Chapter IV -- 7
St Thomas distinguishes five genera (main kinds) of powers of the human soul: the vegetative, sensitive, appetitive, locomotive and intellectual.
Since we will not otherwise discuss the locomotive power of the soul except implicitly when we discuss St Thomas’ theory of action, let us remark here that it is the power of the human to move from place to place, which power the soul shares with the (perfect) animals.
It should be understood here that St Thomas is adopting the full Aristotelian model of human psychology, and that, while Aristotle included the faculties (mind, temper and desire) that his master, Plato, defined, his model is more complex, including other faculties. Hence, we encounter in St Thomas—and even in St John of Damascus, another Aristotelian—faculties of the human soul that are not addressed by St Gregory of Nyssa or St Augustine, who give a more Platonic account of human psychology.
St Thomas divides the vegetative powers of the soul into the nutritive, augmentative and generative powers. These are merely the three main functions of plants that even St Macrina alluded to in her adaptation of Aristotelian psychology to the Genesis account of creation. Plants maintain themselves by taking in nourishment through their roots and by completing its processing in their leaves and fruit; they grow larger; they reproduce themselves by means of their seeds. These three powers are common to all living things on the face of the earth: plants, animals and men. Even viruses in some fashion manifest these three powers.
St Thomas then turns to the sensitive powers of the soul. He first distinguishes the five external senses: sight, hearing, smell, taste and touch. These are obvious. Man possesses these five external senses in common with the higher animals, even if many of the lower animals do not possess all of them in fullness.
In an important development, St Thomas distinguishes, still discussing the sensitive or animal powers of the soul, four separate internal senses of the soul: the ‘common sense’, the ‘fantasy’, the ‘estimative power’ and the ‘memorative power’. It must be emphasized that, for St Thomas, following Aristotle, these four internal senses are related to the sensitive or perceptual powers of the soul and have nothing to do with the spiritual senses that in Chapter III we encountered in the Kephalaia Gnostica of Evagrius Pontikos or that we will encounter in Chapter V. They arise from Aristotle’s and St Thomas’ analyses of how humans and animals perceive and act on their perceptions. It is well to spend some time on these internal senses, for they are important.
The common sense has nothing to do with prudence. It works in this way: Let us suppose that we have before us a man who is speaking. Then by means of our external sense of sight we have a visual sense-perception of the man, and by means of our external sense of hearing we have an auricular sense-perception of his speech. But we do not experience in our consciousness two separate, unconnected sense-perceptions: the one, the sight of the man (a visual perception); the other, the sound of the man speaking (an auricular perception). We have a unified sense-perception of a man speaking. It is the common sense which integrates the disparate perceptions of a single object that we have by means of various sense organs into a single, unified sense-perception of the object: our integrated perception of the man speaking.
Moreover, this common sense judges not only the perceptions that we receive by means of the sense organs in the way just explained, but also judges the senses themselves. As St Thomas remarks, a man sees that he sees, but this cannot be due to the eye: the sense organ receives only the sense impression of the object, by which sense impression the organ is modified. The common sense, however, both receives the sense impression of the object and judges the sense itself. It therefore both sees the object and sees the seeing, and that is how a man sees that he sees. This seems to be St Thomas’ approach to the modern concept of ‘consciousness’, for is not our experience of consciousness the perception we have of perceiving? Later, St Thomas will make a similar comment concerning the reflexive act of the intellect by which we know that we know, and it might be remarked that consciousness is also the knowledge we have of knowing. Perceiving and knowing are sharply distinguished in St Thomas.
The fantasy, or imagination, has nothing to do with what today we consider fantasy. It is a technical term in Aristotelian and Thomist psychology that has to do with the retention by the soul of a perception of an object of sense. For the object itself does not enter the soul. The external sense organ is modified and the common sense receives a sense-perception. That sense impression is then retained in the fantasy or imagination. For, St Thomas remarks, an animal can be set in motion to seek what is not present, but this would not be possible if the animal could no longer represent to itself that which was once perceived but no longer present. This is the function of the fantasy or imagination: it is a storehouse of sense-perceptions.
When we experience a spontaneous image in our ‘mind’s eye’, that image comes out of this storehouse. This is the connection of the Thomist concept of fantasy to our modern everyday sense of the word: the content of our daydream is taken from the storehouse of fantasy in the Aristotelian and Thomist sense.
It might be remarked that the reader could best understand these powers of the soul that St Thomas, following Aristotle, delineates, as things the soul can do: it would be fruitless to look for a location in the soul for each of these powers. However, since the particular functions of the human soul here being described are on St Thomas’ own account directly dependent on the body, his analysis of them should be reformable on the basis of findings in neurophysiology.
The next power is the estimative power. Here it must be recalled that, since St Thomas is discussing the animal or sensitive soul, he must account for perception not only in man but also in animals, which on his account lack reason. Moreover, although St Thomas takes for granted that the animal is attracted to the pleasurable sense impression and repelled by the disagreeable sense impression, he also wishes to address the cases where the animal avoids certain things because they are harmful and makes use of certain things because they are useful. This notion of the useful and the harmful he has taken from St Augustine. St Thomas is therefore obliged to consider the following sort of case: the lamb, when it sees the wolf, flees. We are reminded of the experiment of a modern ethologist which established that newborn chicks immediately fled the shadow of a hawk but not the shadow of a harmless bird. It is this sort of thing that St Thomas is addressing: how is it that animals which lack reason have instinctive reactions to immediate sense-perceptions, which reactions neither are governed by reason nor remain at the level of the ‘stimulus – response’ (pleasure – pain) model of behavioural psychology? For, St Thomas wants us to understand, it is not that the lamb is frightened by the size or the greyness of the wolf taken as raw sense data. Rather, St Thomas says, the lamb sees in the very wolf itself the enemy of its kind. Similarly, in the modern experiment with the chicks, it was not the mere passing of shadow over the chick which caused the chick to flee, but the passing of shadow as cast by a (dummy) hawk, as was indicated by the fact that the passing of shadow as cast by a harmless bird did not cause the chick to flee.
Moreover, St Thomas is also addressing this sort of thing: how it is that birds build their nests? For, he says, it is not merely at the level of specific sense-perceptions that are pleasurable or painful that a bird builds its nest, for the bird does not collect straw for its nest on account of the pleasure that that activity gives it, but because the straw is useful to the construction of the nest. As we ourselves remarked in Chapter I, the bird also is able to judge that its nest is damaged and to repair it, and moreover to build and to repair it according to the standard model of the nest of the species to which the bird belongs.
However, St Thomas’ notion of this estimative power is quite narrow:
However, the imperfect knowledge of the end is this, that it consists in the sole apprehension [i.e. perception] of the end, without the nature (ratio) of the end being known, nor the relation of the act to the end; and this sort of knowledge of the end is found among the brute animals by their sense-perception and their natural estimative power.
What St Thomas means is this: The animal really does not understand the end for which it is acting, nor the relation of its means to its ends. Its actions are instinctual, based both on sense-perception and on this natural estimative power. This is essential for St Thomas to assert since according to him only humans possess reason at all—what we can call the powers of abstraction and ratiocination. However, obviously from common experience in an age where men even in the cities lived far closer to nature than ordinary men in the countryside live today, St Thomas wants to account for the purposeful behaviour of animals: he does not believe that a full account of animal behaviour can be given by a theory of animal behaviours based merely on pleasure and pain. Hence his assertion that the animal does not have a rational comprehension of the nature of the end for which it is acting, nor of the relations of its means and its ends, although it does apprehend the end imperfectly: the bird collects straw for its nest without apprehending rationally either that the straw is for its nest or that it is building a nest so that it can raise its brood of chicks; its apprehension is limited to its sense-perception and to the ‘understanding’ that this estimative power provides.
Does this doctrine accord with St Thomas’ own example of the bird collecting straw for its nest? For surely there is an instinctual comprehension in the bird of the relation of the straw-collecting activity (the means) to the nest (the end). Moreover, the bird understands that the nest is damaged and repairs it according to the standard model of its species. For St Thomas’ theory to be valid, the estimative power must provide something more than sense-perception and automatic behaviours, even if it provides less than rational comprehension of the end and the means to that end.
St Thomas is of course addressing the issue of animal instinct. Indeed, the ‘estimative power’ is sometimes translated the ‘instinctive power’.
It is well to note that St Thomas is addressing instinct within the framework solely of what is ‘harmful’ or ‘useful’ to the animal. We ourselves wonder why St Thomas restricted himself to that single polarity: surely there are other axes of instinctual judgement both in animals and in man. St Augustine provided St Thomas with the basic polarity. But St Augustine was not such a rigid thinker as by that to exclude other possibilities.
The migratory habits of birds are an example of an axis of instinctual judgement that cannot easily be reduced just to the harmful and to the useful.
Moreover, as we ourselves have often observed, when the swift flying at full power in a random trajectory in front of the monastery returns to the hole in the monastery wall where its nest is, it approaches the wall at full power and, without hesitation or confusion, arrives precisely at the right hole and enters. The swift’s level of spatial comprehension seems to be very high indeed.
Moreover, as we ourselves have noticed, animals respond to love even when that love is not exhibited towards them in any obvious way at all that a behavioural psychologist could adduce as an example of behavioural conditioning. For example, a monk was caring for an injured dog; certain other animals approached while he was doing so: they responded to his love, even though that love was not expressed towards them at all.
That this is important for an understanding of the nature of animal intelligence can be seen in vignettes from the lives of the saints. In one, St Makarios the Alexandrian (4th C.) was approached by a hyena who bore with her, her blind pup: she placed the pup at his feet and waited. By his prayers St Makarios healed the pup of its blindness and restored it to its mother.
St Savas (439–532) was resting in a lion’s cave in the desert. When the lion returned, it with great respect and gentleness dragged him out of its lair; and when St Savas insisted on remaining, the lion gave up and sought out another lair.
When St Gerasimos (5th–6th C.) removed the thorn from the foot of the lion, the lion became his life-long friend and companion.
But it might also be remarked that the revelations of the ethology of the Twentieth Century were already old hat in the Thirteenth.
The Thomist concept of the estimative power of the animal might be useful in the evaluation of research into and experiments concerning animal intelligence. For as we ourselves understand what St Thomas is saying, the use, say, of a stick by the chimpanzee to obtain the honey or insects in the tree, or the similar use of primitive tools by other animals, might be construed to be a matter of this estimative power.
Experiments into the teaching of language to chimpanzees and other higher apes might also be susceptible of evaluation in the light of St Thomas’ notion: the issue would be the extent to which the ape that had learned the primitive language was not merely exhibiting this estimative power—instinctual intelligence—but also an actual capacity for abstract intelligence. The researchers, as we understand their work, want to say that as primitive as the language is that they have taught to the ape, it nevertheless exhibits all the necessary characteristics of human language, including abstract intelligence. However, a critical look at the evidence would raise the question: is not what is being exhibited this estimative power and not human intelligence?
German shepherd dogs exhibit a high degree of intelligence which nonetheless must be considered the sort of thing called the estimative power by St Thomas. Once we ourselves blocked the road to the monastery to a stray dog, not even a German shepherd, and did not allow it to pass. The stray, which had already visited the monastery, descended into the gully below the road and, very clearly exhibiting intelligence—and even St Thomas’ memorative power, since the dog obviously was intent on proceeding along a road which led only to the monastery—, searched for a passage around us. But surely this is the estimative power that St Thomas is discussing.
Moreover, when local wolves pack when it snows—and only when it snows—in order to attack our mules, they attack the mules as a team, not as a mob. They very clearly have an articulated instinctual attack strategy. That they pack in this way only when it snows is suggestive that the whiteness of the snow triggers an instinctual program. Of course, wolves have since been eliminated on Mount Athos. Our point is that the wolf exhibits an ability to communicate and to work in concert with its pack-mates in an organized activity which manifests role differentiation. The language that the chimpanzee is alleged to have learned might be evaluated in this light: to what extent is the language learned merely a manifestation of the instinctual power of a social animal, a power that remains at the level of the estimative power of St Thomas and does not attain to human intelligence?
As we ourselves understand the doctrine of epiphenomenalism, especially as it is propounded—not by the name of epiphenomenalism, certainly—in Monod’s Le hasard et la nécessité what is asserted is that human intelligence (the reason or intellect of
What St Thomas says is that the animal soul has a separate judgemental power—this estimative power—which enables the animal to evaluate the meanings (intentiones) of particular sense-perceptions in the way we have discussed. Moreover, these meanings have to do with whether the thing perceived is harmful or useful to the animal (hence St Thomas’ two examples: the lamb fleeing the wolf; the bird collecting straw for the nest). Since, according to St Thomas, the animal lacks reason, this estimative power cannot operate on universals—the general abstract characteristics of objects—because that is a function of reason. This estimative or instinctive power works on particular or individual sense-perceptions, discerning a meaning to the particular sense-perception: whether the object perceived is harmful or useful.
In the case of man, St Thomas somewhat modifies his treatment of the estimative power. For although he grants that sense-perception in the animal and in man is the same, he asserts that the estimative power is somewhat different in man: In the animal, the judgement by the estimative power of the meaning—‘harmful’ or ‘useful’—of a sense-perception is the result of a natural instinct. In man that judgement is made on the basis of a comparison of ‘meanings (intentiones)’, but meanings which remain at the level of particular sense-perceptions, meanings which do not attain to the level of abstract reason.
In man, the estimative power is called by St Thomas the ‘particular judgement’. The reader may recall from earlier in our presentation that St Thomas remarked that the doctors of his time assigned the particular judgement to the mid-part of the head. That St Thomas can accept this point of view indicates clearly that he considers the particular judgement to be a power of the sensitive or animal soul, that is, a power which does not at all implicate the reason or intellect, which, according to St Thomas, operates without any reference to the body at all. St Thomas asserts that in man the particular judgement compares individual meanings (those related to individual sense-perceptions) whereas the reason has as its task the comprehension and comparison of universals or concepts.
The difference might be exemplified as follows: the particular judgement, a power of the sensitive soul that is located in the mid-brain, recognizes that the tiger crouching before me is a danger, and that not merely on account of its stripes and colour and shape, but on account of a meaning that I grasp associated with the sense-perception and that arises from a comparison with other meanings. However, my reason, an intelligible power of the soul not located in the brain, understands that the animal is a tiger, a member of the cat family, and that it is different, within the cat family, from the lion, and, outside the cat family, from the wolf and the other members of the dog family.
The issue in questions of animal intelligence is whether the animal—even the chimpanzee or gorilla which has been taught an artificial language—ever passes from instinctual meaning—that the tiger is a danger, that the stick is useful—to abstract intelligence: what sort of thing the tiger is; what sort of tree it is from which it has taken the stick; and, St Thomas says, what the nature of the end is and what the relation is of the means to the end.
The final internal sense is the memorative power. St Thomas distinguishes between the fantasy and the memorative power in the following way: The fantasy retains simple perceptions of objects of sense, which perceptions have been imprinted from without. The memorative power contains meanings produced by the estimative power or, in man, the particular judgement, which meanings arise from within the soul of the animal or man. Since meanings of the harmful or useful are involved which are not simple sense-perceptions and which therefore cannot be sense-perceptions stored in the fantasy, the memorative power must necessarily be different from the fantasy. However, the sense-perceptions that are recalled by the memorative power are originally stored in the fantasy.
St Thomas observes that in man the memorative power requires an active effort called ‘reminiscence’, whereas in the animal a spontaneous activity brings forth the sense impression stored in the fantasy. Moreover, St Thomas observes, in the cases both of the animal and of man, the remembered sense-perception bears the character of a past occurrence, something impossible for a simple sense-perception to bear by itself, something, therefore, that cannot be stored in the fantasy.
Here it is well to consider that the powers of the soul that St Thomas is describing are best understood as arising from his logical analysis of the sorts of things that men and animals do: it would be fruitless to look for the location of these faculties, although, as we have already remarked, St Thomas’ analysis of the powers of the sensitive soul should be reformable on the basis of the findings of neurophysiology.
It should be remarked that the memorative power is what today we would ordinarily understand by the memory. It is the memorative power that looks to the past, to the pastness of a thing. St Thomas later posits the existence of a faculty called the ‘memory’, different from the memorative power. The ‘memory’ is not at all the same thing as the memorative power. For St Thomas later asserts that the ‘memory’ is the same as the intellect. But the intellect is the seat of reason and, as we have seen, has no connection with the body at all, whereas the memorative power, being a function of the sensitive soul, necessarily depends on the body. St Thomas’ ‘memory’ has certain functions in cognition which have nothing to do with the pastness of an event.
 ST Ia, 78. In what follows ‘soul’ always refers to the human soul, unless otherwise indicated.
 ST Ia, 78, 1.
 ST Ia, 78, 2. These powers, of course, correspond to the Aristotelian vegetative soul or, intuitively, to what we observe in the higher plants.
 ST Ia, 78, 3. These powers of course correspond to the Aristotelian animal soul.
 ST Ia, 78, 4.
 ST Ia, 78, 4, ad 2.
 This is obvious to anyone who has had a pet dog.
 The basis of the ‘conditioning’ of behavioural psychology.
 ST Ia, 78, 4.
 ST Ia IIae, 6, 2.
 As it is understood by Fr Copleston himself, surely.
 Here, St Thomas evidently means that I have had similar experiences with other animals.
 See Gilson E pp. 230–1.