Front Page Titles (by Subject) CHAPTER III.: PROXIMATE DEFINITION OF LIFE. - The Principles of Psychology
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CHAPTER III.: PROXIMATE DEFINITION OF LIFE. - Herbert Spencer, The Principles of Psychology 
The Principles of Psychology (London: Longman, Brown, Green and Longmans, 1855).
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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.
[∗]See Westminster Review for April, 1852.—Art. IV. “A Theory of Population.”