['Animal Thought' © Stephen Walker 1983]
gif pdf file of this chapter

1   Descartes’s dichotomy

‘Animal thought’ could be an extremely short book. I could define thought as something which never occurs in animals, and spare myself and the reader any further efforts. There are certainly precedents for this—the weight of opinion is that animals don’t think, but people do. In this century, few psychologists have been disposed to argue the point: in fact, the main psychological movement which has concerned itself with animals, behaviourism, can be said to be founded on the proposition that neither animals, nor people, think.

The last ten or fifteen years have seen a turning away from the restrictions of behaviourism and a freer attitude to the study of mental life even within the bastions of academic respectability, It is appropriate therefore to exhume certain long-buried problems in the field of animal psychology, and to address new questions which have arisen from the application of modern behavioural and biological techniques.

That there are problems, both old and new, can be seen by examining a little more closely the assumption that thought is a uniquely human activity. There is such a long list of human attributes—speech and writing, art and science, savagery and civilisation—that it would seem at first sight sensible to conclude that every aspect of human mentality is unique. There is something to be said in favour of this conclusion, but difficulties appear when the characteristics of human knowledge are analysed into component parts. Thought can be defined as any form of mental activity, but the study of thought must always begin by the separating out of different kinds or modes of mental experience. Traditional categories include perception, memory, feeling, reasoning, awareness, reflection, foresight and intuition. Are all these things equally excluded to animals?


This is where subtle differences of opinion begin to blur the initial unanimity of view. Are all animals to be denied all of the various faculties of the human mind, or may we allow that certain of the most favoured members of the bestiary have feeling, but not reason, perception but not memory, or intuition with no reflection? There is at least room for argument. Before examining some of the arguments, it is worth pointing out that the questions are put in a form which asks about some, rather than all, members of the animal kingdom. The possibility of differences between animal species, aside from differences between animals generally and man particularly, will have to be taken seriously in later chapters. Strictly speaking, all forms of life not considered plants or fungi may count as animals, from single-celled organisms to primates. But clearly some species, such as the chimpanzee, are very much more like ourselves than others, such as tapeworms, and for that reason questions about human-like thought in chimpanzees are more important than similar questions about the tapeworm. I shall follow a technically improper, but common, usage, of usually meaning vertebrates, from fish to man, when I say animal, and in many cases the interest will mainly be in mammals. ,

I intend in this chapter to canvass the views of philosophers on the nature and extent of thought in animals. The limits of human knowledge, and in particular its relationship to perception via the senses, and to intuition, reason and language, are topics that philosophers have opinions about. The ways in which human thought and knowledge depend on the human brain—the mind-body problem—is, like the other matters, the subject of highly technical philosophical considerations, However, I shall attempt to use the mind-body problem as an avenue by which the area of animal thought can be approached. Briefly, there is a considerable body of work which attempts to show that the human mind can be conceived of entirely in terms of states of the human brain. Since there is a large amount of scientific evidence available concerning the similarity of human and animal brain function, tying human thought to brain function automatically implies a continuity between human and animal thought.

Any survey of views on the status of the animal mind should, however, begin with Descartes (1595—1650), who denied its existence. Descartes is considered to be the father of modern philosophy, since he believed that the application of a scientific method could supply new


and better answers to all questions about the physical nature of the universe. He is in many ways a paradoxical figure, a reductionist who wished to discuss geometry in terms of numbers, and physiology in terms of geometry, but yet a supporter of theological orthodoxy. Whether his religious orthodoxy was a product of Conviction or convenience is uncertain, but it was strong enough to make him suppress the publication of his major work Le Monde when he heard of Galileo’s run in with the Vatican in 1633. Only fragments of Le Monde were ever published (after his death) and possibly in this or other unpublished work Descartes experimented with out-and-out materialism, doing away with souls in either animals or men. It is certain that he shared Galileo’s heretical views about the rotation of the earth, and the infinity of the universe, and there are points where his analysis of human physiology begins to make the soul seem superfluous. But his positive and published statements about the separation of the soul from the body are clear enough. In a craven and slavish dedication of his Meditations to ‘the very sage and illustrious Dean and Doctors of the Sacred Faculty of Theology in Paris’, Descartes avows the goal of his work to be to convince infidels and atheists of the reality of God. In the Discourse on Method, for which he is largely remembered as a philosopher, he says that, as theological errors go, ‘there is none more powerful in leading feeble minds astray from the straight path of virtue than the supposition that the soul of brutes is of the same nature with our own.’ (Feeble- minded readers, beware!)

The dangers of the assumption that animals have souls like our own are not now particularly obvious. At the time the worry was apparently that the hopes and fears about life after death, which were held responsible for keeping feeble minds to the straight and narrow during their earthly sojourn, would somehow be diminished by the proposition that flies and ants would also be present on the Day of Judgment. But as aids to conscience other religions have made use of a supposed interchangeability of souls by threatening miscreants with a future life as a fly or an ant. An alternative tactic would be to allow animals inferior and temporary souls, which did not survive after death, or to allow animals immortal souls, but diminished moral responsibilities. St Thomas Aquinas, for instance, was considerably more charitable towards animals in terms of their mental capacities and possible after-life than Descartes (see Aquinas’s Philosophical Texts, 1951).

Because Aquinas accepted both an Aristotelian scale of being, and


the Platonic version of souls which can be present even in vegetables and inanimate objects, his estimation of animal intelligence matches or exceeds that of the most anthropomorphic post-Darwinians. In Aquinas’s view there is a fairly continuous grading of souls between plants and God, with animals distinguished from plants by having sensitive souls—animals perceive external objects through their senses, and this data is held in the imagination before entering the deeper store of memory. The sensitive powers of animals are ‘conscious within themselves’ and consequently ‘what begins from without is worked up from within’—a very sophisticated kind of information processing. Men are superior to animals in having intellective souls which can reason, deliberate, and reflect on themselves. However, animals, especially the higher ones, retain and preserve their perceptions, exhibit anticipatory actions, can adapt means to ends, and can perceive purposes not immediately apparent to the external senses. As far as the purely sensitive or perceiving soul goes:

Man’s superiority to beasts in animal shrewdness and memory does not result from anything proper to the sensitive part, but from an affinity and closeness to intelligence which, so to speak, flows into them. These powers in man are not so very different from those in animals, only they are heightened. (Aquinas, 1951, p. 230)


Because the role assigned to the animal soul in sensing and feeling is very much the same as that for the human soul performing similar functions, Aquinas is able to speak of the souls of horses and the souls of men in the same breath, and to entertain the idea that the souls of animals are immortal. He thinks that this would be improbable, but notes that it would not conflict with Plato (see 1951, p. 199 and also pp. 182, 195, 198, 201, 203, 228—30, and 256).

Although Aquinas wrote in the thirteenth century, he was the major theological authority of the fifteenth, and one to whom Descartes might have appealed—Aquinas having been a member of the Faculty of Theology which Descartes tried to placate. Descartes was not being particularly conventional in denying the existence of an animal soul; on the contrary, the mechanistic interpretation of animal behaviour could be seen as a suspicious change in the tradition of having souls with everything—and this may explain Descartes’s protestations of virtue and orthodoxy in the case of man. Descartes was not original in


being a dualist, but innovative in abandoning dualism for animals other than man.

Descartes’s dualism

When Descartes moved from Paris to Holland, where he was to live for twenty years, he took with him very few books, but among them were the works of Aquinas. His own theories stripped away most of Aquinas’s dualism, substituting systematic materialism and determinism. All life with the exception of the human soul became, in Descartes’s hands, reducible to the laws of physics. In his view, animals are unthinking machines, or automata, lacking conscious perception of even the immediate world about them. There is thus a fixed and unbridgeable dichotomy, with animals, as machines, on the one side, and men, possessing rational souls, on the other.

There are three parts to Descartes’s argument that animals are automata. The first is the argument by analogy with the clockwork models popular at the time. The most long-lived example of these toys is the cage of mechanical canaries. If such things can be fabricated by human industry, says Descartes in the Discourse on Method, how much better might be machines put together by the hand of God? The second theme, by which more substance is added to this analogy, is the detailed description of mammalian sensory physiology and anatomy—the divine biological machinery. Descartes was most concerned with the sense of vision (dioptrics), but he was also a fervent admirer of Harvey’s experiments which demonstrated the circulatory function of the heart, and gives a comprehensive account of emotion and perception of the sort one would nowadays find in a textbook of physiological psychology (see Principles of Philosophy (1978a), part IV, and Passions of the Soul (1952)). Although his physiology was rather primitive by modern standards, if one interprets ‘movements’ passing through nerves as their electrical activity, and ‘animal spirits’ as brain chemicals, some of what Descartes said would not be out of place in an up-to-date text. His own experiments included the dissection of an ox’s eye with observation of the inverted visual image formed on the retina. His discussion of why the inversion of the image does not matter, because features of the information contained in the image, not pictures themselves, are transmitted down the optic nerve, is fascinating, and the account of the roles of binocular disparity and eye


movements in the perception of distance, and the automatic adjustments of pupil size and focal length in the eyeball, are hard to fault. There may have been much that Descartes did not know about the neurophysiology of the visual system, but his description of how the perceived qualities of brightness and colour (the only qualities peculiar to sight) and position, distance, size and shape are ‘determined by the strength of disturbance’ at the eventual termination of the ‘optic nerve fibres in the brain’ is remarkably consistent with recent theories, as is also his discussion of the after-images and visual persistence experienced when we close our eyes after looking at bright objects.

Ironically, the strength of Descartes’s theories was largely due to his general idea that perception and feeling should be interpreted in terms of a one-to-one correspondence with neural states of the brain. In his view, of course, there was a further one-to-one correspondence between states of the brain and experiences of the soul, but the rigour with which he developed the first correspondence was original and exceptional (especially bearing in mind the naivety of some of his contemporaries, such as the English philosopher Hobbes, who still believed emotions were experienced in the heart). Descartes analysed taste, smell and hearing, as well as vision, in terms of the motions existing in the relevant sensory nerves, but the general flavour of his theory is given here:

We must know, therefore, that although the human soul is united to the whole body, it has, nevertheless, its principle seat in the brain, where alone it not only understands and imagines, but also perceives; and this by the medium of the nerves, which are extended like threads from the brain to all the other members, with which they are so connected that we can hardly touch one of them without moving the extremities of some of the nerves spread over it; and this motion passes to the other extremities of those nerves which are collected in the brain. . . . the movements which are thus exited in the brain by the nerves, variously affect the soul or mind, which is intimately conjoined with the brain. (Principles, 1978a, part IV, §II, pp. 214—15)


The arguments with which Descartes supported his thesis that perception and feeling take place in the brain, and are to some extent isolated from other parts of the body, and from external objects, are instructive, and some of them have been repeated ever since. The most


familiar to readers of present-day psychological texts is probably the argument from the ‘phantom-limb’ phenomenon. In the Principles, Descartes quotes the case of a girl with an ulcerated hand, who had her eyes covered whenever the surgeon changed the dressings as she could not bear the sight of the sores. Amputation at the elbow became necessary, and in Descartes’s story linen cloths were substituted to give the impression of a remaining forearm. After the operation the girl continued to Complain of pain in the now absent hand—sometimes in one finger and sometimes in another. Descartes gives the now standard explanation that neural messages reaching the brain mimicked those which occurred with the limb intact. Retained subjective feeling ‘in’ the removed limb is a common phenomenon after amputations, even without subterfuges to disguise the limb’s absence, and the fact is still used to support physiological theories of sensation (e.g. Hebb, 1966). Similarly, ‘seeing stars’ after a blow on the head, or after relatively minor distortions of the eyeball, suggested to Descartes that it is activity in the optic nerve which gives rise to the subjective sensation of light. But the sensory nerves for the various modalities look sufficiently similar to one another to imply that they all convey information to the brain in the same form. Therefore we should assume that nothing at all reaches the brain besides ‘the local motion of the nerves themselves’ (Principles, 1978a, part IV, §XI)..

The observations on nerves, and on the structure of the eye, applied to animals; but by working out in such detail the way in which sensory and nervous apparatus functioned, Descartes was painting himself into a corner, with his soul uneasily surrounded by mechanisms. Others, such as La Mettrie (1709—51), completed the job, and became pure mechanists or materialists, supposing that the conscious perceptions of both animals and men can be explained by a sufficiently detailed account of brain functioning. What were Descartes’s grounds for resisting this extension of his own physical determinism? Apart from extraneous theological motives, there was an aspect of Descartes’s systematic method which approached the problem of sensation from another direction—the method of doubt concerning all subjective knowledge.


Descartes is remembered not so much for his neurophysiology as for his proposition that while one can doubt the existence of sensory mechanisms, or the existence of the body itself, one cannot doubt the subjective experience of perception, or if one does, one cannot then


doubt the subjective experience of doubting. Because of this, ‘I think therefore I am’ is given a higher value than studies of mechanism, and the soul is assigned the role of doing the thinking, doubting and feeling. It is important to emphasise that Descartes takes thinking in this context to be anything we are subjectively conscious of, including sense- impressions and emotions—he does not draw the distinction between reasoning and perceiving that others do, and this eventually determines the reduced status of animals in his system (see Descartes, 1970, translator’s note, and ‘By the word thought, I understand all that which so takes place in us that we of ourselves are immediately conscious of it’; Principles, 1978a, part I, §IX). In other words, ‘cogito, ergo sum’ is in the first place an existential appeal to the primacy of all subjective consciousness.

Since Descartes makes it abundantly clear that, in man, subjective consciousness is very intimately connected with brain mechanisms, why is it not so that animals, in so far as they have similar brain mechanisms, have similar subjective consciousness? This remains a problem. Undoubtedly a motive for denying animals any subjective consciousness arose because, in stressing the unity of conscious experience, Descartes had conflated Aquinas’s sensitive and intellective souls, and was thus faced with giving animals all or nothing. The main argument for giving them nothing, rather than all, repeats the grounds for denying animals intellective faculties, which, since these have become closely bound up with perceptual and emotional awareness, means than when animals fail the intellectual tests, they lose the limited but appreciable spiritual status that Aquinas had been prepared to allow them.

These tests supply the third part of Descartes’s proof that animals are automata: they are means by which men with souls can be distinguished from animals or cunningly constructed mechanical devices. The difference between a man and an ape is that a machine constructed to look and act exactly like an ape would be indistinguishable from the real thing but, if a similar machine were made to mimic a man ‘as far as is morally possible’, then we should be able to apply two tests to this robot, which it would fail (Discourse, 1978a, pp. 44—7).

The first test is creative language. It is supposed that the robot might be able to cry out that it is hurt, or ask what the next question is, ‘and such like’, when appropriate buttons are pushed. But it could never, according to Descartes, be made to speak well enough ‘so as appositely to reply to what is said in its presence, as men of the lowest grade of


intellect can do’. This was an argument developed by Turing, the English mathematician whose ideas did much to foster interest in computers, but Turing was not so sure that a robot, or a computer, would necessarily fail the test. Already there are computers which can recognise simple spoken instructions, and there are computer programs which can play the part of a psychotherapist in interchanges with real patients (Holden, 1977), so the inability of machines to conduct low-grade conversations is no longer such a strong point.

By the conversation test ‘we may likewise know the difference’ between men and brutes. Since animals refuse to converse with us at all, even though parrots and magpies are quite capable of producing the requisite sounds, and even though human idiots, and the deaf and dumb, can make their thoughts understood: ‘this proves not only that the brutes have less reason than man, but that they have none at all’ (Discourse, 1978a, p. 45). This argument has had a considerable influence on research in linguistics and comparative psychology over the last twenty years. Chomsky tends to appeal to Descartes as an authority to support the view that something very profound is lacking in animals, while much effort has been spent on trying to show that Descartes was empirically wrong, by persuading chimpanzees to ‘make their thoughts understood’. The whole question of the communication of ideas by animals will need to be addressed in a later chapter. But we may note here that, accepting for the time being the empirical correctness of Descartes’s supposition that animals will not converse with us, it is still a rather unjustly stringent test on which to base the conclusion that animals have no reason at all, unless we define reason in terms of human language: some capacity for inference and problem-solving might be allowed for in the complete absence of Communicative expression.

More strongly, it is obvious that as it stands, the conversation test is unsuitable for eliminating perception and feeling in animals, except in forms that are intimately concerned with language. Descartes is extremely unusual, though not alone, in lumping together understanding, willing, imagining, perceiving and feeling, as all equally restricted to the human mind. He goes so far as to say that ‘I walk, therefore I am’, or ‘I see, therefore I am’, are equivalent to ‘I think, therefore I am’ (Principles, 1978a §§I, IX). ‘Consciousness of seeing or walking’ is ‘referred to the mind, which alone perceives or is conscious that it sees or walks’. As walking or seeing are made just as special as thinking in their relationship to the mind, this means that if it appears


that animals do not think as we do, one has to conclude that their seeing and walking are just as different from our own, despite other evidence to the contrary. According to Descartes, the difference is of course that animals are purely and only automata, lacking not only reason and choice but any form of conscious sensitivity; man shares with animals the biological machinery necessary for perceiving and acting, but conscious perception and action, as well as speech and rational choice, only become possible because the machinery interacts with, and is directed by, the human soul.

What of Descartes’s second test? This is somewhat more obscure, and seems rather more applicable to the question of the limits of manmade machines than to the investigation of the capabilities of animals. It is that ‘although such machines might execute many things with equal or perhaps greater perfection than any of us, they would, without doubt, fail in certain others from which it could be discovered that they did not act from knowledge’: they could act only for specific purposes, in accordance with the prior organisation of the constituent bits of their working parts; we on the other hand can use reason in a creative fashion, to apply to every possible set of circumstances. Our reason is flexible, inventive and universal, whereas machines can only accomplish tasks they have been built to perform. This seems to be a clear foreshadowing of Lady Lovelace’s objection to her friend Charles Babbage’s nineteenth century brass calculating machines. No matter how elaborate the brass gears and differentials, such apparatus can only ever do what it is designed to do in the first place. This certainly applies to the typical way in which we tend to use electronic computers—they can be very fast at calculating bank balances, but are not programmed to show the same degree of judgment and initiative in response to overdrafts as we would hope for from our bank manager. Whether it is theoretically impossible ever to build electronic devices which are capable of matching human judgment and initiative is another matter—there are many who think so, for reasons similar to Descartes’s, but others, working in the field known as ‘artificial intelligence’, believe that, given sufficient time and money, it could be done. Pocket-sized computers are now available that can play chess at a typical, if not outstanding, human level, accompanied by a rudimentary attempt at conversation about the game, but these are grist to the mill of Descartes’s second test, since they have particular internal arrangements to control particular actions. In the face of modern electronic technology, though, it is less obvious that it is


impossible for physical devices to achieve human flexibility than it was in the seventeenth century.

However, the question of consciousness and thought in machines is still rather different from the same question applied to animals, at least in this, that we know how the machinery works in physical devices, and we know that it is different from our own machinery, while although we know less about the biological machinery contained in human and animal nervous systems, its method of operation, in terms of neural transmission, brain chemistry and soon, is sufficiently similar in man and animals to make it difficult to draw a clear line between man and animals on the grounds of internal physical design.

But Descartes did draw the line, and might claim today that animals can be considered as having the same moral and intellectual status, more or less, as a collection of microchips, while the human species is distinguished by the privileged intercommunication of its internal computing processes with conscious and rational souls. If there are those to whom such a dichotomy would now seem ridiculous, it may be pointed out that Sherrington, a pioneer in the modern study of neural mechanisms, put forward a view like this in the 1930s, and Eccles, an equally eminent neurophysiologist, has maintained a pure Cartesian dualism of this kind, most recently in a version developed with the collaboration of the philosopher Karl Popper (Eccles, 1965; Popper and Eccles, 1977; Sherrington, 1940). On the other hand, those to whom Descartes’s theory seems in accord with their own intuitions and convictions ‘should be aware of the numerous logical difficulties, inconsistencies and incongruities which have plagued Cartesian dualism since its inception. I am most concerned here with the dichotomy between man and animals, but problems on either side of the line—is it correct to consign animals to the oblivion of the mechanical? is it possible to interpret man as a conjunction of the mechanical and the ethereal? —both have a bearing on the plausibility of the dichotomy, even though most attention is naturally given to the human condition.

The main objection expressly put to Descartes concerning his treatment of the animal world was in fact emotional, rather than logical. Henry More, a Cambridge don, wrote to Descartes:

But there is nothing in your opinions that so much disgusts me, so far as I have any kindness or gentleness, as the internecine and murderous view which you bring forward in the Method,


which snatches away life and sensibility from all the animals. (Williams, 1978, p. 282) .

Bernard Williams (1978) comments that this seems to give vent to a particularly English spirit of outrage—whatever it is about English culture that produces a concern for animal welfare, it was clearly evident in the seventeenth century. (And no doubt before: in Thomas More’s Utopia written a century earlier, only bondmen were allowed to kill the animals kept for food.)

Technical difficulties of logic were put to Descartes by the English philosopher Hobbes, who as a Royalist extremist and suspected atheist fled to Paris in 1640 at the beginning of the Long Parliament, just when Descartes was preparing the Meditations. Hobbes saw these before they were published, and Descartes printed his objections to them, along with his own replies. Hobbes’s comments were biting, if good-humoured. Descartes rested a good deal of his subjectivism on the difficulty of knowing whether one is awake or dreaming—if waking life is just another dream, this is a ground for doubting everything but our own awareness. Says Hobbes: ‘it is a common observation how hard it is to tell waking life from dreams. So I am sorry that so excellent an author of new speculations should publish this old stuff. Replies Descartes: ‘such doubts seem to me to be quite indispensable, and I did not use them to hawk them about as novelties’ (Descartes, 1970, p. 127). This is an introductory knockabout; Hobbes’s Second Objection points out what has become a hardy perennial (Ryle, 1949; Williams, 1978)—there ought to be a distinction between an experience itself and the existence of the experiencer. Hobbes does not agree that ‘I think, therefore I am’ implies the existence of a soul:


It seems not to be a valid argument to say ‘I am conscious, therefore I am consciousness’, or ‘I am intelligent, therefore I am an intellect’. For I might as well say ‘I am walking, therefore I am a walk’. (Descartes, 1970, p. 128)


This is the first, though not the last, indication that resting a philosophical system on immediate subjective awareness may not be as conclusive as it appeared to Descartes. Hobbes puts forward as an alternative to the necessity for a reasoning soul a materialist account of


verbal inference. He proposes that we learn the names of things, and then learn to combine the names according to certain conventions:


If so, reasoning will depend on names, names on imagination, and imagination perhaps (and this is my opinion) on the motions of the bodily organs; and thus the mind is nothing but motions in certain parts of an organic body. (Descartes, 1970, p. 133)


This is a useful example of a ‘nothing but’ concept of mind which does without anything immaterial. The superiority of the human over the animal mind would for Hobbes depend not on non- corporeal essences, but on the development of names, conventions for using them and also on covenants allowing for social institutions. Without these artificial conventions and covenants, human life would be literally brutish, as well as nasty and short (Watkins, 1973).

It is ironic that Descartes, the dualist, had such a clear idea of the importance of the brain, whereas Hobbes spoke of motions in the bodily organs generally. However, Descartes’s attempt to pin down the crucial organ of consciousness is hardly any better than leaving reason to the heart or liver. He did not, in the first instance, describe in any detail the interaction of the soul with the body, beyond saying that one’s soul is united to the body as a whole, but has its principal seat in the brain (Principles, 1978a). He was led to make various elaborations primarily by the intervention of the young Princess Elizabeth of Palatine. Although she was not the only reader to be dissatisfied by the Principles, Descartes had dedicated the book to her, and in the dedication rather touchingly congratulated her on her intellectual powers, which were evident to him, he says, partly because she had understood his previous work better than anybody else. She had been his pupil, and their relationship was apparently one of affection as well as mutual scientific interest. There seems little doubt that Descartes took her criticisms seriously—Passions of the Soul, which was to be his final work, was written partly in response to them. Although Elizabeth wished her letters to Descartes to be destroyed, and it was not until 200 years later that some of them turned up, those which survive suggest that she was a worthy adversary. She was the aunt of George I, but also a Stuart, her cousin, Charles II, being founder of the Royal Society. (It may be the case that royal females held a special fascination for


Descartes, or vice versa. At the height of his success, he took up an appointment as tutor to Queen Christiana of Sweden. For someone who had done his best thinking while sitting in a large oven, this was unwise, and a chill attributed to early morning discussions with the Queen in the middle of winter proved fatal.)

Elizabeth of Palatine’s criticisms were succinctly put, go directly to the heart of Descartes’s system, and may be applied to any subsequent version of dualism. If an immaterial and purely mental structure is assumed (a) to receive information from the physical body, and (b) in turn, to react back and control the sequence of physical events in the body, the interface between the mental and the material presents a number of problems. First, how can real matter (whether atoms and molecules, or animal spirits) be pushed and pulled about by something which is by definition not part of the physical world? Second, how does the immaterial mind gain information from the physical world, while remaining separate from it? Third, if one can allow that the mind may extract useful messages from the body, why is it also necessary for mental states to be enslaved by all sorts of bodily conditions?

Elizabeth, and generally other critics as well, were ready to accept that an immaterial mind could observe the material world, and choose to be influenced by it. But she felt that there were contradictions in the idea that the soul, with no extension in space, and no physical properties or dimensions, could instruct the body in voluntary actions. Descartes’s first attempt at an answer was to say that the soul moves the body in the same way that gravity moves lifeless objects. Today he might still refer to gravity, or to electromagnetic fields: theoretical physicists are notoriously seducible by the psychic and the paranormal. Elizabeth, however, pointed out that gravity was surely part of the physical world, that Descartes had said in discussions of physics that it was an aspect of matter, and that gravity could hardly have the same relation to God as a soul, and that the idea of gravity as something that carried objects to the centre of the earth might in any case be theoretically unsound. Descartes had to write back that gravity was rather a lame simile, and that perhaps the best idea was to think that the soul did have matter and extension, since this is more or less what he had meant by his repeated assertion that a soul is united to its body, in order to be able to act and suffer along with it (Descartes, 1970, pp. 274—82).

The principle of intimate conjunction between soul and body must also be applied to the third problem, the unseemly dependence of the


soul on bodily conditions. If the soul possesses all ‘the power and the habit of correct reasoning’, why are these powers so disturbed by an attack of the vapours, asked Princess Elizabeth. Why is the soul ‘so much governed by the body, when it can subsist separately, and has nothing in common with it’? Descartes’s answer is that the soul must pay a high price for being so entangled with the body as it is. Although it is present and conscious in the foetus, it cannot do much reasoning there because of the novelty of its new sensations, and in adulthood, the intermingling of mind and matter means that brain fatigue, sickness or bodily distractions may interfere with mental functions, and consciousness is of course suspended while the brain sleeps.

This is still rather vague, and Descartes prided himself on not leaving anything out of his system. In Passions of the Soul we are given a more detailed, though also, it must be said, a more confused and contradictory, account of the relations between body and mind. Again it is central that though the body does many things, it does not think (Passions, 1952, Article 4). It is still stated that ‘the soul is united to all parts of the body conjointly’ (Article 30), until it withdraws itself from the body in its entirety, as a consequence of the body’s cooling after death (Article 5). However, most of the mind’s business is conducted through a small part of the brain—the pineal gland. This was an unfortunate choice in terms of later anatomical plausibility, since it is hard to think of a structure in the central nervous system which is now thought to have less connection with human reason than this gland. In terms of size, it seems to have had most importance in certain extinct reptiles, and in general the pineal gland is thought to have the function of modulating hormonal secretions in accordance with light cycles. In man it is exceedingly small but, according to Descartes, especially mobile. His main reason for choosing it was the fact that it is positioned in the centre of the brain, and is not duplicated (Article 32).

The way in which Descartes thought that the pineal gland worked went like this. First, it was the point at which the soul received sensations. For instance, visual images from the two eyes travel down the optic nerves, and eventually fuse at the same place on the pineal, and this causes the soul to see a single image (the strictures against little pictures in the brain seem to have been suspended). Next, the pineal gland initiates voluntary action. While Descartes supposed that sensory nerves transmitted information to the brain as if they were strings being pulled, he thought that motor nerves worked by a sort of pneumatic pushing, with liquids or gases (the ‘animal spirits’)


travelling down, through the motor nerves, from the ventricles of the brain to muscles; the idea being that when we wish to make a particular movement, the wish in the mind causes the pineal gland to pump animal spirits to the appropriate muscles (Article 7). When we wish to remember something the gland is caused to bend, ‘now to one side and now to another’, impelling animal spirits towards this and that region of the brain, until they come upon pores of the brain that have been expanded by use in a way that matches the particular movements of the animal spirits. When this has happened, a special movement is exited, back at the gland, which enables the soul to ‘know what it wished to remember’ (Article 42). This takes care of memory, but with memories stored in the body. Attention is explained somewhat more simply since ‘when we wish to hold our attention fixed for some little time on some object, this volition keeps the gland bent in this direction’ (Article 43). Conflict between body and mind takes place when the soul tries to move the gland to one side, but the animal spirits push it in the opposite direction (Article 47). Language learning occurs as the soul learns habits which allow the meanings of words to be put into a code of pineal gland movements that produce appropriate activities in the tongue and lips (Article 44).

With the hindsight of more recent knowledge of brain function, this may appear to be an extremely strange and fantastic theory. However, we should try to ignore the physiological details. Would the theory be improved by saying that, instead of the pineal gland, a network of cells in the cerebral cortex of the human brain, which all now agree is very much concerned with cognition and language, serves as the interface between an immaterial conscious mind, and the physical activity of the brain? For movements of the pineal gland, we could substitute the activation of certain patterns of cells in the cortex. This is more or less the modification of Descartes’s theory proposed by Eccles (1965 and see Popper and Eccles, 1977), who provides the convenient metaphor of the brain containing a radio transmitter-receiver unit, which acts as the liaison between mind and body. We would thus view animals as robots acting mechanically, controlled by mechanisms confined to the brain, with ourselves having the same internal connections plus two-way communication with an immensely more powerful conscious and immortal control centre.

Would this account have satisfied the critical judgment of Princess Elizabeth of Palatine? The analogy of radio waves might well have proved more convincing that the analogy of gravity, though one


suspects that the Princess, as a Calvinist, would not have been entirely happy with the idea of the soul as a sort of personal telephone call-in programme. However, even if we granted that some as yet undetected limited liaison may be available to interrelate brain function with personal consciousness, some of the problems remain. If consciousness is independent of the brain, but in communication with it, why is consciousness disturbed by brain malfunctioning? Because subjective states are at the mercy of the vapours, or, if you like, Valium, it is much clearer that consciousness is determined by physical states of the brain than it is that a separate mind perceives and acts through the brain. If there is a reasoning process which is independent of the body, how is it that reasoning can be substantially altered by a few glasses of wine? It is precisely because of these peculiarities that Descartes rejected the notion of a soul which was only in liaison with the body (the rejected Platonic metaphor being that of a pilot steering a ship) in favour of a mind which is united and conjoined with the body. If the mind only interacts with the brain as a pilot steers his ship, or as a driver controls his car, the everyday interdependence of mind and body is left out. Malfunctions of the car might prevent the driver steering, but they should not incapacitate the driver himself, whereas malfunctions of the brain can directly affect every subjective experience, and alter every mental capacity.

Materialist theories of mind

Descartes’s dualism of mind and body, which gives rise to the dichotomy between man and animals, is far from being satisfactory, and other versions of dualism, such as those of McDougall (1911), Broad (1937), Sherrington (1940) and Eccles (1965) suffer from many of the same difficulties, even though they lack the absurdities of the pineal gland theory. Armstrong (1968) reviews yet more varieties of dualism, including those where the problems of mind/body interaction are sidestepped by saying that there is no interaction. This tactic is referred to as epiphenomenalism or parallelism, and, though the problems of interaction are disguised, the explanatory force of dualism is thereby diminished. Other watered-down versions of dualism are the ‘double aspect’ or ‘attribute’ theories, where brain and mind are said to be alternative facets of the same thing. However, few subsequent theorists have made as plain a stand as Descartes on the issue of animal


minds, which is our main concern here. Even Eccles is argued into ‘agnosticism’ on the question of animal consciousness by Popper, who believes that animals have subjective experiences without a fully developed consciousness of self, or other human attributes (Popper and Eccles, 1g77, p. 518).

We should now examine the materialist alternatives to dualist theories of mind. We have seen that Hobbes was content to define mind as ‘nothing but’ forms of bodily activity. A number of more sophisticated modern versions of this materialist strategy are available, under the names of identity theory, physicalism, materialism, or central state theory (e.g. Armstrong, 1968; Levin, 1979; Quinton, 1973; Russell, 1959; Wilkes, 1978). The essential theme is that mind, in all its glory, is physical, material, identical with states of the brain, and nothing else. Epigrammatically, ‘the mind is simply the brain’ (Armstrong, 1968, p. 73). I shall, for convenience, refer to these accounts generically as brain-state theories. There are many subtle differences between them in argument and conclusions, but the implications of the main point for the status of thought in animals are fairly crude. If all aspects of human thought, and of human mental states, are interpreted as forms of brain activity, and nothing else, then the only grounds for placing any limitations on animal thought are that brain anatomy, brain chemistry, or brain organisation, are different and inferior in animals. We could thus perhaps dispense with philosophical and psychological analysis altogether, and answer all questions about animal minds by a sufficiently detailed neurophysiological survey. However, there are obvious practical reasons why this would not be enough. For one thing, information about neural organisation, even as far as it can be observed in dead animals, is limited. Scientific knowledge of exactly how brain activity mediates mental processes in either animals or man is even more rudimentary. Few would claim to be able to predict what an awake animal was doing, by studying records of its brain activity obtainable by current techniques; still less what, or if, the animal was thinking.

A second reason for not abandoning all investigation, apart from the scrutiny of brain activities, is that brain-state theories may be wrong, or if not wrong, incomplete. They could be wrong because Descartes was right, or wrong because Popper and Eccles are right, and something else as well as brain activity is necessary for thought. For both practical and theoretical reasons therefore, it is premature to expect that mental states in man or in any other species can be


satisfactorily studied in physiological terms. However, there are few, and they certainly do not include Descartes or Eccles, who would claim that mental states can be accounted for without any reference at all to their physical concomitants.

The possible incompleteness of brain-state theories, even if they are right as far as they go, can be illustrated by the familiar hardware/software distinction in computing. There is certainly a sense in which what computers do is ‘nothing but’ activity in electronic circuits, but the theory of computing and the writing of computer programs are not the same as theories about the electronics. Similarly, how brains work in producing thought may need to be discussed in more abstract terms than brain-state theories immediately suggest. In particular, once we begin to discuss the content of thought or mentation, instead of its general qualities, it may be impractical if not erroneous to enquire too closely as to its physical substrate. To take a very simple example, if we say ‘that dog wants to go for a walk’ we will be more likely to judge the truth of this assertion on the basis of whether or not the dog appeared carrying its leash than on the basis of the state of its brain. Two different dogs may both want to go for walks, we might suppose, without having brains which are in all respects in identical states. More generally, it may be necessary to talk about ideas, or memories, or expectancies, without knowing very much about the relations of these things to particular brains or particular brain states. Popper makes a strong case for a world of ideas in human thought which are in some sense outside brains altogether. ‘In his terms, World I is the brain, World 2 is subjective consciousness, and World 3 contains logical relationships in books, musical scores and other physical products of human societies. The suggestion is that ideas in books ought to be allowed to exist even when no one is reading the books, so that no brains contain the ideas (Popper and Eccles, 1977). This world of ideas is denied to animals, although Popper believes them to have subjective awareness of simpler mental events. However it might be as well to leave open the possibility that logical relationships contained in external reality provide a domain of mental events which may take place in the brains of animals, but which can be considered in isolation from their instances in particular brains, rather as the ideas in Popper’s World 3 provide a psychological category of things outside the human brain. Since, in the external world, bananas grow on trees, we may wish to ask whether chimpanzees have mental representations of bananas and trees. Although it is mainly because the chimpanzee


brain has a great deal in common with the human brain that this question is entertained, we look to behavioural experiments, rather than measurements of brain activity, to answer it.

Perception, memory, abstraction and reason

Descartes has it that animals have no thought, whereas Armstrong (1968), the materialist, suggests that animals may have beliefs, intentions, conscious perceptions and even introspections about their intentions. Thus on one side we have the theory that animals are automata which cannot be said to perceive or remember in the same way that we do, and, on the other, a brain-state theory which implies that there are few limitations on the capacity of animal brains. It is worth pointing out that the relation between animal status and mind- body theories does not have to take this form: it is perfectly possible to be a dualist who believes that animals have immortal souls, or to be a materialist who is convinced that the physical superiority of the human brain is so great as to place an unbridgeable gulf between human and animal capacities. However, Descartes provided the historically important extreme of a dualism which excludes animals, and Armstrong’s brain-state theory gives a clear opposing view. Other opinions are both chronologically and logically stretched out between them. Middling views will of course take the general form of saying that animals can do this, but they can’t do that. By and large, one can keep an ordered scale of perception, memory, abstraction, and reason, and place a theory in terms of how far up this scale animals are put, but there are some exceptions. I shall therefore take philosophical developments in chronological order after Descartes.

Locke(1632—1704): animals have perception, memory and reason but no abstraction

Philosophers after Descartes paid very much less attention to physiology, and concentrated on the mental almost exclusively. This is partly a consequence of Descartes’s assertion that mental states and subjective awareness are primary, even though he himself always insisted that they were intimately intertwined with bodily mechanisms. Assuming the primacy of subjective apprehension of knowledge,


irrespective of physical realities, also meant that the status of animals ceased to be a central concern after Descartes, although, as we shall see, philosophers such as Locke peppered their accounts of the bases of human thought with asides on the extent to which these were shared with other animals.

The main themes of Locke’s psychology are the dependence of knowledge on the accumulation of subjective experiences over time, an emphasis on the interrelating of mental events in the human mind, and an extraordinarily thoroughgoing rejection of the possibility that any aspect of thought depends on preformed innate ideas or inherited determinants of mental states. The theory that knowledge is determined by the accumulation of experience, rather than by innately determined rules, intuitions or revelations, is empiricism. The metaphors used by Locke to illustrate his kind of empiricism include the allusion to the mind’s starting off as a blank tablet (tabula rasa) on which subsequent mental experiences can be written, or as an empty cabinet into which ideas can be placed as they are acquired. One might assume that the cabinet was equipped with shelves or hooks so as better to receive certain sorts of idea if they presented themselves, but it is supposed to remain empty unless anything is actively put in it. The rigour with which Locke adhered to the assumption of the initial emptiness of the mind can be seen by his assertion that the ideas of hunger and warmth come to children only as a result of prenatal experiences in the womb, and his claim that early mental development proceeds ‘according to the divers circumstances of children’s first entertainment in the world’. He supposes that the order in which children acquire ideas will be very variable, depending on the diverse circumstances, and is in any case irrelevant (An Essay Concerning Human Understanding, 1959, p. 185). Modern theories of cognitive development assume a great deal more by way of predetermined sequences of intellectual achievement, and reactions to hunger and warmth at birth are innate if anything is, but this need not detain us.



Perception for Locke is rather a passive process, but involves mental awareness of impressions received from the senses. Animals perceive; indeed, ‘perception puts the difference between animals and vegetables’, although animals with limited sensory apparatus will obviously have dull and obscure perceptions. In fact Locke has perception as such entirely dependent on the quality of the available sense organs.


Cockles and oysters do not need to perceive very much, and do not appear to have much by way of sensory apparatus; we can therefore conclude that, although they are not insensible, their perceptions are exceedingly dull (1959, p. 190). But there is no perceptual gulf between cockles and men, except that due to the effectiveness of peripheral sense organs. Rather pessimistically, Locke suggests that if one becomes sufficiently decrepit in old age as to lose one’s memory, and to be blind and deaf, and to retain little sense of taste and smell, then one’s superiority to a cockle will be a matter of some doubt: ‘How far such a one (notwithstanding all that is boasted of innate principles) is in his knowledge and intellectual faculties above the condition of a cockle or an oyster, I leave to be considered’. And if anyone had the misfortune to have dull senses from birth, ‘I wonder what difference there would be, in any intellectual perfections, between him and the lowest degree of animals’ (1959, pp. 190—1).



Given some conscious perceptions, the next step towards making intelligent use of them requires the retention of sensory information after it has first been received. Locke considers two aspects of retention: first, keeping a simple perception or idea ‘in view’ for some time after it has been initiated, and second, reviving or retrieving a perception from the storehouse or repository of ideas. This distinction, between continuation in a short-term memory or ‘working memory’ as opposed to the retrieval of items from a long-term store is very little altered in current theories (e.g. Gregg, 1975; Baddeley, 1976). Even the hypothesis that we cannot keep ‘in view’ many things at once, and that this is what determines exchanges between the long-term repository and immediate contemplation, appears little changed in the modern concept of limited capacity in short-term memory. As has been rediscovered in the last few years, it is not difficult to find evidence that similar mechanisms operate in animals. ‘Brutes have memory’, says Locke, giving as his example birds which can be seen on one day getting closer and closer to imitating a tune which they heard the day before. This is not a wholly convincing example, but, as Locke says, there are many others, and I shall examine some of them in a later chapter.


Discernment, comparison and compounding

Locke next considers what he calls discerning—there is not much point in having and remembering perceptions if we cannot tell any two of


them apart. It is on improvements in the accuracy of telling perceptions and ideas apart, and on the analysis of clear relations and distinctions between them that human understanding rests, rather than on innate principles: ‘On this faculty of distinguishing one thing from another depends the evidence and certainty of several, even very general, propositions, which have passed for innate truths’ (1959, p. 202). Locke’s theory of knowledge thus rests on something rather like the processes studied under the heading of discrimination learning’ in animals (see chapter 3). However, Locke supposed that the capabilities of animals for the various methods by which improvements in discernment are brought about are limited. One method is the comparison of ideas with respect to such features as time and place, and ‘Brutes compare but imperfectly’ since they probably limit their comparisons to ideas about tangible objects, whereas men compare more abstract and general ideas.

A second quite separate and fundamental operation of the mind is constructing, enlarging and elaborating ideas by the ‘compounding’ and adding together of simpler notions. Again, brutes come far short of man, since, although a dog may use a collection of simple ideas for a single purpose, such as recognising his master by his shape, smell and voice (together or apart), in Locke’s view these elements are not properly compounded by the dog into a single complex idea of his master. In modern terms, the dog might be said to lack adequate facilities for cross-modal comparisons.



The ‘perfect distinction’ between man and beast in Locke’s theory lies in the faculty of abstraction, which is tied to the use of words to represent ideas. Children, once they have some ideas fixed in their memories, ‘begin by degrees to learn the use of signs’ (1959, p. 206). Next, when they have acquired the skill of framing articulate sounds, they begin to use spoken words to communicate their ideas to others. Some of the words they borrow from those already in use, while others the children make up for themselves, ‘as one may observe among the new and unusual names children often give to things in their first use of language’. However, for Locke, the crucial process was not so much in naming itself, as in the subsequent consequences of naming. In order to prevent the growth of an endless list of names for all particular ideas, the mind extracts general features from specific ideas, which serve to identify mental representations of things independently of real existence. The mind then gives general names to these general features—’and


thus universals, whether ideas or terms, are made’. This sounds rather grand, but the example given is a simple one, the possession of the idea of whiteness, independently of its connections with milk, chalk, or snow (1959, p. 207). No animals are thought by Locke to have any capacity for this sort of abstraction, ‘since they have no use of words or any other general signs’. Although the use of words is difficult to assess, it should be pointed out that many animals could easily be trained to push one button whenever they saw anything white, but another button whenever they saw anything that was not white, irrespective of shape of the objects inspected. If detecting whiteness is the paradigm of abstraction, then Locke’s contention, ‘Brutes abstract not’, may be empirically false.



Having established a line between men and animals for abstraction, Locke was quick to disavow a distance of Cartesian proportions between men and beasts. The distance resulting from human abstraction was itself vast, but having already allowed animals perception and memory, Locke specifically adds to these a modicum of reason. Animals have reason, ‘as they have sense’ but can reason only about ideas directly received from their senses, and thus ‘they are the best of them tied up within these narrow bounds’ (1959, p. 208).

We ought at this point to acknowledge that Locke was being notably idiosyncratic in assigning any degree of reasoning to animals at all. The Aristotelian and medieval scholastic tradition was to take reason as the Rubicon uncrossed by animal species, and the convention is retained by most subsequent authorities. Leibniz (1646—1716) picks out Locke’s departure from the norm in his New Essays Concerning Human Understanding, written as a commentary on Locke’s essay, with the main purpose of resisting Locke’s attack on innate ideas, but including agreements and disagreements paragraph by paragraph. Leibniz agrees that there may be connections between one and another ‘imaginations’ in animals, and refers to the case of a dog fearing a whipping when his master takes up a stick. But Leibniz wishes to preserve ‘received usage’ and restrict the term reasoning specifically to human inference. (The apprehensions of dogs reappear intermittently in philosophical texts—recently in Wittgenstein’s characteristically pungent dictum that ‘We say a dog is afraid his master will beat him; but not, he is afraid his master will beat him tomorrow. Why not?’, Philosophical Investigations, para. 650.)


Leibniz concurs with Locke that animals do not form abstract thoughts, but wants to go a lot further than Locke in distinguishing between human perceptions and animal sensations. However, a Germanic hankering for unity in nature seems to persuade Leibniz of a currently obscured organic potential: ‘the animals even, having attained a condition of stupidity, ought some day to return to perceptions more elevated; and, since simple substances always endure, we must not judge eternity by a few years’ (1896, p. 142). Descartes was prepared to consider non-human intelligence within infinite space, rather than eternal time—’I do not on that account infer that there are intelligent creatures in the stars or elsewhere; but I do not see that there are any grounds on which one could prove that there are not’ (Descartes, 1970, p. 295).


Association of ideas

Locke introduced the association of ideas into his system as an afterthought, adding it to the fourth edition of his Essay. He used it to explain mental aberrations, and ‘A degree of madness, found in most men’, not the natural correspondences and connections between ideas which should give rise to true understanding, if a proper use of words is kept to by correct definitions of terms. Locke should not therefore be classed, as he sometimes is, as a supporter of the doctrine of associations as the basis of thought. Hobbes, slightly earlier, and Hume and Hartley, later, made the association of ideas, however their conjunction might occur, a fundamental mechanism; but Locke reserved it for unreasonable connections of ideas ‘not allied by nature’. Conceivably, he was reacting against Hobbes. They were on opposite sides of the seventeenth-century political divide, Hobbes being a Cavalier Royalist, who returned to England with Charles II at the Restoration, while Locke was a Roundhead Parliamentarian, who was eventually forced to take his turn in exile not long after Hobbes came back. Hobbes was also an atheist, while Locke was a Calvinist who spent his last years in biblical scholarship. At any rate, although Locke suggests that the influence of association is generally pervasive, he thought its results were invariably perverse. The supposition that accidental pairings of events cause irrational antipathies, such as aversions to certain foods whose ingestion has accidentally preceded illness, or a dislike of books following painful experiences at school, is congenial to present-day behaviourists, but Locke did go on to discuss the possibility of irrational associations explaining animal learning.


Leibniz, however, did. He seized on the principle of association with great glee, revealing that Hobbes was said to have a phobia for dark places because of their associations with ghosts in stories told to him as a child, even though he did not believe in ghosts. Moreover, the example of the dog afraid of punishment, and all other so-called examples of animal reasoning, as well as irrational human behaviour, could be satisfactorily put down to learned associations (Leibniz, 1896, p. 283). This, written in 1704, must be one of the earliest versions of the associationist view of animal behaviour, taken to its limits in this century by Hull (1943; see chapter 3).

Hume (1711—76): animal inferiority is a matter of degree

Locke had taken Descartes as his model in trying to account for our awareness of knowing by beginning from subjective first principles, and applying a method of doubt. Unlike Descartes he had ignored the question of mind/body interaction (‘I shall not meddle with the physical condition of the mind’), and what he doubted was mainly the possibility of innate ideas. Berkeley (1685—1753) is usually coupled with Locke as a believer in accumulations of subjective experience, and he solved the mind/body problem at a stroke by denying the material existence of the body, or any other physical object: as he thought that the brain, and animals, existed only in the human mind, the question of the function of the animal brain did not arise (1965, p. 172). Hume was in many ways more of a sceptic and a doubter than either Locke or Berkeley, but he did have a good deal to say about animals. Hume did not deny the existence of the material world, but assumed that the method by which our mental intentions acted on the body was ‘unknown and inconceivable’ (1902, p. 67).

In Hume’s work, all human knowledge is divided into two categories, ‘Relations of Ideas’ and ‘Matters of Fact’. Relations of ideas can be made intuitively or demonstrably certain by purely subjective mental activity, without interaction with the external world being necessary, as in the cases of Euclidean geometry and arithmetic—’Propositions of this kind are discoverable by the mere operation of thought, without dependence on what is anywhere in the universe’ (1902, p. 25). Everything else is based on what Hume calls cause and effect, which applies to all cases of deducing one thing from another perceptual experience and to all ‘Matters of Fact’ (1902,


pp. 26-7). All knowledge of this kind of cause and effect depends on experience, and the principle controlling our utilisation of experience is ‘custom’, or ‘habit’. ‘All inferences from experience, therefore, are effects of custom, not of reasoning’, and ‘Without the influence of custom, we should be entirely ignorant of every matter of fact beyond what is immediately present to the memory and senses’ (1902, p. 43 and p. 45). Hume’s scepticism lies in his assertion that we can know no more than our habitual experiences, when it comes to matters of fact. We can say that we have experienced heat and flame together but we cannot thereby assume that one causes the other—we cannot be sure of a ‘necessary connection’ between them. This is a rejection of Locke’s distinction between natural Connections and arbitrary associations. Especially if one has forgone any assistance from innate cognitive organisation, all connections must be equally arbitrary, depending entirely on what past experience happens to have been. This conclusion applies even to apparent certainties, such as the movements of billiard balls. We expect one billiard ball to move when it is struck by another, but our expectation is suspect, if it is induced from prior experience (cf. Popper, 1959).

The implications of this account for human/animal differences may not seem very direct. But it is clear that if, like Leibniz, we have assumed that animal reasoning takes place via arbitrary associations, and then we accept that any distinction between arbitrary and rational associations is invalid, the gap between human and animal inferences from experience will have been considerably narrowed. That there is, in fact, a difference between sorts of association is a current tenet of comparative animal psychology: No associations are arbitrary in practice; particular species are sensitive to particular conjunctions of events; and the human species, apart from having its own preferences, is probably the best species at being arbitrary and unnatural (Hinde and Stevenson-Hinde, 1973). But Hume followed his scepticism about inferences from perception to a consistent conclusion, and we can find his treatment of animal cognition in ‘Of the Reason of Animals’ (Enquiries) and ‘On the Immortality of the Soul’ (Essays).

Although Hume’s description ‘Of the Reason of Animals’ is brief, it is extremely clear, and is worth considering in some detail. First, he reiterates his conviction that all our own reasonings are founded on a kind of analogy, or assessment of similarities—we expect a piece of iron to have certain properties in so far as we have previously observed


other pieces of iron to have them. It follows as a principle of method that the more cases and analogies we can accumulate, the better. In particular, Hume proposes that the comparison of different species of animal is useful in studies of anatomy and physiology, giving the example of the circulation of the blood —we can understand the principle of circulation more thoroughly if it can be observed in fishes and frogs. The same proposal is then stated for psychology: Hume suggests that his theory of human understanding and his theory of the origin of the human passions ‘will acquire additional authority, if we find that the same theory is requisite to explain the same phenomena in all other animals’ (1902, p. 104). This is a surprisingly strong claim for the value of animal psychology, especially as it comes a hundred years before Darwin.

As we might expect, after this claim, Hume finds that his knowledge of animal behaviour requires him to adopt the same principles of explanation which he has previously applied to human cognition, namely the mechanisms of experience and custom. The evidence is drawn both from natural behavioural development in animals, and from the results of training procedures imposed by human intervention:

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.... The ignorance and inexperience of the young are here plainly distinguishable from the cunning and sagacity of the old. . . . 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, and most contrary to their natural instincts and propensities. ... the animal infers some fact beyond what immediately strikes his senses, and this inference is altogether founded on past experience. (1902, p. 104)

On the basis of past experience, animals make inferences, and construct expectations, going beyond the information which is immediately given to them by their senses; but they do not do this because they have reasoned that ‘the course of nature will always be regular in its operations’. Animals are not guided by reasoning, as


philosophers construe it, but then neither are children, neither are most people, in their everyday life, and neither indeed are the philosophers themselves, in their everyday life. Custom, in the form of accumulated experiences and habits, controls the beliefs and imagination of animals and men alike (1902, p. 106).

By discovering a common mechanism, Hume has, to his own satisfaction, strengthened his theory. But if there are common mechanisms underlying human and animal knowledge, what is the source of human superiority? Hume is remarkable for minimising the differences between animals and men, and although he recognises the problem, his solution to it differs from that of almost everyone else, including modern behaviourists such as Skinner, in that he avoids any clear-cut dividing line such as language, abstraction, or imagination, which does not apply as much to individuals within species as to differences between species. His tactic at the end of ‘Of the Reason of Animals’ is to list nine ways in which men can differ from each other, with the implication that exaggerations of these account for the inferiorities of animals. Attention, memory, powers of observation, accuracy of reasoning, the formation of general maxims, the perception of analogies, and ‘many other circumstances’ may affect the understandings of men: similar factors serve to differentiate men from animals. It is also true that animals derive many parts of their knowledge ‘from the original hand of nature’ in the form of instincts, but experimental reasoning, ‘which we possess in common with beasts’, is itself a kind of instinct, and whatever it is that teaches a man to avoid the fire is as much an instinct as the more exact forms which teach a bird ‘the art of incubation, and the whole economy and order of its nursery’.

Hume could hardly have been more definite about the relation between human and animal thought: they are based on the same mechanisms, and human superiorities are a matter of degree. This is a direct contradiction of Descartes, and Hume’s disagreement extended to the question of mind/body interaction, in so far as this entails a consideration of immortality. Hume attempted to demolish logical arguments in favour of the immortality of the soul, although he kept the theological escape route of Divine Revelation. If one has concluded that the mental capacities of animals differ from man’s in only quantitative ways, one of the grounds for drawing moral and eschatological distinctions between men and beasts is removed, and it becomes less obvious that immortality should be reserved for the


human species. One solution, which Aquinas was prepared to consider, but which Descartes was against because of the supposed consequences for public order, is to allow that any arrangements made for the continued existence of human souls may include accommodation for those of animals. These could be simpler that those provided for us, and presumably would not need to be divided between different extremes of comfort, but would not necessarily have to be less durable. However, the tack taken by Hume was that we should assume animals to be mortal, and should therefore have difficulty in establishing anything better for ourselves. ‘The souls of animals are allowed to be mortal; and these bear so near a resemblance to the souls of men, that the analogy from one to the other forms a very strong argument’ (1906, p. 427). Not everyone would agree that this is a strong case, but the use of the argument is a further demonstration, if any is needed, of the lack of distinction between animals and men in Hume’s writing. In even clearer detail, ‘Animals undoubtedly feel, think, love, hate, will and even reason, though in a more imperfect manner than men: are their souls also immaterial and immortal?’ (1906, p. 424).

Hume left his views on immortality to be published after his own death, but the operation of mental and emotional mechanisms in animals was a preoccupation revealed in his earliest work, the Treatise on Human Nature, which he later revised and condensed into the Enquiries. The argument concerning reason is the one most at odds with previous authorities, and the one most likely to be resisted, but it is asserted forcefully, if not crudely, in the Treatise: ‘no truth appears to me more evident, than that beasts are endowed with thought and reason as well as men. The arguments in this case are so obvious, that they never escape even the most stupid and ignorant’ (1888, p. 176). Also included in the Treatise, but omitted from the subsequent condensations, were sections covering ‘Pride and Humility of Animals’ and ‘Love and Hatred of Animals’. The gist is simply that pride and humility, love and hatred, and also fear, anger, courage, grief, envy and malice ‘and other affections’ all exist in animals, and ‘the causes of these passions are likewise much the same in the beast as in us’ (1888, p. 326). The causes are physiological, psychological, and social but ‘these causes operate after the same manner thro’ the whole animal creation’. This is of course an exceptionally strong claim for a common biological base governing human and animal behaviour, matched only by the excesses of current sociobiology (Wilson, 1975). However, Hume was not oblivious to human peculiarities. Pity, for


instance, is not supposed to occur as often in animals as envy and malice, as it requires a greater effort of thought and imagination. And although beasts are susceptible to vices and virtues to the extent of their sense, appetite and will, our superior cognition and understanding immeasurably expand the possibilities of moral distinctions, especially those requiring knowledge of consanguinity and the right of property (1888, p. 326).

A minor theme of the Treatise is thus that human nature is in many ways not to be distinguished from animal nature. Apart from the sections expressly devoted to establishing that the mechanisms governing human psychology are also found in animals, there are places where briefer assertions are made in passing. It seems clear enough from this internal evidence that Hume was deliberate about the disagreement with Descartes, while attempting to build an equally comprehensive account of the human condition. It may not be merely a coincidence that Hume chose to write the Treatise at La Flèche, near Angers, where Descartes had received his Jesuit education. In any event, Hume’s arguments provide an unmissable and vigorous opposition to the Cartesian split between animal automatism and human thought. At the time, Hume’s continuity was at least as agreeable to other writers as Descartes’s dichotomy (see for instance Diderot’s comments made in 1749, ten years after the Treatise and one after the first Enquiry: Diderot, 1916, p. 76), and Hume’s contributions might reasonably be taken as early pioneering along the route taken by Darwinians such as Thomas Huxley; but it is rare to find Hume’s disagreement with Descartes’s dichotomy between men and animals given much weight by later philosophers.

Kant (1724—1804) and Hegel (1770—1831): disappearance of the issue

A retreat from the whole problem of the relation between the human and animal mind was begun by Kant, a towering influence who said virtually nothing on the subject in the course of several monumental books. Kant’s importance for psychology in general is supposed to reside partly in the authority he gave to a preoccupation with the purely mental and spiritual, considered to a large extent as separate from real and physical nature, and partly in his systematic and powerful reassertion of the existence of innate ideas (e.g. Boring, 1950).


Kant claimed that Hume’s first Enquiry awoke him from ‘dogmatic slumbers’: the unpalatability of the conclusions which resulted from Hume’s scepticism was sufficiently stirring to require Kant’s Critiques, but in bringing back nativism, in the form of innate or ‘a priori’ concepts, Kant was also in direct opposition to Locke. There was of course no science of genetics in the eighteenth century, and although Kant wrote on astronomy, meteorology and physical geography, he did not have Hume’s interest in comparative anatomy. The source of ‘a priori’ concepts, as far as Kant was concerned, was thus a matter of spiritual intuition rather than natural inheritance or biological predetermination. But the tradition established by Kant of internal predetermined dimensions of cognition may be seen in both the ‘Gestalt’ psychology of human perception (Kohler, 1929; Kofka, 1935; see Boring, 1950 and Hilgard and Bower, 1975), and in the approach to animal psychology taken by ethologists such as Tinbergen (1951) and Lorenz(1966), who stress the importance of instinctual drives, inherited mechanisms of perception and biologically fixed patterns of movement, in the context of genetic inheritance and evolution.

Kant’s proposal was that human knowledge, and in particular the perception of objects in time and space, depends on inevitable and universal intuitions or concepts, and is not, as the British empiricists held, a product of ‘Pure Reason’ in the sense of associations, rearrangements and inferences which take place partly as a consequence of the circumstances of perception within an individual’s lifetime. Intuition, inspiration and inner feeling are the basis of perceptual and logical categories, including our ideas of relation, existence and cause—and they also ought to be relied on in the course of philosophical speculation. But whether we should assume that similar natural feelings and intuitions occur in animals is another question. Kant was interested in human moral responsibilities towards animals, but apparently on the grounds that an act of cruelty directed at an animal damages the human agent, rather than because of the possible feelings of the victim (‘Duties towards animals and spirits’ in Lectures on Ethics; see Midgley, 1980).

Kant had a teleological view of nature as being organised from the top down, expressing the design and purposes of a Supreme Being. The origin of animals was classed with the secrets of Providence and the mystical number 666 as ‘one of the topics on which ingenuity and thought are occasionally wasted’. And ‘It is indeed quite certain that


we cannot adequately cognise, much less explain, organised beings and their internal possibility, according to mere mechanical principles of nature. . . . We must absolutely deny this insight to men’ (1914, pp. 312—13). It is therefore not surprising that Kant himself spent little time on the details of animal behaviour. However in a footnote to Appendix 90 of the Critique of Judgement, Kant lets slip the conclusion that Descartes was wrong to say that animals are machines. This comes in the course of a discussion of ‘Analogy’ with the example of the construction of dams and nests by beavers, one which may have suggested itself to Kant because of his interest in the inner purposes of rivers. From the similarity of the artificial constructions of beavers to those of men. ‘we can quite rightly conclude according to analogy, that beasts too act in accordance with representations’. But we are not allowed to conclude that because man uses reason to design his buildings, so does the beaver, because the beaver uses instinct instead. The analogy between beast and man in this case is said to work in the same way as the analogy between the works of men and ‘the causality of the supreme World- Cause’: both are doomed to failure (1914, pp. 398—400).

Kant does not doubt that there are ‘things in themselves’ which may be causes of perceptions, even though the qualities and forms of perception are determined by native intuitions. Natural laws and mere mechanisms may be discussed, even though they are subsidiary to subjective reality. ‘Universal principles of the nature of things’ are all right as far as they go, but ‘those principles are simply valid for nature, as an object of sense’ and are not much use when it comes to more important matters, such as ‘the particular concept of a Supersensible Being’. Others after Kant did away with external reality altogether—things need only exist as ideas in a self-conscious mind, if that is going to be the starting point. Hegel begins with self-consciousness and ends with Absolute Knowledge, with physical reality vaguely in between (Phenomenology of Mind). However Hegel is as a rule taken seriously, and a recent commentary suggests that ‘Had Hegel lived in the present age we should now have had a long treatment of the Behaviourisms of Watson and Tolman and Skinner’ (Hegel, 1977). The Hegelian approach can thus be set against behavioural treatments of animal psychology, but also against any strategy which identifies consciousness with physical reality. The Hegelian antidote to brain-state theories, and any form of physiological evidence, ought therefore to be mentioned: ‘Brain fibres and the like, looked at as forms


of the being of the mind, are already, an imagined, a merely hypothetical actuality of the mind’ (1949, p. 371).

Schopenhauer (1788—1860): animals have understanding and will without language

Kant believed that the predetermined constitution of our cognitive faculties means that we can only subjectively understand nature, if we stick to the highest kinds of reasoning, in terms of the designs of a supreme cause, but that subjective understanding is not the same as objective truth. The distinction between subjective understanding and physical reality becomes blurred in Hegel, since reason is reality, and the substance of the universe; and absolute knowledge, or infinite form, sets in motion the infinite material ‘underlying all the natural and spiritual life which it originates’. Organic nature thus conforms to the absolute idea. In Schopenhauer’s adaptation of Kant, however, the idea is subordinate to the will, and the world and all its phenomena can thus be interpreted as objectifications of will. This might not in itself be expected to have immediate implications for animal psychology. It does mean that Schopenhauer has to deal extensively with motives and. volitions, and the workings of motivation in animals are somewhat more accessible than the processes of reason. (Schopenhauer himself coined the term ‘motivation’ in referring generally to motives: e.g. ‘The action of motives (motivation) is causality seen from within’- 1915, p. 171). The fact that Schopenhauer had a lot to say about animals may, however, be partly incidental. He was fond of animals, and had a poodle called ‘World-Soul’ of whose intelligence he was particularly proud, and he was well read in the comparative anatomy and theoretical biology of his day. He was an admirer of ’the excellent Locke’, and therefore addressed the issues of animal capabilities in the same way as Locke and Hume, as well as delivering himself of Kantian metaphysical obscurities.

The most succinct statement of Schopenhauer’s analysis of animal thought appears in ‘On the Irrational Intellect’, in the second volume of his magnum opus, The World as Will and Idea, and his biological theories are contained in the long essay On the Will in Nature. But, like Locke and Hume, Schopenhauer interrupted his discussions of human knowledge with comments on the approximations to such knowledge achieved by domestic pets and lesser organisms in general. He was


more concerned than Hume with the details of the differences between human and animal minds, and few pre- Darwinian writers seem to have had as many things so say about relations between consciousness, memory, comprehension, deliberation and so on, although it must be admitted that consistency and accuracy were not among Schopenhauer’s strong points.

Very explicitly, Schopenhauer claims that we can arrive at ‘a complete knowledge of the consciousness of brutes’, by selecting a limited set of the properties of our own consciousness. This was the view adopted by the later generation of introspective psychologists such as Wundt (1832—1920) and Kulpe (1862—1915), who supposed that some of the information obtained by the new introspective methods used with human subjects could be generalised back to animals, but who differed from earlier philosophers in wishing to conduct quantitative and experimental investigations of human subjective awareness in the first place. For Schopenhauer, the distinction between animals and men does not therefore lie in subjective awareness, but in the traditional mark of reason—’The brute feels and perceives; man, in addition to this thinks and knows: both will’ (1883 vol. 1, p. 47). Animals live in the present, and have intuitive representations, which allow what Schopenhauer calls understanding, to the extent of understanding proper names (1915, p. 117), but are incapable of reflecting on past and future events (in particular their own death), and cannot form ‘abstract conceptions’. Schopenhauer thus follows Locke in making abstraction a specifically human power of thought: the mental states of animals can be characterised as ‘representations’ (perceptions related to objects) but these do not allow human-like thought or knowledge. Schopenhauer accuses even Locke of losing sight of the primary aspect of abstraction, and falling into a wavering account of ‘mangled and derivative manifestations’ of its real inner nature, while Kant ‘confused and falsified’ the true conception of reason and abstraction, and the pitiable Hegel scribbled nonsense and tom-foolery—’three- fourths cash and one-fourth crazy fancies’ —under the heading of an examination of reason.

What is the single essence of reason and abstraction, which others had distorted and mangled? Schopenhauer’s candidate is not original, but his argument is unambiguous and as clear as a bell. ‘It is by the help of language alone that reason accomplishes its most important achievements’. These include social co-operation, civilisation, the


political state, and science and literature, in addition to memory and abstractions (1883, vol. 1, p. 48). All aspects of human reason can “be reduced to what is only possible for abstract, discursive, reflective, mediate knowledge, conditioned by words, and not for mere intuitive, immediate, sensuous knowledge, which belongs to animals also” (1915, p. 130). What distinguishes human thought from animal intelligence is thus language and words, which enable deliberation and reflection, and this classical distinction is only confused by the invention of a ‘completely fictitious’ faculty for metaphysical understanding. Schopenhauer prefers to reserve the term understanding for knowledge of causal laws which are discoverable by perception alone. Animals, even down to the very lowest, use some degree of this sort of understanding, which arises ‘from the habit of seeing one thing follow another’ (1915, p. 89). Clearly, this is a version of Hume, but Schopenhauer suggests that higher animals (mammals) not only have an understanding of learned perceptual associations, but also have a certain amount of a priori knowledge of causality. A young puppy, he says, is reluctant to jump off a table, because it foresees the consequences. Not everyone would accept this, since it tends now to be assumed that young mammals simply have an innate fear of depth, rather than a knowledge of the consequences of falling into depths, but the innate avoidance can reasonably be put down as a predetermined disposition and it may well be the case that the mammalian nervous system is extremely amenable to the formation of rules by which locomotion is linked with being in different places, even if such linkages are normally activated by experience—and this would certainly Count as a Kantian a priori.

The other example of innate knowledge of causality in mammals quoted by Schopenhauer refers to the perplexity exhibited by World-Soul (his poodle) when new curtains were put up in his (Schopenhauer’s) bedroom, of the kind that are drawn apart by a cord. On seeing the curtains open for the first time in the apparent absence of a human agent, the dog spent some time looking for an alternative cause. This is taken to indicate that there is a degree of animal intelligence even in the absence of language. Brutes, however, have only a single intellect, based on direct knowledge, whereas we have a double intellect, verbal reasoning providing the addition of thought, memory, deliberation, and the rest. Only faint traces of these latter faculties, including memory, can according to Schopenhauer be observed in animals, and then only in favoured individuals of the


highest species. Schopenhauer had a special regard for elephants, along with dogs and monkeys representative of the highest species, partly due to his erroneous belief that they have a life-span of 200 years, and therefore a greater opportunity to exercise their inferior form of memory. His interest in animal intelligence was enhanced by his habit of reading English newspapers, and his best elephant story is taken from a report in the Spectator of a coroner’s inquest held in Morpeth on 27 August 1830, at which it was concluded that a keeper, Baptist Bernhard, had been seized and crushed by an elephant in revenge for an offence suffered by the animal two years previously (1883, vol. 2, p. 233).

Resting memory and reasoning mainly on language acknowledges the most obvious separation of man and beast, but also has implications for restrictions on human thinking; and Schopenhauer did not ignore these. He deduced that it is only by learning language that the whole apparatus of human reason is made available. It follows that even badly educated children, as long as they acquire the subtleties of language, possess a form of concrete logic, but the deaf and dumb, unless they receive special training adapted to their condition, should have almost as little of the normal richness of human thought as animals (1915, p. 118). It must also be the case that the properties of human thought and reason depend on precisely what language or languages are available to the individual. This contention is familiar as the Sapir-Whorf hypothesis, which is now in disfavour because of the Chomskean tenet that all languages have an identical underlying structure. Schopenhauer, although he had to contend with the nativist underlying absolutes and universals of Kant and Hegel, was firmly of the opinion that thought depends upon linguistic skills and preconceptions that are acquired by experience. The supposed limitations on knowledge and reasoning in the untutored deaf and dumb are matched by the enhancement of thought in those with a mastery of several (preferably ancient) languages (1883, vol. 2, pp. 238—40, and ‘On language and words’ in Parerga and Paralipomena—’ When one knows many languages, just as many times one is more a man’). The superior structure of Sanskrit, and of Greek and Latin, allows a ‘more perfect construction of thoughts and their connection’, and Schopenhauer was aghast at the contemporary language reforms which involved simplifications in German grammar. He considered a general tendency for languages to become simpler and worse to be powerful evidence against the doctrine of human progress. The


dependency of concepts on words was illustrated by difficulties in the translation of poems and deep or significant prose, Schopenhauer being especially taken by the claim that it was impossible to translate the book of Genesis into Chinese, because of the lack of Chinese terms with which to express the Judeo-Christian concept of a divine creator (1915, p. 367).

If human thought is so much governed by language, then the absence of language in animals should place crushing restrictions on the kinds of thinking that can be attributed to them. Schopenhauer provides a fairly plain alternative to both the dualism of Descartes and the extreme reaction against it by Hume: there is a dichotomy between man and beast, and the differences are not just a matter of degree, but the limitations on thought in otherwise intelligent mammals such as the orang-utan and elephant do not arise from the absence of an immaterial and invisible essence; the limitations may all be put down to a single factor, their comparatively tangible and visible lack of speech.