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in our own day, attribute to heredity so important a part in the formation of instincts, that they cannot be passed by in silence. Indeed, according to these theories, heredity is one of the essential factors of psychological development; and so mighty and supreme is its influence, that it not only preserves instincts, but also creates them. Hence we are obliged to study more closely the nature of instinct, and to abandon the domain of facts, in order to enter into that of causes, that is, of hypotheses. This is to be regretted, for it is no trifling thing to attempt cursorily a theory of instinct. To us it seems that there is not in the whole field of psychology a more intricate question than this; and Schelling did not at all exaggerate when he said, 'For the thinker there are no phenomena more important than the phenomena of animal instinct, nor is there any better criterion of true philosophy.'

We will restrict our brief inquiry into this subject to two questions-What is instinct? and, What is its origin?

To the first question we reply: Instinct is an unconscious mode of intelligence. To the second: It is possible that instincts are only habits fixed by heredity.

It cannot be denied that it is only within the past hundred years that instinct has been seriously studied. The present century especially has done much. In past times we find only confused views and ingenious paradoxes: but naturalists have now removed the question to its proper sphere, that of observation and experiment. But when we study instinct from the naturalist's standpoint, the first thing that strikes us is the perfect adaptation of organs to instinct. 'An animal's form corresponds perfectly with its habits; it desires only what it can attain by means of its organs, and its organs do not incite it to anything for which it has not a propensity. The mole, destined by its needs to live underground, has in its organs nothing that would lead it aside from that disposition. Although it can see, still its sight lacks precision, because its eyes are small, and surrounded by a close growth of hairs. Its fore-paws are altogether organized for burrowing, not for walking. The paw is so formed and so related to the fore-arm, that it can hardly be used for locomotion without delving. The sloth, which walks upon the outer edge of the feet with the toes doubled in, is extremely tardy of movement on level

ground, a circumstance which gave rise to the erroneous idea that nature's treatment of the animal had been that of a stepmother. But this is not the case: the sloth is as perfect in its kind as all other animals; its limbs are so arranged as to enable it to climb, and to live in trees. The spider's legs are so arranged and organized that it moves with difficulty over a plane surface: these organs are intended for use on a line or a thread, and the spider carries about the materials from which to spin such thread.1 In general we might say: As is the organism, so are the instincts; and vice versâ. Given the instincts of an animal, a good naturalist can infer its organization; or, given its organization, he can infer its instincts.

This intimate correlation between the physiological and the mental constitution leads naturally to the conclusion that the instincts of an animal result from its organization. Each organ, even each tissue, has its special function to discharge, and this tendency to the discharge of functions constitutes the need or instinct; the same organ or the same tissue communicates to the being in which it exists this same need; each additional organ or tissue adds a new need or instinct. Hence the instinct of an animal is the sum of the instincts of its various organs; it is their necessaryy—their inevitable consequence, and it comes into play under influences to which the animal is unconsciously subject.

This explanation is simple enough, but may not be perfectly sound. It is certain that instinct depends on organization, but it is very questionable whether it results exclusively from it. This is a region where the phenomena are so complex that physiology is insufficient to explain them all, for here evidently occurs the mysterious transition from the purely organic to the mental life, by means of reflex action, which is principally physiological, and of instinct, which is principally psychological. This transition is

insensible and incomprehensible, and serves well to show that any line of demarcation drawn between psychology and physiology is arbitrary, and that mental life is slowly and gradually disengaged from physical life, so that it is impossible to tell where or how it has its rise. Neither can mechanism-which seems to be the

1 Müller, Physiologie, ii. 108.

ultimate, the irresolvable character of all vital phenomena-prove sufficient to explain instinct. For if mechanism explains the lower forms of spiritual life, it must also explain the higher-the difference is one only of degree and of complexity; but then, also, if mechanism does not explain the higher, neither can it explain the lower. It has been said that thought is only translated motion, and that it is but the highest form of the universal mechanism. This theory is no doubt very alluring, inasmuch as it enables us to bring under one law all the phenomena of the universe, from simple impact up to the most complicated events of social life and history. But it is only an hypothesis, which is rendered doubtful by the fact that we can perceive no equivalence between thought and motion. Each appears to us as an ultimate fact, sui generis, and not reducible into the other.

To these theoretic considerations we may add others drawn from facts. If organization is the cause of instincts, then, as it varies, so must they. But observation shows that this is not the case. Observation teaches us that the correlation between instincts and organs is not absolute; that we may have the same organization with different instincts, and the same instincts with different organizations. Thus, the European beaver, which is hardly to be distinguished from the American, burrows like the mole, whereas the other builds houses. All spiders have the same apparatus for weaving their webs, and yet one spider weaves a circular web, another weaves a web of irregular form; a third weaves no web, but inhabits holes, simply making a door. Birds have their beaks and feet as their only instruments for nest building, yet how great are the differences of the form, architecture, and position of

nests.

Let it be granted for the moment that the opinion we are discussing is correct, although in the present state of our knowledge it is a mere hypothesis. Science has accustomed us to revelations so unexpected that it may be rash to say that the opinion is untenable. Assuming, then, that instinct is not the result of the organization, we shall still have to study its nature; for this hypothesis only enlightens us as to its cause. It tells us whence it comes, but not what it is. The reduction of all physical phenomena to motion does not bar the separate study of electricity, of sound,

heat, and light; nor would the reduction of all psychical phenomena to motion bar the separate study of instinct, sensation, imagination, will, etc. In any case, therefore, the question remains, What is

instinct?

Instinct is an unconscious form of intelligence, determined by the organization.

We intend to give in another place (Part III. chap. i. § 2) a detailed exposition of unconscious psychological phenomena, and to insist upon a class of facts that have been somewhat overlooked, though they probably contain much instruction for us. For the present, we would merely observe that, besides the conscious action of the mind, there is also an unconscious action, with a far wider sphere; that consciousness is an habitual, though not necessary, accompaniment of our mental life; that perhaps every one of these phenomena instinct, sensation, perception, memory, etc.—is by turns conscious and unconscious. This consideration will probably aid us to throw light on the problem of instinct.

Suppose a highly civilized people, among whom the division of labour is carried to great lengths; that it contains architects, poets, engineers, musicians, all incapable of any work save that which constitutes the specialty of each; that the architect can only build houses, and only a certain kind of house; the engineer only bridges, and such or such a kind of bridge; that the poet can only make verses - let us suppose, further, that each of them works unconsciously. These acts will certainly be regarded as instinctive, and we may compare the architect to the beaver, the engineer to the bee and the ant, the weaver to the spider, the carpenter to the termite. The only characteristic of instinct wanting would be innateness. This hypothesis exhibits the metamorphosis of intellectual acts into instincts: we had only to restrict intelligence within narrow limits and to deprive it of consciousness; we had to take away its suppleness and its manifold aptitudes, to impoverish, and, so to speak, to prune it.

But this is only an hypothesis which might properly enough be rejected. To look more closely at the question, we take a familiar fact, one known to all-somnambulism. The sleep

walker walks, runs, waits at table, like Gassendi's valet, writes verses, copies music, composes and revises sermons, solves pro

blems, even writes pages of philosophy, like Condillac. All this is done as well as and even better than in the waking state, and with as remarkable steadiness as in the case of instinct. The somnambulist, moreover, during the crisis, performs only acts which are habitual with him: the poet does not compose music, the musician does not write verses, nor did Condillac ever awake and find himself embroidering. Finally, it also resembles instinct, in that all its acts are performed unconsciously. If somnambulism were permanent and innate, it would be impossible to distinguish it from instinct. The resemblance was pointed out by Cuvier. 'We can gain a clear notion of instinct,' he well observes, 'only by admitting that animals have in their sensorium images, or constant sensations, which determine their action, as ordinary and accidental sensations determine action in general. It is a sort of dream or vision, which haunts them constantly, and, so far as concerns their instinct, animals may be regarded as a kind of somnambulists.' 'The organization of animals,' says Müller, 'is singularly favourable to the realization of the images, ideas, and inclinations which appear in the sensorium. As the internal and the external depend upon one and the same final cause, the form of the animal perfectly corresponds with its propensities. Thus, the instinctive propensities of the spider represent to it, like a sort of dream, the theme of its actions-the construction of its web.'

Here, again, in the case of somnambulism, all that is needed in order to bring about the metamorphosis of intellectual into instinctive acts is, that intelligence should be reduced to a few special acts (making verses, composing music, or the like), and that it should become unconscious. The phenomena of habit, which have been so justly compared with those of instinct, exhibit equally the transformation of intelligence into instinct. So soon as any intellectual operation, by repetition (that is to say, by restricting its domain), has become automatic (that is to say, unconscious), then the act is habitual or instinctive.

Hence it is less difficult than is generally supposed to conceive how intelligence may become instinct: we might even say that, leaving out of consideration the character of innateness, to which we will return, we have seen the metamorphosis take place. There can, then, be no ground for making instinct a faculty apart,

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