process by which all the more complex adaptations of the organism to its environment are effected. For this quantitative prevision, in the achievement of which the co-ordination of intellectual actions is so conspicuous, is, as we have already seen (§ 148), simply the highest form of correspondence—the correspondence that is the most complete, the most special, the last to make its appearance—the correspondence by which external phenomena are conformed to, not only in kind, but in time, place, amount, duration: and the perfect co-ordination by which this perfect precision of result is effected, is simply the final development of the co-ordination which has, to a greater or less degree, existed throughout. As perfect correspondence implies perfect co-ordination; so, each degree of correspondence implies a parallel degree of co-ordination.
It will further elucidate both this doctrine of co-ordination and the general doctrine of correspondence, if we consider how, for the perfect adjustment of inner to outer relations, there must necessarily exist in the first, elements and changes representing all the elements and changes in the last. The cognitions of exact science are distinguished from inferior cognitions in this; that the mental process involves a symbol answering to every constituent of the phenomenon. Undeveloped life is guided by the associations among some of the superficial attributes of things. Developed life is guided by the relations subsisting among all those fundamental attributes on which the actions of the things depend. There is no invariable connection between a loud sound and an adjacent enemy; and hence, creatures in which one of these serves as an index to the other, are occasionally wrong in the adjustment of their internal relations to external ones. But the connection between linear dimensions and solid content, or between velocity and momentum, is of that constant, or, as we say, necessary nature, that, once known, it affords infallible guidance. For this infallible guidance to be had, however, requires that all the elements of the relation be cognized. Whenever a group of inner relations, a cognition, is completely conformed to a group of outer relations, a phenomenon, by a rational process—whenever there is what we call an understanding of the phenomenon; it is that the genesis of the phenomenon is, in a sense, paralleled by the genesis of the cognition: and that this may be possible, it is requisite that every component of the one process, be represented by some component of the other. The law, that the momentum of a moving body varies as its velocity multiplied into its weight, cannot be known until there exists in the mind, not only the conceptions answering to momentum, velocity, and weight; not only the processes of thought answering to those quantitative phenomena which “varies as” and “multiplied into” indicate; not only the ideas of matter, time, and space, without which velocity and momentum are inconceivable; but the law cannot be known until the states of consciousness symbolizing time and space, are so co-ordinated as to symbolize velocity; the states of consciousness symbolizing velocity and weight, so co-ordinated as to symbolize momentum; and these three again co-ordinated according to those laws of relation implied by “varies as” and “multiplied into.” That is, every attribute of things which the phenomenon involves, must have its internal representative; and the several laws of dependence among these attributes, must be each represented by some constant relation among their representatives. This must be true of all those higher correspondences comprehended under quantitative prevision. Before the effect of any composition of causes in the environment can be exactly responded to, there must take place a parallel composition of changes in the organism—not parallel in the sense that there must be any likeness between the components of the two in complexity or sequence; but parallel in the sense that to every element or relation in the one, there must be an answering element or relation in the other. And this truth will be the more clearly realized on remembering, that if one of the elements or relations pass unrecognized, either from ignorance or mistake; or if there be any error in the reasoning or calculation—any flaw in the co-ordination; the predicted result does not agree with the real result: there is a failure in the correspondence.
These facts, while they afford a still more definite idea of that co-ordination of correspondences by which the more special and complex adjustments of the organism to its environment are effected, can scarcely fail to bring out into a yet clearer light, the general doctrine variously presented in the preceding chapters. That in these highest manifestations of Life which the culture of civilization has slowly produced—these quantitative previsions which alike imply such intense vital action, and so greatly subserve self-preservation by facilitating commerce and the arts—there should be so elaborate and complete a correspondence between the organism and the environment; serves as a crowning illustration of the truths, that life is the continuous adjustment of internal relations to external relations—the maintenance of a correspondence between them, and that the degree of life varies as the degree of correspondence. The many proofs which have been given that the life and the correspondence advance hand in hand, become doubly conclusive on finding that the two arrive at their climax together.
THE INTEGRATION OF CORRESPONDENCES.
§ 161. Yet one more point of view remains, from which the phenomena of Life must be contemplated. It requires to be observed how, out of co-ordination there grows up integration—how compound impressions, as well as the compound motions guided by them, ever more and more approximate in their apparent character to simple impressions and simple motions—how the co-ordinated elements of any stimulus or act perpetually tend towards union, so as eventually to become distinguishable only by analysis—and how, further, the connection between stimulus and act, obeying the same law, becomes constantly closer, and ends in making them two sides of the same change.
It is by virtue of this law that the higher orders of correspondence become possible. In its absence, complex impressions could not generate complex actions with the needful rapidity; nor would there be time for that immense multiplicity of correspondences which advanced life displays. If the two organic changes which constitute sensation and motion, did not, in superior creatures, follow with greater rapidity than the withdrawal of a snail into its shell follows the touch of its horn, all those correspondences with the environment which imply any quickness of adjustment, would be impracticable. And if the period that elapses between the gaze of a young child at a stranger, and the fit of crying that follows it (a period during which the component visual impressions are being co-ordinated) were habitually paralleled in the perceptions of adult life—if compound cognitions were not formed, and the appropriate operations produced by them, in periods incomparably briefer, human life would cease.
The necessity for this progressive integration of correspondences will be most clearly understood, if, regarding sensations as so many symbols, and perception as the interpretation of groups of symbols, we observe what takes place with verbal symbols and the meanings they convey: a comparison which is the more appropriate, inasmuch as the last process is but a higher form of the first. As in the lower phases of perception, a single sensation, as of scent, serves the organism as an index of the combined attributes with which such scent is connected; so, in the lower phases of language, a simple sound or sign is used to indicate a complex idea. In either case, within narrow limits, this system answers very well. But any considerable multiplication in the number of correspondences, requires another system. By scent, only some objects can be distinguished; seeing that many are scentless. Simple sounds and signs are too few in number to represent any considerable variety of ideas. Hence, in either case, a system of compound symbols becomes the prerequisite to any great extension of the correspondences. Things that are without odour, and things that are alike in odour, can be divided into sundry sub-classes, when impressions of colour and size, as well as of scent, can be appreciated. And when simple sounds are endlessly modified by articulations, and simple signs replaced by composite ones, it becomes possible verbally to indicate an infinity of objects, acts, qualities, &c. But now, what is the condition under which this more elaborate language becomes serviceable? Or, to confine the attention to one division of it:—What is required before composite written signs can supplant simple arbitrary ones? It is required that the constituent elements shall be so efficiently co-ordinated, so rapidly united in the act of perception, so integrated, as to become practically one. Had the letters that make up each word, to be separately identified, as the child identifies them when learning to read, the system would be of little or no use. Able though it might be, by the varied combinations of its elementary signs, to express with precision all words whatever; it could never compete with the limited system of simple arbitrary signs, did it remain thus cumbrous in its application. Similarly with the primordial language of the sensations. If the several colours, size, shape, motion, distance, direction of a given object, had to be successively identified by the creature perceiving it—if the object had to be spelled out in this deliberate fashion; the method of recognition by combined sensations, would yield in utility to the limited method of recognition by a single sensation. Universal in its powers, it would yet be too slow of application to satisfy the requirements. In both cases, however, the progressive integration of the component correspondences removes this difficulty, by reducing, in effect, the compound signs to simple ones. A word made up of a dozen letters, comes eventually to be recognized as instantaneously as a single letter; while the host of impressions involved in the perception of a complex object, seemingly take no more time to receive and interpret than a single sound or taste. And thus there is an infinite gain in the speciality of the correspondences, without any loss in their rapidity. Let us glance at the results under some of their leading aspects.
§ 162. After the above explanations, it needs not to dwell upon the apparent simultaneity with which the outlines, lights and shades, and all the visible peculiarities with which bodies impress us, arouse those ideas of tangible extension, of resistance, of texture, with which experience has joined them; unless to point out how truly this is an integration of correspondences—how truly the visual sensations corresponding to a certain distance, the impressions of light and shade corresponding to a certain shape, the arrangement of lines corresponding to a certain solid extension, with many others, are so united as to seem one—so united that the entire group of sensations, and the inferences drawn from them, appear to constitute but a single state of consciousness. Nor is it requisite to do more than just indicate the exceeding precision with which the most complex assemblages of these symbols are instantaneously distinguished from nearly identical assemblages; as seen in our ability to recognize by a single look, not only particular human beings, similar though they are in their chief attributes to most others, but even their particular mental states, trifling as are the outward modifications implying these. But while it is unnecessary to enlarge on these familiar facts, it may be well, for the purpose of conveying a vivid idea of the manner in which this integration of correspondences subserves the perceptions, just to describe an experiment by which its extreme strength and rapidity may be shown.
Our judgments of distance are guided by at least three separate indications. When the observed objects are known to us, the angles they subtend, or, rather, the spaces which their images cover upon the retina, aid in the estimate. The particular focal adjustments which the eyes must undergo to obtain distinct vision, and which are accompanied by certain muscular sensations, further assist. And the muscular sensations accompanying the due convergence of the visual axes, supply a third evidence. In all ordinary vision, these indications agree. But by that ingenious instrument of Professor Wheatstone's invention—the Pseudoscope—the last two are made to contradict each other. The muscular actions by which the visual axes are adjusted, being the more marked, and accompanied by the stronger sensations, give the preponderating evidence; and the result is, that when looked at through the Pseudoscope, convex objects seem concave, and concave ones convex. By particular management, however—that is, by adding to the evidence from focal adjustment some further evidence—the verdict of consciousness may be suddenly reversed. If, after contemplating the inside of a cup, and duly wondering at its apparent convexity, the cup be turned laterally little by little, so that the outside may gradually come into view, and the opening grow more elliptical; there presently arrives a time when the perception all at once changes, and the cup is seen under its ordinary aspect. Now, the fact which it here concerns us to remark as so significant, is, the impossibility of any intermediate or hesitating judgment. Notwithstanding the conflict of evidence, there is, save just at the moment of change, a quite definite perception either of concavity or convexity. The perception is not incomplete or obscure, but perfectly distinct. The preponderating impressions, by forcibly exciting all those other impressions with which they are habitually connected, produce the same effect as though these other impressions were actually received, instead of the opposite ones being received. The co-ordinated sensations have become so inseparably integrated, that none of them can be present to consciousness without the whole group to which they belong being present. The entire perception, complex as it is in nature, is shown to be practically one.
With the executive, as well as with the directive processes, this integration takes place; and may be analogously illustrated. Any long-employed combination of muscular actions—any combination of which the elements never occur in any other arrangement, eventually becomes almost undecomposable. The tricks of walk, of attitude, of manual action, into which children fall, and of which it is so difficult to break them, furnish examples. The stammering which, commencing as it often does from imitation, becomes, when once established, next to incurable, owes its pertinacity to this tendency. So, too, is it with peculiarities of handwriting. The motions of the fingers, having by years of practice with the pen been co-ordinated after a particular fashion, cannot be otherwise co-ordinated without a degree of labour to which few are equal. Though, by moving them slowly and with attention, the muscles of the fingers may be made to produce differently-formed letters; yet, on the attention being relaxed, and the usual speed resumed, they re-assume their old character. Similarly in all handicrafts, chains of perpetually-repeated muscular actions, however complex, eventually approximate in rapidity and ease, to simple motions; and, at the same time, become incapable of modified adjustment—tend more and more to produce each other automatically—grow inseparable—become integrated.
Not only between the elements of each cognition, and between the elements of each operation, does this connection grow ever more close; but also between cognitions and the operations guided by them. In the child learning to walk, or to direct its hand towards a neighbouring object, or to perform any manual act; there is a deliberate and conscious modification of the motions in obedience to the sensations. But in after-years, the various muscular adjustments by which, from minute to minute, the behests of the intellect are fulfilled, follow the will instantaneously, and without effort. While absorbed in gossip, the needle of the seamstress is carried through stitch after stitch, by a co-ordination of sensations and actions that has become next to instinctive. While deep in thought—“absent in mind,” as the phrase is—the occurrence of particular perceptions will often be quite unconsciously followed by the habitual actions appropriate to them; sometimes with ludicrous effect. The start on one side, which is produced by a loud noise close at hand; the throwing out the arms in the endeavour to regain the balance after having slipped; these and many like phenomena, show us how directive and executive processes, originally quite distinct, come to be so united, that one follows the other not only instantaneously and without volition, but often without the possibility of prevention. Even where the impressions and motions are in the highest degree complex, the law may be traced; as in the feats of a skilful billiard-player. In one of his strokes, we see the distance, direction, relative positions of the balls to each other, to the cushions, and to the pockets, all united into a complex visual impression co-ordinated with the greatest nicety; we see the direction of the cue, its adjustment to the ball, the strength of its impact, and the quality of its impact, all accurately modified to suit the requirements; and we see that by long habit, the compound impression has been so united with the compound action, that the one follows the other almost mechanically. No reasoning or calculation is required; or, indeed, is permissible. For it is notorious that in this, and like games of skill, any lengthened consideration, any hesitation, any anxiety, any active interference on the part of the higher mental faculties, almost inevitably causes a failure. The direct relation that has been established between the constituent sensations and motions, must be allowed free play; and success becomes sure in proportion as, by constant co-ordination, the combined changes have become practically one change.
In all which instances of the gradual consolidation of the elements of any habitual correspondence, we may perceive how that automatic character displayed in the simple correspondences of inferior creatures, tends to be gradually assumed by more complex correspondences—how that integration, which the reflex and purely instinctive correspondences perfectly exemplify, is partially exemplified by all higher correspondences, in the order of their ascending complication.
§ 163. But it is not only to the constituents of immediate perception, to the elements of composite motion, and to the combination of the two, that this law applies; it applies also to the highest processes of cognition. The most advanced abstractions of science, display it equally with the acquirement of manipulatory skill, or the power rapidly to recognize objects. For the act of making a generalization, is, in reality, an integration of the various separate cognitions which the generalization includes—is a union of them into a single cognition. After there has been a mental accumulation of phenomena presenting a certain community of nature—remembered first as isolated facts, and after further experience colligated as facts having some resemblance—there suddenly, on the occurrence perhaps of some typical example, arises a cognition of the relation of coexistence or sequence common to the whole group: the particular facts, before but loosely aggregated, all at once crystallize into a general fact—are integrated. The mode, too, in which this result is brought about, is the same in these highest as in the lowest cases. As that continuous repetition of experiences in which any two sensations are always joined, any two muscular contractions constantly performed together, or any perception uniformly followed by a special motion, results in the greater or less integration of the component changes; so, the continuous repetition of those more complex experiences, which, though superficially unlike, one and all present the same fundamental relation of coexistence or sequence, ultimately results in establishing a union in thought between the elements of this relation: and this union, made ever stronger by still multiplying experiences, constitutes the generalization of them. Moreover, it will be obvious without details, that the same thing holds respecting the generalization of generalizations. Thus, the integration of correspondences is traceable from the simplest up to the most elaborate of the intellectual processes. And in the last, as in the first, the effect is so to simplify the complex directive and executive actions, as to render practicable, adjustments that would else fail from the elaborateness and slowness of the processes they involved. For as the perception of a complex object would mostly fail of its end, if it could be effected only by slowly spelling out the constituent sensations produced; so, any series of compound experiences, which, embodied into a generalization, afford valuable guidance, would be of little or no service if every member of the series had to be separately recollected before the guiding cognition could be formed.
§ 164. This gradual union of the elements of any internal change by which the organism adapts itself to an external coexistence or sequence—this process which may be almost described as the development of a special faculty for each special relation—has been, in common with previous ones, abundantly displayed in the course of human advancement. Being a process through which only, highly special and complex correspondence can be achieved, progress in integration has been a necessary accompaniment of progress in speciality and complexity; and in proportion as civilization has displayed the last, it must have displayed the first. The one having been illustrated in detail, it is therefore needless to illustrate the other. Similarly, greater length and degree of life, involved as they are by greater complexity and speciality of correspondence, have accompanied that greater integration which has rendered these possible.
THE CORRESPONDENCES IN THEIR TOTALITY.
§ 165. Thus then we find variously illustrated in detail, the truth enunciated at the outset, that all vital phenomena are directly or indirectly in correspondence with phenomena in the environment. Whether the kind of Life contemplated be that embraced by Physiology, or that of which Psychology treats, it equally consists of internal changes that mediately or immediately conform to external coexistences and sequences. The assimilative processes going on in a plant, and the reasonings by which a man of science makes a discovery, alike exhibit the adjustment of inner relations to outer relations. That method by which we sought out the fundamental fact on which to base a Synthetic Psychology, is justified by its results. By comparing the phenomena of mind with the most nearly allied group of phenomena—those of bodily life—and inquiring what is common to both groups, a generalization was disclosed which we find on examination really does express the essential character of all mental actions. Regarded as they have been in the foregoing chapters, under every variety of aspect, the manifestations of intelligence are universally found to consist in the establishment of correspondences between relations in the organism and relations in the environment; and the entire development of intelligence is seen to be nothing else than the progress of such correspondences in Space, in Time, in Speciality, in Generality, in Complexity.
As hinted on more than one occasion, these various modes in which the advance of the correspondence displays itself, are but so many different aspects of one mode. The vast array of phenomena which, for convenience' sake, we have considered under separate heads, form, in reality, one general, continuous, and inseparable evolution. The various orders of progress described, have not only been going on simultaneously, but have severally rendered each other possible. Each particular kind of advance has opened the way for advances of other kinds; and these again have reacted in like manner. All have been furthered by each: each has been furthered by all. Not only is it, as we saw, that the extension of the correspondence in Time, is at first rendered possible only by its extension in Space; but it is that ultimately, as in the researches of astronomers, its greatest extension in Space is achieved through its extension in Time. Not only is it that the progress of the correspondence in Time and Space involves an increase in its speciality; but it is that eventually, that immense increase in speciality implied by the making of telescopes and chronometers, gives a new progress to the correspondence in Time and Space. On the one hand, that advance in the complexity of the correspondence, which is seen in the ability to discriminate between objects that have many attributes in common, amounts to an advance in its speciality; and on the other hand, it is only through an advance in speciality, that greater complexity of correspondence can be reached. While, by the correspondence to higher and higher generalities, the way is opened for more complex and more special correspondences; it is only by accumulated experiences of such more complex and more special correspondences, that the correspondence to still higher generalities becomes possible. At both extremes of the evolution, this consensus among the various orders of correspondence is clearly traceable: the only difference being, that the further the development advances, the more intimate does the consensus become. If we contemplate the results of improved vision in some lowly member of the animal kingdom, we see that in addition to bringing within view a wider range of objects, and so extending the correspondence in Space; and in addition to giving earlier notice of the approach of prey or enemies, and so extending the correspondence in Time; it entails a greater power discriminating among near objects, and so makes possible, correspondences of higher speciality. And if we consider what takes place in the man of science, from the adjustment of a further inner relation to some further outer relation—say the relation between an electric current and the magnetization of iron—we see, that while itself an advance in speciality of correspondence, it immediately leads to a great variety of advances in all orders of correspondence. By multiplication of experiments, it forthwith leads to a progress of the correspondence in generality—leads to an internal generalization corresponding to the general relation existing externally. It makes possible other generalities and specialities of correspondence to the phenomena of terrestrial magnetism. By disclosing the galvanometer, it not only establishes adjustments, both general and special, between inner relations and the outer relations subsisting among electrical phenomena of various orders; and not only does the same thing in respect to an immense range of chemical phenomena; but, through inquiries like those of Du Bois Reymond, it brings within range some of the phenomena of nervous and muscular action. Through the agency of the electric telegraph, which has also grown out of it, it makes possible, hosts of special correspondences between men's actions and the changes occurring at remote points on the earth's surface; it enables astronomers to ascertain the relative longitudes of observatories with the greatest nicety; and by supplying them with an improved means of registering meridional transits, it gives better data for calculating the distances and motions of the stars, for determining the structure of the nebula to which we belong, for ascertaining the motion of the sun in space, and for developing the grandest astronomical generalizations. These are but a few of the instances in which this one advance of the correspondence has facilitated other advances, of all orders and in all directions; and, in a greater or less degree, the same results happen from every other advance
Thus, it will be manifest, that from the lowest to the highest forms of life, the increasing adjustment of inner to outer relations, is, if rightly understood, one indivisible progression. Just as, out of the homogeneous tissue with which every organism commences, there arises by one continuous process of differentiation and integration, a congeries of organs performing separate functions, but which remain throughout mutually dependent, and indeed grow more mutually dependent; so, the correspondence between the phenomena going on inside of the organism and those going on outside of it, beginning, as it does, with some simple homogeneous correspondence between internal and external affinities, gradually becomes differentiated into various orders of correspondences, which are constantly more and more subdivided, but which nevertheless maintain a reciprocity of aid that grows ever greater as the progression advances. The two progressions are in truth parts of the same progression. Not to dwell upon the facts which imply that the primordial tissue is endowed throughout with the several forms of irritability in which the senses originate, and that the organs of sense arise, like all other organs, by the differentiation of this primordial tissue; not to dwell upon the fact that the impressions received by these senses form the raw materials of intelligence, which arises by combination of them, and must therefore conform to their law of evolution; not to dwell upon the fact that intelligence advances pari passu with the advance of the nervous system, and that the nervous system obeys the same law of development as the other systems; not to dwell upon these facts, it is sufficiently manifest, that as the progress of organization and the progress of the correspondence between the organism and its environment, are but different aspects of the evolution of Life in general, they cannot fail to harmonize. And hence, in this organization of experiences which we call Intelligence, there must be that same continuity, that same subdivision of function, that same mutual dependence, and that same ever-advancing consensus, which characterize the physical organization. The correspondence between the organism and its environment, while becoming in each higher phase more specialized and heterogeneous, must ever remain, as it has been from the beginning, one and indivisible.
§ 166. We find then, that whether, as in preceding chapters, the facts are examined in detail, or whether, as here, they are contemplated in their ensemble, they necessitate the conclusion that, fundamentally considered, Intelligence has neither distinct grades, nor is constituted of faculties that are truly independent; but that its highest phenomena are the effects of a complication that has arisen by insensible steps out of the simplest elements. Every form of Intelligence being, in essence, an adjustment of inner to outer relations; it results that as, in the advance of this adjustment, the outer relations increase in number, in complexity, in heterogeneity, by degrees that cannot be marked; there can be no valid demarcations between the successive phases of Intelligence. The space through which the correspondence gradually extends, has no definite boundary up to which a certain order of mind is competent, but beyond which another order is required. No precise length of time can be named, as the greatest to which the actions can be adjusted by one supposed species of guiding principle. Among the degrees of speciality in the correspondence, it is impossible to fix on that which can be reached, but not passed, by any denomination of mental endowment. And similarly under whatever aspect the phenomena are regarded. Evidently then, the classifications current in our philosophies of the mind, can be but superficially true. Instinct, Reason, Perception, Conception, Memory, Imagination, Feeling, Will, &c., &c., can be nothing more than either conventional groupings of the correspondences; or subordinate divisions among the various operations which are instrumental in effecting the correspondences. However widely contrasted they may seem, these various forms of intelligence cannot be anything else than either particular modes in which the adjustment of inner to outer relations is achieved; or particular parts of the process of adjustment. It is doubtless true that there are perceivable distinctions between the phenomena grouped under these different heads. But when considered in their essentials, it becomes manifest that, as contemplated from one point of view, they merge into each other as branches into one trunk; and that, as contemplated from another point of view, they are but the different constituents of which each more complex correspondence is made up. All the facts are comprehended under the generalization that has been enunciated. The entire range of phenomena which Psychology embraces, comes within this formula which unites them with those of Physiology.
§ 167. Nevertheless, as the two kinds of Life treated of under the respective heads of Physiology and Psychology, though primordially the same, are yet in their general aspects widely unlike; it behoves us to inquire whence arise the differences between them. The various modes of intelligence known as Instinct, Memory, Reason, Feeling, Will, and the rest, having, in spite of their community of nature, specific distinctions; it remains to be determined in what these consist. If, as above alleged, the several grades of mind, and its component faculties, are phases of the correspondence; they can be interpreted as such: and to complete the argument it is needful that they should be so interpreted. We have now, then, to enter upon another department of our subject. Closing here the General Synthesis, and carrying with us the fundamental truth evolved by it, it remains to found upon that fundamental truth a Special Synthesis.
[∗]See Galton's account of the Damaras.
[†]Dr. Whately for example.
[∗]See Westminster Review for April, 1852.—Art. IV. “A Theory of Population.”
[∗]For explanation, see the before-mentioned essay on “The Genesis of Science.”
[∗]See Proceedings of the Ethnological Society.