436b8 About sense and sensing-what it is and why this affection occurs in animals-something was said before in the discussions On the soul.
436b10 Any animal as animal necessarily has sense-power, for by this we determine that something is an animal or non-animal.
436b12 Taking each of them by itself, touch and taste accompany all necessarily, touch for the cause stated in the discussions On the soul, but taste because of food: for by this it distinguishes the pleasant (good-tasting) and unpleasant (bad-tasting) with respect to food, so as to avoid the latter, but pursue the former. And in general, flavor is the affection of the nutritive part of soul.
436b18 But the senses that go through what is external-such as smell, hearing, sight-are in those of them that advance. And they are in all that have them because of health, so that, pre-sensing, they might pursue food, but avoid what is bad and harmful.
437a1 And they are in those that have prudence for the sake of the "well": for they announce many differences, from which there arises in them discernment of what can be contemplated and what can be done.
437a3 Of these, sight is better for what is necessary and of itself, but hearing for understanding and by accident.
437a5 For the power of sight announces many and many kinds of differences, because all bodies participate in color. Hence the common objects are also better perceived by this; I call size, shape, movement, and number "common." But hearing announces only differences of sound, but to a few also those of voice.
437a11 But by accident hearing contributes a greater share to prudence. For discussion, being audible, is a cause of learning, not in itself, but by accident; for it consists of words, and each of the words is a symbol. Hence of those deprived from birth of one of the two senses, the blind are wiser than deaf-mutes.
437a18 The power that each sense has has now been discussed.
436b8 Having presented a prologue in which he has shown his intention, here the Philosopher begins to follow up his proposal.
First he determines about what pertains to the external sense-power. Second he determines about certain things pertaining to inner sensitive cognition, namely memory and recollection, where he says About memory and remembering (449b4); for the treatise On memory and recollection is part of the present book according to the Greeks.
On the first point he does three things. First he takes up some things that were said about the sense-power in the book On the soul and that are to be used as suppositions, as was said above. Second, he determines the truth that he intends about the workings of the senses and of sensible objects, where he says At present some inquire (Chapter 2, 437a19). Third, he solves certain difficulties about the foregoing, where he says But someone will raise an objection (Chapter 14, 445b3).
On the first point he does two things. First he states what was said about the sense-power in the book On the soul. Second he takes up some of these points, where he says Any animal as animal (436b10).
Accordingly he first says that in the book On the soul, something was said about sense and sensing-that is, about the sensitive power and its act. Two things were said about them, namely what each of them is, and the cause why they occur in animals. He calls sensing an "affection" (passio) because the action of sense comes about in a being-affected (paciendo), as was proved in On the Soul II. Near the end of On the Soul II he showed what sense is and why animals sense by the fact that animals are able to receive the forms of sensible things without matter.
436b10 Then, when he says Any animal as animal, he takes up three things that were said about sense in the book On the Soul. The first pertains to sense in general. The second pertains to the senses that are common to all animals; he takes this up where he says Taking each of them by itself (436b12). The third pertains to the other senses, which are found in perfect animals; he takes this up where he says But the senses that go through what is external (436b18).
Accordingly he first says that every animal, inasmuch as it is animal, necessarily has some sense-power: for the nature (ratio) of animal, by which it is distinguished from what is non-animal, consists in its being sensitive.
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The reason is this. An animal reaches the lowest level of knowing things, which surpass things that lack knowledge by being able to contain several beings in themselves, by which their power is shown to be more open and to extend to more things. And inasmuch as a knower has a more universal grasp of things, its power is more absolute, immaterial, and perfect. Now the sensitive power that is in animals is certainly open to what is outside, but only in the singular. Hence it also has an immateriality inasmuch as it is receptive of forms of sensible things without matter, but it has the lowest immateriality in the order of knowers, inasmuch as it can receive these forms only in a bodily organ.
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436b12 Then, when he says Taking each of them by itself, he presents what pertains to the senses that are common and necessary to animals.
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On this point it must be considered that the senses that are common and necessary to every animal are those that apprehend what is necessary to an animal. Now there are two ways in which something sensible is necessary to an animal: in one way inasmuch as the animal is a mixed body, composed of the four elements, and thus there is necessary to it the required balance of hot and cold, moist and dry, and other such differences of mixed bodies; and something else is necessary to the animal inasmuch as its body is a living thing capable of being nourished, and thus suitable food is necessary to it. By the contraries of these an animal is destroyed. And although the first is necessary to every mixed body, and the second is also necessary to plants, an animal has something more than these in being able to have knowledge of what is necessary, for the reason already stated, according to the level of its nature. Accordingly, in order for it to apprehend what is necessary or harmful to it according to its nature (ratio) as a mixed body, it has the sense of touch, which apprehends the above-mentioned differences; and in order for it to apprehend suitable nourishment, the sense of taste is necessary to it, by which it apprehends what tastes good and bad, which are signs of suitable and unsuitable nourishment.
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This is why he says that touch and taste necessarily accompany all animals. Concerning touch, the cause was given in the book On the soul, namely that touch is cognitive of the things of which an animal is composed. But taste is necessary to an animal because of food, because by taste an animal distinguishes the pleasant and unpleasant, or good-tasting and bad-tasting, in food, so as to pursue one of these as suitable and avoid the other as harmful. And flavor as a whole is the affection of the nutritive part of soul-not that it is the object of the nutritive power, but that it is directed to the act of the nutritive power as its end, as was said.
But Alexander says in the commentary that in some manuscripts in Greek the text reads: "flavor is the affection of the tasting part of the nutritive part of the soul." For flavor is apprehended by taste, which is ordered to nourishment.
436b18 Then when he says But the senses that go through what is external, he follows up on the senses that are only in perfect animals.
First he gives the general cause of these senses being in all animals of this kind. Second he gives the special cause of their being in the more perfect of them, where he says And they are in those that have prudence (437a1).
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On the first point it must be known that animals are called "perfect" in which there is not merely a sensitive part without forward movement, as in oysters, but which in addition have a moving part with respect to forward movement. And it must be considered that such animals surpass imperfect, that is, immobile animals as the latter surpass plants and other mixed bodies: for plants and inanimate bodies have no awareness of what is necessary to them; immobile animals have knowledge of what is necessary only inasmuch as it is immediately presented to them; but forward-moving animals also receive knowledge of what is necessary from a distance, and so they more closely approach intellectual knowledge, which is not confined to the here and now.
And just as in all animals taste is ordered to knowing the necessary pertaining to nourishment inasmuch as it is immediately presented, so smell is ordered to knowing it from a distance as well. For odor and flavor have an affinity, as will be said below, and just as by flavor the suitability of food taken in is known, so by odor the suitability of food at a distance is known. But the other two senses, sight and hearing, are ordered to knowing from a distance everything necessary or harmful to an animal, whether in its nature (ratio) as a mixed body or in its nature as a living body capable of being nourished, for it is clear that by sight and hearing animals avoid whatever is harmful and pursue what is healthy.
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And so he says that the senses that are actualized through external media, as was said in On the Soul II, namely smell, hearing, and sight, are in those among the animals that advance-that is, move with forward movement-in all of them for one general cause, namely because of health-that is, so that they might know what is necessary from a distance, just as by taste and touch they know it when present. And he adds: so that, pre-sensing-that is, sensing from a distance-they might pursue suitable food and avoid whatever is bad and harmful. For instance, a sheep flees a wolf as something harmful, but a wolf pursues a sheep that is seen, heard, or smelled, as suitable food.
437a1 Then, when he says And they are in those that have prudence, he gives another, specific cause why these senses are in some more perfect animals.
First he presents this cause. Second he compares the senses with reference to the causes mentioned, where he says Of these, sight is better (437a3).
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On the first point it must be considered that prudence is directive in what is to be done. Universal prudence is directive with respect to anything to be done whatsoever, and so it is in none of the animals except human beings, who have reason, which is able to know universals. But there are certain particular prudences in other animals for certain predetermined acts, for instance in the ant, which in summer gathers food on which it lives in winter.
Now the above-mentioned senses, but especially hearing and sight, are advantageous to animals for particular prudences of this kind, and to human beings for universal prudence, in order that something might be done well. But smell seems to be wholly subservient to the need for nourishment, and not at all to prudence, and so this sense is extremely weak in all those who have perfect prudence, as is said in the book On the soul.
He shows how the above-mentioned senses serve prudence by the fact that they show many differences among things, from which the human being goes on to discern what can be contemplated and what can be done. For by sensible effects the human being is raised to consideration of what is intelligible and universal; and also by what is sensible-that is, by what he has heard and seen-he is instructed about what is to be done. Other animals do not participate in any contemplation, although they do participate in action in a particular way, as is said in Ethics X.
These two senses announce many differences because their objects are found in bodies as consequences of what is common to all bodies, both lower and higher. For color is a consequence of light and the transparent (dyaphanum), which lower bodies have in common with the heavenly body; and sound is a consequence of local movement, which is also found in both kinds of body. But odor is a consequence only of the mixed bodies by which an animal is naturally nourished.
437a3 Then, when he says But of these, sight is better, he compares sight and hearing with reference to the above-mentioned causes.
First he presents the comparison. Second he proves it, where he says For the power of sight (437a5).
On the first point he says that sight surpasses hearing in two ways. In one way with respect to what is necessary, for instance in seeking food and avoiding what is harmful, things that are apprehended with more certainty by sight, which is altered by things themselves, than by hearing, which is altered by sounds, which are consequences of the movements of some things. In another way sight is also of itself superior to hearing, because it is more able to know, and able to know more things, than is hearing. But hearing surpasses sight inasmuch as it serves understanding, although this is by accident, as will be shown below.
437a5 Then he clarifies what he said, where he says For the power of sight announces.
First that sight is in itself better. Second that hearing is better accidentally, where he says But by accident hearing contributes (437a11).
Accordingly he first says that sight is in itself better because the power of sight by its apprehension announces to us many differences among things and among various kinds of things. This is because its object, which is the visible, is found in all bodies: for a thing becomes visible by the transparent being illuminated in actuality by a shining body, and the lower bodies have this in common with the higher ones. And so he says that all bodies participate in color, the higher as well as the lower ones, because in all bodies either there is color itself in its proper nature (ratio), in the case of bodies in which there is a bounded transparent; or there are at least the principles of color, which are the transparent and light. And so more things are manifested by sight than by hearing.
Also, the common sensibles are better known by this sense, because inasmuch as sight has a power of knowing that is more universal and extends to more things, it is more effective in knowing, because the more universal any power is, the more powerful it is. And those are called "common" sensibles that are known not by one sense only, as are the proper sensibles, but by several, for instance size, shape, movement, and number. For the qualities that are the proper objects of the senses are forms in a continuum, and so the continuum itself, inasmuch as it is the subject of these qualities, must move the sense-power not accidentally, but as the per se and common subject of all sensible qualities. And all the so-called common sensibles do in some way pertain to the continuum: whether with respect to measurement of it, in the case of size; or with respect to division of it, in the case of number; or with respect to limitation of it, in the case of shape; or with respect to distance and nearness, in the case of motion.
But hearing announces to us only differences among sounds, which are not found in all bodies, and are not expressive of the many diversities of things. But to a few animals hearing does show differences of voice. Voice is sound projected with an imagining from an animal's mouth, as is said in On the soul II, and so the voice of an animal as such naturally indicates the animal's inner feeling (passio), as the barking of dogs indicates their anger. Thus the more perfect animals know one another's inner feelings from voices, a knowledge that is not in imperfect animals.
Excerpted from Commentaries on Aristotle's On Sense and What Is Sensed and On Memory and Recollectionby THOMAS AQUINAS Copyright © 2005 by The Catholic University of America Press. Excerpted by permission.
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