Hume, by Huxley

Chapter 5.

The Mental Phenomena of Animals.

In the course of the preceding chapters, attention has been more than once called to the fact, that the elements of consciousness and the operations of the mental faculties, under discussion, exist independently of and antecedent to, the existence of language.

If any weight is to be attached to arguments from analogy, there is overwhelming evidence in favour of the belief that children, before they can speak, and deaf mutes, possess the feelings to which those who have acquired the faculty of speech apply the name of sensations; that they have the feelings of relation; that trains of ideas pass through their minds; that generic ideas are formed from specific ones; and, that among these, ideas of memory and expectation occupy a most important place, inasmuch as, in their quality of potential beliefs, they furnish the grounds of action. This conclusion, in truth, is one of those which, though they cannot be demonstrated, are never doubted; and, since it is highly probable and cannot be disproved, we are quite safe in accepting it, as, at any rate, a good working hypothesis.

But, if we accept it, we must extend it to a much wider assemblage of living beings. Whatever cogency is attached to the arguments in favour of the occurrence of all the fundamental phenomena of mind in young children and deaf mutes, an equal force must be allowed to appertain to those which may be adduced to prove that the higher animals have minds. We must admit that Hume does not express himself too strongly when he says —

“no truth appears to me more evident, than that the beasts are endowed with thought and reason as well as men. The arguments are in this case so obvious, that they never escape the most stupid and ignorant.”—(I. p. 232.)

In fact, this is one of the few cases in which the conviction which forces itself upon the stupid and the ignorant, is fortified by the reasonings of the intelligent, and has its foundation deepened by every increase of knowledge. It is not merely that the observation of the actions of animals almost irresistibly suggests the attribution to them of mental states, such as those which accompany corresponding actions in men. The minute comparison which has been instituted by anatomists and physiologists between the organs which we know to constitute the apparatus of thought in man, and the corresponding organs in brutes, has demonstrated the existence of the closest similarity between the two, not only in structure, as far as the microscope will carry us, but in function, as far as functions are determinable by experiment. There is no question in the mind of any one acquainted with the facts that, so far as observation and experiment can take us, the structure and the functions of the nervous system are fundamentally the same in an ape, or in a dog, and in a man. And the suggestion that we must stop at the exact point at which direct proof fails us; and refuse to believe that the similarity which extends so far stretches yet further, is no better than a quibble. Robinson Crusoe did not feel bound to conclude, from the single human footprint which he saw in the sand, that the maker of the impression had only one leg.

Structure for structure, down to the minutest microscopical details, the eye, the ear, the olfactory organs, the nerves, the spinal cord, the brain of an ape, or of a dog, correspond with the same organs in the human subject. Cut a nerve, and the evidence of paralysis, or of insensibility, is the same in the two cases; apply pressure to the brain, or administer a narcotic, and the signs of intelligence disappear in the one as in the other. Whatever reason we have for believing that the changes which take place in the normal cerebral substance of man give rise to states of consciousness, the same reason exists for the belief that the modes of motion of the cerebral substance of an ape, or of a dog, produce like effects.

A dog acts as if he had all the different kinds of impressions of sensation of which each of us is cognisant. Moreover, he governs his movements exactly as if he had the feelings of distance, form, succession, likeness, and unlikeness, with which we are familiar, or as if the impressions of relation were generated in his mind as they are in our own. Sleeping dogs frequently appear to dream. If they do, it must be admitted that ideation goes on in them while they are asleep; and, in that case, there is no reason to doubt that they are conscious of trains of ideas in their waking state. Further, that dogs, if they possess ideas at all, have memories and expectations, and those potential beliefs of which these states are the foundation, can hardly be doubted by any one who is conversant with their ways. Finally, there would appear to be no valid argument against the supposition that dogs form generic ideas of sensible objects. One of the most curious peculiarities of the dog mind is its inherent snobbishness, shown by the regard paid to external respectability. The dog who barks furiously at a beggar will let a well-dressed man pass him without opposition. Has he not then a “generic idea” of rags and dirt associated with the idea of aversion, and that of sleek broadcloth associated with the idea of liking?

In short, it seems hard to assign any good reason for denying to the higher animals any mental state, or process, in which the employment of the vocal or visual symbols of which language is composed is not involved; and comparative psychology confirms the position in relation to the rest of the animal world assigned to man by comparative anatomy. As comparative anatomy is easily able to show that, physically, man is but the last term of a long series of forms, which lead, by slow gradations, from the highest mammal to the almost formless speck of living protoplasm, which lies on the shadowy boundary between animal and vegetable life; so, comparative psychology, though but a young science, and far short of her elder sister’s growth, points to the same conclusion.

In the absence of a distinct nervous system, we have no right to look for its product, consciousness; and, even in those forms of animal life in which the nervous apparatus has reached no higher degree of development, than that exhibited by the system of the spinal cord and the foundation of the brain in ourselves, the argument from analogy leaves the assumption of the existence of any form of consciousness unsupported. With the super-addition of a nervous apparatus corresponding with the cerebrum in ourselves, it is allowable to suppose the appearance of the simplest states of consciousness, or the sensations; and it is conceivable that these may at first exist, without any power of reproducing them, as memories; and, consequently, without ideation. Still higher, an apparatus of correlation may be superadded, until, as all these organs become more developed, the condition of the highest speechless animals is attained.

It is a remarkable example of Hume’s sagacity that he perceived the importance of a branch of science which, even now, can hardly be said to exist; and that, in a remarkable passage, he sketches in bold outlines the chief features of comparative psychology.

“ . . . any theory, by which we explain the operations of the understanding, or the origin and connexion of the passions in man, will acquire additional authority if we find that the same theory is requisite to explain the same phenomena in all other animals. We shall make trial of this with regard to the hypothesis by which we have, in the foregoing discourse, endeavoured to account for all experimental reasonings; and it is hoped that this new point of view will serve to confirm all our former observations.

First, it seems evident that animals, as well as men, learn many things from experience, and infer that the same events will always follow from the same causes. By this principle they become acquainted with the more obvious properties of external objects, and gradually, from their birth, treasure up a knowledge of the nature of fire, water, earth, stones, heights, depths, &c., and of the effects which result from their operation. The ignorance and inexperience of the young are here plainly distinguishable from the cunning and sagacity of the old, who have learned, by long observation, to avoid what hurt them, and pursue what gave ease or pleasure. A horse that has been accustomed to the field, becomes acquainted with the proper height which he can leap, and will never attempt what exceeds his force and ability. An old greyhound will trust the more fatiguing part of the chase to the younger, and will place himself so as to meet the hare in her doubles; nor are the conjectures which he forms on this occasion founded on anything but his observation and experience.

“This is still more evident from the effects of discipline and education on animals, who, by the proper application of rewards and punishments, may be taught any course of action, the most contrary to their natural instincts and propensities. Is it not experience which renders a dog apprehensive of pain when you menace him, or lift up the whip to beat him? Is it not even experience which makes him answer to his name, and infer from such an arbitrary sound that you mean him rather than any of his fellows, and intend to call him, when you pronounce it in a certain manner and with a certain tone and accent?

“In all these cases we may observe that the animal infers some fact beyond what immediately strikes his senses; and that this inference is altogether founded on past experience, while the creature expects from the present object the same consequences which it has always found in its observation to result from similar objects.

Secondly, it is impossible that this inference of the animal can be founded on any process of argument or reasoning, by which he concludes that like events must follow like objects, and that the course of nature will always be regular in its operations. For if there be in reality any arguments of this nature they surely lie too abstruse for the observation of such imperfect understandings; since it may well employ the utmost care and attention of a philosophic genius to discover and observe them. Animals therefore are not guided in these inferences by reasoning; neither are children; neither are the generality of mankind in their ordinary actions and conclusions; neither are philosophers themselves, who, in all the active parts of life, are in the main the same as the vulgar, and are governed by the same maxims. Nature must have provided some other principle, of more ready and more general use and application; nor can an operation of such immense consequence in life as that of inferring effects from causes, be trusted to the uncertain process of reasoning and argumentation. Were this doubtful with regard to men, it seems to admit of no question with regard to the brute creation; and the conclusion being once firmly established in the one, we have a strong presumption, from all the rules of analogy, that it ought to be universally admitted, without any exception or reserve. It is custom alone which engages animals, from every object that strikes their senses, to infer its usual attendant, and carries their imagination from the appearance of the one to conceive the other, in that particular manner which we denominate belief. No other explication can be given of this operation in all the higher as well as lower classes of sensitive beings which fall under our notice and observation.”—(IV. pp. 122–4.)

It will be observed that Hume appears to contrast the “inference of the animal” with the “process of argument or reasoning in man.” But it would be a complete misapprehension of his intention, if we were to suppose, that he thereby means to imply that there is any real difference between the two processes. The “inference of the animal” is a potential belief of expectation; the process of argument, or reasoning, in man is based upon potential beliefs of expectation, which are formed in the man exactly in the same way as in the animal. But, in men endowed with speech, the mental state which constitutes the potential belief is represented by a verbal proposition, and thus becomes what all the world recognises as a belief. The fallacy which Hume combats is, that the proposition, or verbal representative of a belief, has come to be regarded as a reality, instead of as the mere symbol which it really is; and that reasoning, or logic, which deals with nothing but propositions, is supposed to be necessary in order to validate the natural fact symbolised by those propositions. It is a fallacy similar to that of supposing that money is the foundation of wealth, whereas it is only the wholly unessential symbol of property.

In the passage which immediately follows that just quoted, Hume makes admissions which might be turned to serious account against some of his own doctrines.

“But though animals learn many parts of their knowledge from observation, there are also many parts of it which they derive from the original hand of Nature, which much exceed the share of capacity they possess on ordinary occasions, and in which they improve, little or nothing, by the longest practice and experience. These we denominate INSTINCTS, and are so apt to admire as something very extraordinary and inexplicable by all the disquisitions of human understanding. But our wonder will perhaps cease or diminish when we consider that the experimental reasoning itself, which we possess in common with beasts, and on which the whole conduct of life depends, is nothing but a species of instinct or mechanical power, that acts in us unknown to ourselves, and in its chief operations is not directed by any such relations or comparison of ideas as are the proper objects of our intellectual faculties.

“Though the instinct be different, yet still it is an instinct which teaches a man to avoid the fire, as much as that which teaches a bird, with such exactness, the art of incubation and the whole economy and order of its nursery.”—(IV. pp. 125, 126.)

The parallel here drawn between the “avoidance of a fire” by a man and the incubatory instinct of a bird is inexact. The man avoids fire when he has had experience of the pain produced by burning; but the bird incubates the first time it lays eggs, and therefore before it has had any experience of incubation. For the comparison to be admissible, it would be necessary that a man should avoid fire the first time he saw it, which is notoriously not the case.

The term “instinct” is very vague and ill-defined. It is commonly employed to denote any action, or even feeling, which is not dictated by conscious reasoning, whether it is, or is not, the result of previous experience. It is “instinct” which leads a chicken just hatched to pick up a grain of corn; parental love is said to be “instinctive”; the drowning man who catches at a straw does it “instinctively”; and the hand that accidentally touches something hot is drawn back by “instinct.” Thus “instinct” is made to cover everything from a simple reflex movement, in which the organ of consciousness need not be at all implicated, up to a complex combination of acts directed towards a definite end and accompanied by intense consciousness.

But this loose employment of the term “instinct” really accords with the nature of the thing; for it is wholly impossible to draw any line of demarcation between reflex actions and instincts. If a frog, on the flank of which a little drop of acid has been placed, rubs it off with the foot of the same side; and, if that foot be held, performs the same operation, at the cost of much effort, with the other foot, it certainly displays a curious instinct. But it is no less true that the whole operation is a reflex operation of the spinal cord, which can be performed quite as well when the brain is destroyed; and between which and simple reflex actions there is a complete series of gradations. In like manner, when an infant takes the breast, it is impossible to say whether the action should be rather termed instinctive or reflex.

What are usually called the instincts of animals are, however, acts of such a nature that, if they were performed by men, they would involve the generation of a series of ideas and of inferences from them; and it is a curious, and apparently an insoluble, problem whether they are, or are not, accompanied by cerebral changes of the same nature as those which give rise to ideas and inferences in ourselves. When a chicken picks up a grain, for example, are there, firstly, certain sensations, accompanied by the feeling of relation between the grain and its own body; secondly, a desire of the grain; thirdly, a volition to seize it? Or, are only the sensational terms of the series actually represented in consciousness?

The latter seems the more probable opinion, though it must be admitted that the other alternative is possible. But, in this case, the series of mental states which occurs is such as would be represented in language by a series of propositions, and would afford proof positive of the existence of innate ideas, in the Cartesian sense. Indeed, a metaphysical fowl, brooding over the mental operations of his fully-fledged consciousness, might appeal to the fact as proof that, in the very first action of his life, he assumed the existence of the Ego and the non-Ego, and of a relation between the two.

In all seriousness, if the existence of instincts be granted, the possibility of the existence of innate ideas, in the most extended sense ever imagined by Descartes, must also be admitted. In fact, Descartes, as we have soon, illustrates what he means by an innate idea, by the analogy of hereditary diseases or hereditary mental peculiarities, such as generosity. On the other hand, hereditary mental tendencies may justly be termed instincts; and still more appropriately might those special proclivities, which constitute what we call genius, come into the same category.

The child who is impelled to draw as soon as it can hold a pencil; the Mozart who breaks out into music as early; the boy Bidder who worked out the most complicated sums without learning arithmetic; the boy Pascal who evolved Euclid out of his own consciousness: all these may be said to have been impelled by instinct, as much as are the beaver and the bee. And the man of genius, is distinct in kind from the man of cleverness, by reason of the working within him of strong innate tendencies — which cultivation may improve, but which it can no more create, than horticulture can make thistles bear figs. The analogy between a musical instrument and the mind holds good here also. Art and industry may get much music, of a sort, out of a penny whistle; but, when all is done, it has no chance against an organ. The innate musical potentialities of the two are infinitely different.

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