Observations on Man (6th edition)/Part I/Chapter III/Section VII

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Section VII


Prop. XCIII.—To examine how far the Inferiority of Brutes to Mankind in intellectual Capacities is agreeable to the foregoing Theory.

If the doctrines of vibrations and association be found sufficient to solve the phænomena of sensation, motion, ideas, and affections, in men; it will be reasonable to suppose, that they will also be sufficient to solve the analogous phænomena in brutes. And, conversely, it seems probable, that an endeavour to apply and adapt these doctrines to brutes will cast some light and evidence upon them, as they take place in men. And thus the laws of vibrations and association may be as universal in respect of the nervous systems of animals of all kinds, as the law of circulation is with respect to the system of the heart and bloodvessels; and their powers of sensation and motion be the result of these three laws, viz. circulation, vibrations, and association, taken together. These three laws may also be most closely united in their ultimate cause and source, and flow in all their varieties from very simple principles. At least this is the tenor of nature in many similar cases.

As the whole brute creation differs much from, and is far inferior to man in intellectual capacities; so the several kinds of animals differ much from each other in the same respect. But I shall, in this Section, confine myself chiefly to the consideration of the first difference, viz. of that between mankind and the brute creation in general; and endeavour to assign such reasons for it, as flow from, or are agreeable to, the theory of these papers. We may suppose then, that brutes in general differ from, and are inferior to man, in intellectual capacities, on the following accounts:

First, The small proportional size of their brains.

Secondly, The imperfection of the matter of their brains, whereby it is less fitted for retaining a large number of miniatures, and combining them by association, than man’s.

Thirdly, Their want of words, and such like symbols.

Fourthly, The instinctive powers which they bring into the world with them, or which rise up from internal causes, as they advance towards adult age.

Fifthly, The difference between the external impressions made on the brute creation, and on mankind.

First, then, As the brains of brutes are less in proportion to the bulk of the other parts, than those of men; and as the internal parts of the brain appear from these papers to be the peculiar seat of ideas, and intellectual affections; it seems very natural to expect, that brutes should have a far less variety of these than men. The parts which intervene between the optic and auditory nerves, being proportionably less, for instance, in brutes, will not admit of so great a variety of associations between the several ideas of these senses, because the optic and auditory nerves cannot have so great a variety of connexions and communications with each other.

To this it is to be added, that the internal parts belonging to the olfactory nerves, and, perhaps, those belonging to the nerves of taste, take up, probably, a greater proportional part of the medullary substance of the brain than in us, since most brutes have the sense of smell, and perhaps that of taste in greater perfection than we have. There will therefore be still less room left for the variety of intercourses between the optic and auditory nerves in the medullary substance of the brain. And yet it is evident, from obvious observations, as well as from the whole tenor of these papers, that the eye and ear, with their associations, are the chief sources of intellect; and that the greatest part of the pleasures and pains of human life arise from visible and audible impressions, which in themselves afford neither pleasure nor pain.

Thus it is natural to expect, that the happiness and misery of brutes should depend principally, and in a direct manner, on the impressions made upon their gross senses, whilst that of mankind arises, in great measure, from long trains of associated ideas and emotions, which enter chiefly by the eye and ear. And it seems to me a very striking coincidence, that mankind should at the same time exceed the brute creation in the variety of their ideas, and in the proportional largeness of that part of the body which is the peculiar seat of these.

The same proportional largeness may, as it were, detain the vibrations which ascend from external impressions up to the brain, and so prevent that freedom of descent into the muscular system which takes place in brutes; and which disposes them to move more early, and more readily, in consequence of direct impressions, than men, at the same time that they have a far less command, in respect of voluntary motion. But this difference depends, in great measure, upon the considerations that follow, as will be seen.

Secondly, That the very constitution and texture of the nervous system, in its infinitesimal vessels, should differ in brutes from that of men, appears highly reasonable to be expected. And since the lives of brutes fall, in general, far short of that of man, also since the quadrupeds (which resemble man more than other animals) are far more hairy, and fowls have feathers, it appears probable, that the texture of the nervous system in brutes should tend more to callosity, and fixedness, in its dispositions to vibrate, than in men. The brains of young brute animals will therefore be sooner able to retain miniatures than those of children, as tending more to firmness and fixedness in their ultimate texture and constitution; at the same time that this texture will unfit them for receiving a variety. To which, if we add the shortness of their lives, and consequently of their ascent to the summit of adult age; which ascent is the proper time for receiving instruction; it is easy to see, that on this double account, as well as that mentioned under the foregoing head, they must fall far short of mankind in the number of their intellectual ideas, pleasures, and pains.

It follows from the same method of reasoning, that the few dispositions to miniature vibrations, which are generated in brutes, may be as perfect in their kinds; and consequently the memory, and short direct ratiocination depending thereon, as perfect also as the analogous things in man. Nay, they may be more so, if the particular animal under consideration excel man in the acuteness and precision of those senses, whose ideas make a principal part of this ratiocination. Now it appears, that most quadrupeds exceed us in the acuteness of the smell, and in the power of distinguishing a variety of smells. And many birds seem to be able to see distinctly at much greater distances. However, our auditory nerves, and the regions of the brain corresponding thereto, appear far better fitted for retaining a variety of miniatures of articulate sounds; and our optic nerves, and the regions of the brain corresponding thereto, for retaining a variety of miniatures of shapes and colours. And next to man, quadrupeds, and particularly monkies, dogs, and horses, seem to have these regions of the brain in the greatest perfection.

If the texture of the brains of animals here considered be also, in part, the cause of their being covered with hair, wool, bristles, feathers, &c. it may, from this its effect, dispose them to greater strength and expertness in their motions, and that more early, than happens to men. For all these are electrics per se, and consequently may first have a considerable degree of this power communicated to them by the heat of the circulating blood; and then, not being able to transmit it to the air, which is also an electric per se, may reflect it upon the muscles, and thereby dispose them to somewhat greater activity. It is well known, that the manes of horses, and backs of cats, are made electric by their vital powers. It may farther be observed, that the hoofs of animals are electrics per se, and that the feathers of water-fowl repel the water; whence the electric virtue may be kept from running off to the earth and water respectively. However, we ought not to lay much stress upon this electric virtue in the muscular fibres of brutes (if there be any such virtue) in order to account for the superior and more early powers of animals, in respect of ordinary motions. The texture of the fibres of the muscles, and that of the brain, must have the principal share in this effect.

It is also to be considered, that as they have far fewer voluntary motions, on account of having far fewer ideas, so they may arrive at a greater perfection in the automatic ones, and the small number of voluntary ones which they do perform, on this account. Man is distracted, as it were, by the endless variety of his ideas, and voluntary motions: and it is notorious, that none besides extraordinary geniuses arrive at perfection in any considerable variety; whereas a person of small natural capacity, by selecting some one branch of science, or manual art, and applying himself to this alone, may perform wonders. Nay, there have been instances of persons not much removed from idiotism, who could perform the arithmetical operations by memory, far better than men of good understandings, well versed in those operations; which is a thing somewhat analogous to the extraordinary sagacity in investigating and concluding, which brutes discover, in respect of some particular things.

Thirdly, The next circumstance which renders brutes far inferior to man in intellectual acquisitions, is their want of symbols, such as words, whereby to denote objects, sensations, ideas, and combinations of ideas. This may appear from several considerations. Those men who happen to be born in a country where the mother tongue is copious and precise, who apply themselves to the study of their mother tongue, who, besides this, learn one or more foreign tongues, &c. get, by these means, a considerable share of the knowledge of things themselves, learn to remark, prove, disprove, and invent, and, cæteris paribus, make a quicker progress in mental accomplishments than others. On the contrary, the mental improvement of persons born deaf is extremely retarded by their incapacity of having things suggested by articulate sounds, or the pictures of these, and also by their not being able to solve the inverse problem, and denote their own trains of thought by adequate symbols. Words are the same kind of helps in the investigation of qualities, as algebraical symbols and methods are in respect of quantity, as has been already remarked. Persons born deaf cannot therefore make any great progress in the knowledge of causes and effects, in abstracted and philosophical matters; but must approach, as it were, to the state of the brute creation. On the contrary, brute creatures, that have much intercourse with mankind, such as dogs and horses, by learning the use of words and symbols of other kinds, become more sagacious than they would otherwise be. And if particular pains be taken with them, their docility and sagacity, by means of symbols, sometimes arise to a very surprising degree.

Parrots might be thought, according to this view of the present subject, to have some particular advantages over quadrupeds, by their being able to pronounce words; since, as has been observed before, the attempts which children make to apply words to things, assist them very much in understanding the applications made by others. But parrots do not seem to speak from any particular acuteness and precision in the auditory nerves, and parts of the brain corresponding thereto, having no cochlea, but from the perfection and pliableness of their vocal organs, in which they exceed other birds; as birds in general do beasts. And it is reasonable to think, that quadrupeds, which resemble man so nearly in the make of the organ of hearing, as well as in other parts, and which also have naturally much more intercourse with man (being fellow-inhabitants of the earth) than birds (which inhabit the air), should likewise have a greater faculty of distinguishing the articulate sounds of man’s voice, retaining their miniatures, and applying them to the things signified, than birds; which seems evidently to be the case. Sagacious quadrupeds may therefore be said to resemble dumb persons arrived at adult age, who are possessed of much knowledge, which yet they cannot express, except by gestures, by dumb show: whereas parrots, as before remarked, resemble children; these having many words with very little knowledge annexed to them.

Apes and monkeys, of the several kinds, seem to approach nearest to man, in the general faculty of reasoning, and drawing conclusions; but in particular things, especially where instinct prevails, some other brutes far exceed them; as indeed such brutes do man himself in a few, on account of the peculiar acuteness of the sense of smell, and the same instinct.

I reckon the want of articulate sounds to be one of the reasons why brutes are so much inferior to men in intellectual capacities; because it appears, from the foregoing and other considerations of the same kind, that it is so. But this is no imperfection upon the whole. The proportional smallness of their brains, the texture of these, their instincts, and their external circumstances, are such, that they do not want language much; that they could make no great use of it, had they proper organs for speaking; and that they would probably be losers, upon the whole, by having it. The efficient and final causes are here suited to each other, as in all other cases; so that no circumstance can be changed for the better, cæteris manentibus.

Fourthly, Let us come to the instinctive powers of animals. These are a point of a very difficult consideration. They are evidently not the result of external impressions, by means of the miniatures of these, their associations and combinations, in the manner according to which I have endeavoured to shew that the rational faculties of mankind are formed and improved; and yet, in the instances to which they extend, they very much resemble the rational faculties of mankind. Animals, in preparing and providing for themselves and their young, in future exigencies, proceed in the same manner as a person of good understanding, who foresaw the event, would do; and this, even though they be a little put out of their way. And in this they much resemble persons of narrow capacities and acquisitions, who yet excel greatly in some particular art or science; of which there are many instances. Such persons shew great ingenuity in the things to which they are accustomed, and in some others that border upon them within certain limits, so as to shew great ingenuity still, though put a little out of their way; but if they be put much out of their way, or questioned about things that are entirely foreign to the art or science in which they excel, they are quite lost and confounded.

Let us suppose this to be the case, and then the inquiry concerning instinct in brutes will be reduced to this; viz. by what means the nervous systems of brutes are made to put on dispositions to miniature vibrations, analogous to those which take place in the persons here considered; and which are in them the result of foregoing impressions, if we admit the theory of these papers. Now, to me, there seems no difficulty in ascribing this to the mere bodily make in brutes, so that miniature vibrations, such as answer in us to ideas, and voluntary motions, shall spring up in them at certain ages and seasons of the year, and mix themselves with impressions, and acquired ideas, so as to be, in general, suitable to them; and, in general, to direct the brute creatures in what manner to provide for, and preserve, themselves and their young.

This would be a kind of inspiration to brutes, mixing itself with, and helping out, that part of their faculties which corresponds to reason in us, and which is extremely imperfect in them. Only this inspiration might be called natural, as proceeding from the same stated laws of matter and motion as the other phænomena of nature; whereas the inspiration of the sacred writers appears to be of a much higher source, so as to be termed supernatural properly, in contradistinction to all knowledge resulting from the common laws of nature. And yet it may result from some higher laws of nature. For sacred inspiration would lose nothing of its authority, though it should appear to be within such laws, as by their fixedness might be termed nature: and, indeed, all differences in these things, after the facts are once settled, will be found, upon due inquiry, to be merely verbal.

Fifthly, The last cause here assigned for the great difference and inferiority of brutes, in respect of intellectual capacities, is the difference in the events and incidents of their lives. They converse with far fewer objects than men, and both the objects and pleasures of feeling, taste, and smell, have a far greater proportional share in the sum total, than in us. Now, as in men, the common events and incidents of life give a turn to the whole frame of mind, and either enlarge the intellectual capacities, if they be various, or narrow them, if the same occurrences return again and again perpetually; so, independently of all the foregoing considerations, the sameness, paucity, and relation to mere sense, of the impressions made on brutes, must infer a great narrowness of understanding.

From all these things put together, it appears very conceivable how the mental faculties of brutes should, consistently with the doctrines of vibrations and association, be what they are, in fact, found to be. And though I suppose, with Descartes, that all their motions are conducted by mere mechanism, yet I do not suppose them to be destitute of perception, but that they have this in a manner analogous to that which takes place in us; and that it is subjected to the same mechanical laws as the motions. Whether the ideal vibrations, which take place in the medullary substances of their brains, be the result of former impressions, or the mere offspring of their vital and natural powers, agreeably to the foregoing hypothesis concerning instinct, or the compound effect of both, which we may presume to be generally the case, I always suppose, that corresponding feelings, and affections of mind, attend upon them, just as in us. And the brute creatures prove their near relation to us, not only by the general resemblance of the body, but by that of the mind also; inasmuch as many of them have most of the eminent passions in some imperfect degree, and as there is, perhaps, no passion belonging to human nature, which may not be found in some brute creature in a considerable degree.

The brutes seem scarce ever able to arrive at any proper self-interest of the abstract and refined kind, at consciousness, so as to compare and connect themselves with themselves in different situations, or at any idea and adoration of God; and this from the narrowness of their capacities and opportunities in general, but particularly from their want of symbols.

The same want of symbols must make all their reasonings and affections, which resemble ours in the general, be, however, considerably different in particulars, and far less complex; but it is sufficient to entitle them to the names of sagacity, cunning, fear, love, &c. by which ours are denoted, that the trains of ideal vibrations in their brains bear a general resemblance to the corresponding ones in ours, spring from like causes, and produce like effects.

The power of association over brutes is very evident in all the tricks which they are taught; and the whole nature of each brute, which has been brought up amongst others of the same species, is a compound of instinct, his own observation and experience, and imitation of those of his own species. Instinct seems to have exerted its whole influence when the creature is arrived at maturity, and has brought up young; so that nothing new can be expected from it afterwards. But their intellectual acquisitions from observation and imitation continue; whence old brutes are far more cunning, and can act far better, pro re nata, than young ones.

It ought always to be remembered in speaking on this subject, that brutes have more reason than they can shew, from their want of words, from our inattention, and from our ignorance of the import of those symbols, which they do use in giving intimations to one another, and to us.

We seem to be in the place of God to them, to be his vice-regents, and empowered to receive homage from them in his name. And we are obliged, by the same tenure, to be their guardians and benefactors.