Front Page Titles (by Subject) CHAPTER II.: THE LAW OF INTELLIGENCE. - The Principles of Psychology
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CHAPTER II.: THE LAW OF INTELLIGENCE. - Herbert Spencer, The Principles of Psychology 
The Principles of Psychology (London: Longman, Brown, Green and Longmans, 1855).
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THE LAW OF INTELLIGENCE.
§ 173. All Life, whether physical or psychical, being the combination of changes in correspondence with external coexistences and sequences; it results, that if the changes constituting psychical life, or intelligence, occur in succession, the law of their succession must be the law of their correspondence. That particular kind of Life which we distinguish as intelligence, including as it does the various developments of the correspondence in Space, in Time, in Speciality, in Complexity, &c.; it necessarily follows that the changes of which this intelligence consists, must, in their general mode of co-ordination, harmonize with the co-ordination of phenomena in the environment. The life is the correspondence; the progress of the life is the progress of the correspondence; the cessation of the life is the cessation of the correspondence: and hence, if there is one particular department of the life, which, more manifestly than any other, consists in the constant maintenance of the correspondence; the changes which make up this highest department of life, must, more manifestly than any other, display the correspondence. The fundamental condition of vitality, is, that the internal order shall be continually adjusted to the external order. If the internal order is altogether unrelated to the external order, there can be no adaptation between the actions going on in the organism and those going on in its environment: and life becomes impossible. If the relation of the internal order to the external order, is one of but partial adjustment; the adaptation of inner to outer actions is imperfect: and the life is proportionately low and brief. If, between the inner and the outer order, the adjustment is complete; the adaptation is complete: and the life is proportionately high and prolonged. Necessarily, then, the order of the states of consciousness is in correspondence with the order of phenomena in the environment. This is an à priori condition of intelligence.
Clear, however, as it is, that from this à priori condition of intelligence, must result the law of succession of psychical changes, an adequate expression of such law is by no means easy to find. Did the phenomena in the environment form, like the phenomena of consciousness, a succession; there would be no difficulty. The entire fact would be expressed by saying that the internal succession parallels the external succession. But the environment contains a great number of successions of phenomena, going on simultaneously. Further, the environment contains a great variety of phenomena that are not successive at all, but coexistent. Yet again, the environment is unlimited in extent, and the phenomena it contains are not only infinite in number, but insensibly pass into a relative non-existence, as the distance from the organism increases. And yet once more, the environment, relatively considered, is ever varying as the organism moves from place to place in it. How, then, can the succession of psychical changes be in any way formulated? How is it possible to express the law of a single series of internal phenomena, in terms of its correspondence with an infinity of external phenomena, both serial and non-serial, mixed in the most heterogeneous manner, and presented to the moving organism in an endless variety of fortuitous combinations?
Were it not that the inner relations must be in correspondence with the outer ones; and that therefore the order of the states of consciousness must be in some way expressible in terms of the external order; we might almost despair of finding any general law of psychical changes. Even as it is, we may be certain that any such general law cannot apply to extended portions of the series of changes. Dependent as these must in great measure be, upon the heterogeneous combinations of phenomena by which the organism is at any moment environed, and upon the new heterogeneous combinations perpetually disclosed by its movements, they can be no more formulated than the heterogeneous combinations of external phenomena can be formulated. Evidently, therefore, it must be in the constituent changes, and small groups of changes, rather than in the longer concatenations of changes, that we must look for a law.
And this is the indication given by certain still more general considerations. As on each particular link in a chain, depend the succeeding links; so, on each particular change in consciousness, depend all the succeeding changes: and hence the law of the succession of changes, must be really involved in the law of the individual change. If there occurs in consciousness a change from state A to state F, there will follow certain changes F to L, L to D, D to K, &c.; but if the first change had been from A to D, some other series of changes, D to J, J to C, C to N, would have resulted. So that, as the particular combination of subsequent changes is ever dependent upon the change occurring at each moment; and as each of these subsequent changes becomes, when it occurs, the change on which those succeeding it depend; it follows that the law of the individual change is the sole thing to be determined.
Not simply, therefore, as being the only phenomenon in the mental succession which there is any hope of formulating; but as being the phenomenon on which all other phenomena in the mental succession must hinge; the subject of our inquiry must be—the law of the connection between any two successive states of consciousness—the law of the elementary psychical change.
§ 174. Using the expression state of consciousness, in its most extended sense, as meaning the psychical state of any order of creature, and also as meaning any species of psychical state, from the most simple to the most complex; the law of the connection between any two successive states of consciousness, will become manifest on considering the à priori necessity to which it must conform. Each of the two states originally answers to some particular phenomenon external to consciousness. Every external phenomenon exists in certain relations to other phenomena. Hence, a correspondence between the internal order and the external order, implies that the relation between any two states of consciousness, corresponds with the relation between the two external phenomena producing them. How corresponds? The two states of consciousness occur in succession: and all successions are alike in so far as they are simply successions. In what, then, can the correspondence consist? It consists in this; that the persistency of the connection between the two states of consciousness, is proportionate to the persistency of the connection between the phenomena to which they answer. The relations between external phenomena are of all grades, from the absolutely necessary to the purely fortuitous. The relations between the answering states of consciousness must similarly be of all grades, from the absolutely necessary to the purely fortuitous. And as the correspondence becomes more complete, that is—as the intelligence becomes higher, the various grades of the one must be more and more accurately paralleled by those of the other. When any state a occurs, the tendency of some other state d, to follow it, must be strong or weak according to the degree of persistency with which A and D (the objects or attributes that produce a and d) occur together in the environment. If, in the environment, there is a more persistent occurrence of A with B than of A with D; then, the maintenance of the correspondence implies, that when a arises in consciousness, b shall follow rather than d. If there are in the environment a great variety of things in connection with which A occurs; then, when the state of consciousness a, arises, it must be followed by the state of consciousness answering to the thing most generally occurring along with A. These are manifest necessities. If the strengths of the connections between the internal states, are not proportionate to the persistencies of the relations between the answering external phenomena; there must be a failure of the correspondence—the inner order must disagree with the outer order. Psychical life, in common with life in general, being the continuous adjustment of inner to outer relations; and the occurrence of any relation between states of consciousness, being, in itself, nothing else than an exhibition of the fact, that the cohesion of the antecedent and consequent states was greater than the cohesion between the antecedent state and any other state; it follows inevitably, that, to effect the adjustment, the cohesion of the states must vary as the cohesion of the phenomena represented by them. The law of intelligence, therefore, is, that the strength of the tendency which the antecedent of any psychical change has to be followed by its consequent, is proportionate to the persistency of the union between the external things they symbolize.
To say, however, that this is the law of intelligence, is by no means to say that it is conformed to by any intelligence with which we are acquainted. It is the law of intelligence in the abstract; and is conformed to by existing intelligences in degrees more or less imperfect. To the extent that psychical changes fulfil this law, to such extent only do they constitute intelligence; and it is but very incompletely that even the highest orders of psychical changes do this. A due understanding of the matter will, however, be best obtained, by examining the several objections to this general statement which suggest themselves.
§ 175. Beyond doubt, if we contemplate the acts of the animal creation in general, we find endless instances in which the internal order entirely fails to parallel the external order. It is clear that in a moth which flies at the candle-flame, there exists no relation of psychical states answering to the relation between light and heat in the environment. The relation between the odour of a flower and the contained honey, is duly responded to by sequent actions in the moth; as is also the relation between a certain change in the visual field, and the approach of a living body. But there is no internal adjustment by which, after the visual impression produced by a flame, anything analogous to the feeling of a burn is suggested; and hence the creature's death. Again, the birds which, on uninhabited islands, allow explorers to approach close to them, manifestly lack that co-ordination of psychical changes by which the birds of our woods and moors are led to fly the sportsman. Externally, there coexists with particular visible appearances, a destructive activity; but internally, the state of consciousness produced by these visible appearances, is not followed by any state of consciousness representing a destructive activity: and a risk of being killed is the consequence. In the mind of a child, the state produced by the sight of some brightly-coloured berry, does not suggest any state representative of pain, or of the word “poison;” but more probably, some representation of a pleasant taste; and should certain injurious chemical properties coexist with these attractive visible ones, the child's life may be endangered. But in all cases of this kind, in which the order of psychical changes is totally at variance with the order of external phenomena, what is the implication? Do we not speak of them as resulting from lack of sagacity? or as evincing ignorance? And is it not a corollary, that as the non-conformity of the inner to the outer order is want of intelligence, the conformity of the inner to the outer order is that in which intelligence, abstractedly considered, consists?
Yet more manifest will the truth of this conclusion become, if we look at a few instances in which the failure of the correspondence is not total, but partial. In the great majority of cases, the dog that comes on hearing his name called, does so in the expectation of finding his master, or some member of the family; but if, as occasionally happens, his name is called by a stranger, the sequence in his states of consciousness, and his consequent actions, are not adapted to the external facts; or, as we say, he makes a mistake. Among the Australian savages, who, in their natural state, mostly meet with violent deaths, it is the belief that any one who dies without a visible cause has been killed by an unseen enemy; and a stranger who happens to be found near at hand, runs a great risk of being sacrificed as the supposed assassin. Here, though the mental succession very generally agrees with the succession of phenomena in the environment, it by no means uniformly does so. The Laplanders again, finding, as they do, a constant relation between hot weather and the continuance of the sun above the horizon during the night, doubtless have an established connection in thought between these phenomena—a connection which, however completely it may answer to the external connection in that limited part of the environment known to them, does not answer to the ordinary external connection. The earlier chemists, in virtue of a large number of experiences respecting the combinations of acids and bases, came habitually to think of substances that neutralized bases, as substances having sour tastes; but this sequence of the ideas—ability to neutralize a base, and the possession of a sour taste—though very generally in harmony with external relations, is not so in all cases.
What, now, are the terms we use respecting instances like these, in which the inner order does not completely answer to the outer order? We regard them as indicating a low degree of intellect; or as showing a limited experience; or as the results of but a partial enlightenment. And the disappearance of these discrepancies between thoughts and facts, we regard as an advance of intelligence.
It is abundantly clear, then, that to whatever extent the order of psychical changes does not conform to the order of the environing phenomena, to that extent there is a lack of intelligence. And hence it follows, that the law in the fulfilment of which the conformity consists, may properly be called the law of intelligence.
§ 176. The greatest apparent obstacle to the establishment of this law, is that presented by the phenomena of coexistence. In so far as the environment presents motions and changes, there is no difficulty in understanding it to be the law of intelligence, that the strength of the tendency which the antecedent of any psychical change has to be followed by its consequent is proportionate to the persistency of the union between the external things they symbolize. But when the union between the external things they symbolize is not a union of successive phenomena, but a union of simultaneous phenomena—not a union in Time, but a union in Space—not a sequence, but a coexistence; then, it becomes less easy to see how the parallelism between the inner and the outer order can result from the fulfilment of this law. The connection between two states of consciousness occurring in succession, can very well represent the connection between two external phenomena occurring in succession. But if it can do this, it cannot also represent the connection between two external phenomena not occurring in succession. Whence it follows, that in so far as environing coexistences are concerned, the correspondence cannot be effected by any change in consciousness conforming to the alleged law of intelligence.
The reply to this objection is, by implication, contained in a foregoing chapter, on “The Relations of Coexistence and Non-Coexistence.” It is there shown, à posteriori, that the relation of coexistence is known as a doubled sequence—a sequence whose terms follow one another through consciousness in either order, with equal facility and vividness; and it is pointed out that, even à priori, we might conclude, that as consciousness can exist only by a succession of changes, an external no-change can be presented in consciousness only by a change that is immediately reversed—only by a progression that is instantly followed by an equivalent retrogression—only by a duplication in consciousness, made up of a sequence and its inversion. Such being the nature of the relation of coexistence, subjectively considered, the law of intelligence as above formulated, applies to it as fully as to the relation of sequence. If any two phenomena, A and B, habitually coexist in the environment; then, when the phenomenon A is presented to the senses, the induced state of consciousness, a, is immediately succeeded by the state b, representing the phenomenon B. The process of thought does not end here, however: if it did, the external relation would be known as a sequence. But the phenomenon B, in the environment, being as much the antecedent of A as A is of B (neither of them ever being either antecedent or consequent, otherwise than in the order of our experience of them), it results that the state b having been induced, the law involves that it shall be followed by the state a. The state a again induces the state b, and is itself once more re-induced; and so on, as long as the relation remains the object of thought. To render the matter the clearer, let us take a case. If, in the light, the visible outlines and colours of a body are presented, the resulting state of consciousness is instantly followed by the consciousness of something resistant; and conversely, if, in the dark, a body is touched, the resulting state of consciousness is instantly followed by the consciousness of something extended. But in neither case is this all. When the consciousness of resistance has suggested that of extension, the consciousness of extension is not followed by some third consciousness of another kind. Were it so, the object would cease to be thought of. But, as we all know, when the idea of extension has been suggested, that of resistance does not finally disappear; nor when the idea of resistance has been suggested, does that of extension finally disappear. Both continue to be thought of, as it would seem, almost simultaneously. And seeing that the two terms of the relation, extension and resistance, cannot be cognized in absolutely the same state of consciousness; seeing, further, that the persistent consciousness of them cannot be one state of consciousness, which is equivalent to no consciousness; it follows, that the apparently incessant presentation of both, is really a rapid alternation—an alternation so rapid as to produce the effect of continuity: just as the alternating light and darkness to which each part of the retina is subjected while watching a torch whirled round, produce the impression of a circle of fire; or just as the alternations experienced by the ear-drum, when receiving a succession of separate pulses, constitute a uniform sensation of sound. And, indeed, these considerations render it sufficiently clear, that only in virtue of the law of intelligence as above formulated, does the relation of coexistence become cognizable. For this great rapidity with which the two states of consciousness, answering to two coexistent phenomena, continually reproduce each other, itself exemplifies the extreme cohesion of those internal states which correspond to extremely coherent external phenomena. And it is in consequence of this extreme cohesion, and the rapid alternation involved by it, that the two phenomena are presented apparently together, and the idea of coexistence generated.
When it is further remarked, that where, as in most cases, there are not two coexistent phenomena but a group, this same law implies a like cohesion of a number of different states of consciousness, which must similarly produce and reproduce each other in all orders; and when it is remarked that such an irregularly varied presentation and representation of combined properties, is just what we know takes place, the conformity of the facts to the alleged law will be rendered yet more apparent. And even still more apparent will it become on remembering, that whereas such of the states of consciousness as answer to invariably coexistent phenomena, as resistance and extension, continue reproducing each other during the whole perception, forming, as it were, the basis of it; the several other states of consciousness answering to the special qualities of the object—qualities not invariably coexisting with resistance and extension—do not remain thus persistent, but appear, and disappear, and reappear in consciousness, with degrees of frequency varying more or less according to the constancy of the answering qualities.
§ 177. A fact which at first sight may be thought to conflict with the generalization to be established, is, that a great proportion of the changes in consciousness arise after a fashion that is in one sense fortuitous. A succession of noises heard through the open window, traverses consciousness in a totally irregular manner, of which no account can be given beyond describing it. When walking through the streets, the passing people and vehicles produce internal changes of which the succession is indeterminate. Though, on receiving certain visual impressions, there result in the mind the changes constituting the perception of a man; and though, in so far, the order of the changes is determinate; yet, the occurrence of these impressions and the consequent perception, the moment after there had arisen some thought concerning the weather or the last news, is a fact which would appear unconformable to any law of psychical changes. Moreover, it may be objected, that not only are very many of the changes which occur in the state of consciousness from minute to minute, accidental, but that the order of the series of states, even in some of its largest features, is accidental. A mere chance may determine a man to go abroad or remain at home; to commence a new occupation, or continue an old one; to marry, or remain a bachelor; and the character of the whole series of his subsequent states of consciousness may thus be modified. Nor is it only of the changes constituting the human consciousness that this is true: it is more or less true of all grades of psychical changes. No matter what the degree of its intelligence, every creature is subject to impressions between which no internal law of connection can be traced. And hence, to a large part of the successive changes of which intelligence in general consists, the formula above given would seem to be inapplicable.
This difficulty, insurmountable as it looks, will disappear when the formula is interpreted in its most general sense; and it will be perceived that these, in one respect, fortuitous changes, really conform to the law of intelligence. The law is, that the strength of the tendency which the antecedent of any psychical change has to be followed by its consequent, is proportionate to the persistency of the union between the external things they symbolize. Thus far, we have considered this law with more especial reference to those connections in consciousness which correspond to established connections in the environment: we have dealt with it as a generalization of the facts commonly grouped under the head of “association of ideas.” Here, however, the connections in the environment to which the connections in consciousness correspond, are not established connections, but accidental ones. A fortuitous relation in the environment, is paralleled by a fortuitous relation in thought. Two adjacent states of consciousness answer to two phenomena that are adjacent in Space or Time. Thus far the law manifestly applies as before. The internal order conforms to the external order. But how, it may be asked, can the tendency of the antecedent state of consciousness to be followed by the consequent state, be described as proportionate to the persistency of the union between the external things they symbolize? Very properly. Suppose the relation in the environment to be that between a certain individual and some unusual place at which he is met. This relation may either be considered generally, in connection with our average experiences; or specially, as a particular experience. Generally considered, the relation is one whose terms have no persistency of union whatever; seeing that this individual may never have been in that place before, and may never be in it again: and in conformity with this total absence of persistency in the external union, is the total absence of any general tendency for the consciousness of that individual and the consciousness of that place, to follow one another—at any rate before he was met there. Specially considered, the relation is one that actually occurred; and when it occurred, the union between its terms was absolute—there was for the time being an absolutely persistent union between the place and the person—a union that was absolutely persistent in the sense that for the moment it was indissoluble, and its occurrence thenceforth became an unalterable fact: and in conformity with this temporarily absolute coexistence, is the temporarily absolute tendency of the answering states of consciousness to follow one another. As, for the time being, the adjacent coexistence was as absolute as that of extension and resistance; so, for the time being, the cohesion between the two states of consciousness was as absolute as that between the conceptions of extension and resistance. And as, generally, there is no such adjacent coexistence; so, generally, there is no such tendency for the two states of consciousness to occur in juxtaposition. Thus, rightly interpreted, the law applies as fully to the relations presented in any act of perception, even when they are fortuitous, as it does to those relations which an accumulated experience establishes among the ideas.
§ 178. In the succession of psychical changes, there doubtless occur many combinations which are not readily to be accounted for on the hypothesis that the strength of the tendency which the antecedent of any psychical change has to be followed by its consequent, is proportionate to the persistency of the union between the external things they symbolize. Thus, respecting the case last instanced, it may be remarked, that though before a certain person has been met in a certain place, there exists no tendency whatever for the states of consciousness answering to the place and the person to occur together; yet, afterwards, there will often be a very decided tendency for one of the states to call up the other—a tendency so decided that it may show itself on many successive occasions. Whence it would appear, that in such cases, a more persistent relation is established between the states of consciousness than existed between corresponding phenomena. Moreover it is observable, that in many cases, the extremely exceptional character of the external relation, becomes the very cause of tenacity in the internal relation: the more astonishing the event—the more utterly it is at variance with the ordinary course of nature, the stronger becomes the cohesion between the answering states of consciousness. Whence it would appear that in some instances, psychical changes obey a law the very reverse of that enunciated. And again, it may be asked, how, if the law is as alleged, can consciousness ever escape out of certain indissolubly related states when once it gets into them? If, for instance, the necessary relation of coexistence between extension and resistance, is known through the rapid alternation of the states of consciousness answering to them; if these states are as inseparable in the organism as the phenomena in the environment; and if there is no other state so closely coherent to either as each is to the other; why should not the two go on reproducing each other for ever?
Fully to answer these and all like queries, would be to include in this chapter an entire system of psychology; seeing that when all the peculiarities of the succession of psychical changes are explained, everything is explained. Here none but general replies can be given. Of these the first is, that, as already said, the law enunciated is the law of intelligence in the abstract; not the law of our intelligence, or of any intelligence with which we are acquainted. It is the law to which psychical changes tend more and more completely to conform, as the intelligence becomes higher; but which can be perfectly conformed to only by a perfect intelligence. And a little consideration of the anomalies will render it manifest, that many of them imply nothing beyond imperfection in the conformity. But in the great majority of cases, it will, I believe, be found, that what seem to be nonconformities, are really conformities of a complex kind. It must be remembered that the succession of any one state of consciousness after any other, is the result, not of any single tendency, but of a combination of tendencies. As, in the environment, each phenomenon stands related not to one other, but to many others; as the relations in which it stands to these many others are some of them necessary, some very general, some special, some purely fortuitous; it follows that in fulfilment of the law of intelligence, each state of consciousness has connections, more or less close, with many other states—has a number of other states simultaneously tending with various degrees of strength, to arise after it. The consequence is, that the change which actually takes place, is the resultant of many tendencies acting together. The new state of consciousness produced, is produced by a composition of forces. The particular force with which the new state cohered to its antecedent, is aided by the forces with which a group of allied states cohered to it; and by the union of a number of small forces, a tendency may be produced which overcomes some single tendency much stronger than any one or two of them. It is just as with the great physical law of the external world. Simple as is the principle that every atom of matter attracts every other with a force varying inversely as the square of the distance; yet, we see in the still unsolved “problem of three bodies,” how complex becomes the effect when several forces are in action; and how, when a number of bodies are involved, the course that will be pursued by any one of them becomes altogether incalculable. Similarly, though the law of attraction of mental states is simple; yet, when the attractions of a number of mental states are operating at the same moment—some uniting, some conflicting—it becomes next to impossible to determine the specific result. And just as in the ascent of a balloon, we may meet with a phenomenon seemingly quite at variance with the law of gravitation, though really quite in harmony with it; so, there may occur mental changes which, while they appear to be directly opposed to the law of psychical succession, are nevertheless fulfilments of it.
Joining with this general explanation of minor anomalies, the previous interpretations of the law in its leading applications, it can no longer be doubted that the strength of the tendency which the antecedent of any psychical change has to be followed by its consequent, is proportionate to the persistency of the union between the external things they symbolize. This is the à priori necessity: and this is the generalization reached à posteriori. Only in virtue of this law can there be that adjustment of internal to external relations, without which life is impossible: and only on the supposition of such a law can we explain the facts, that relations which are absolute in the environment are absolute in us; that relations which are probable in the environment are probable in us; that relations which are fortuitous in the environment are fortuitous in us. Unquestionably, therefore, this law is the law of intelligence.