Prologue — Prologue

Since it was determined about soul in itself, and each virtue from the point of view of it, the next thing is to make a consideration about animals, and everything that has life, as to what are their proper and what their common operations. Accordingly, let the things that were said about soul be underlying, and let us speak about the rest, and first about what is first.

The greatest both of the common and of the proper features of animals are seen to be common to both body and soul.

For instance, sense and memory, and anger and desire, and appetite as a whole, and with these pleasure and pain. For almost all of these are present in all animals. And with these, some things that are common to everything that participates in life, and some to some of the animals. Of these, the greatest are four pairs in number, namely wakefulness and sleep, and youth and old age, and inhalation and exhalation, and life and death. About these it must be considered what each of them is and for what causes it occurs. But it also belongs to the student of nature to discover first principles concerning health and sickness.

For it is impossible for either health or sickness to occur in what lacks life. Therefore, in general, in the case of most students of nature, and of the physicians who pursue the art more philosophically, the former finish with what belongs to medicine, but the latter begin medicine with what belongs to nature.

That all the abovementioned are common to soul and body is not unclear. For with respect to all, some take place together with the sense power, some through the sense power. And with respect to certain ones, some exist as affections of it, some as conditions, some as protections and benefits, and some as destructions and privations. And that sense is present in the soul by means of the body is clear both through discussion and apart from discussion.

1. As the Philosopher says in On the Soul 3, just as things are separable from matter, so also is what pertains to intellect. (Aristotle, On the Soul 3.4, 429b21–22; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 2, n. 716.) For everything is intelligible inasmuch as it is separable from matter. Hence what is by nature separate from matter is of its very self intelligible in actuality; but what is abstracted by us from conditions of matter is made intelligible in actuality by the light of our agent intellect. And because the habits of a power are specifically distinguished according to differentiation of that which is the per se object of the power, the habits of the sciences, by which intellect is perfected, are necessarily distinguished according to differentiation of the separable from matter, and so the Philosopher in Metaphysics 6 (Aristotle, Metaphysics 6.1, 1025b3–1026a32; cf. Aquinas, Commentary on Metaphysics, bk. 6, lect. 1, nn. 1144–70.) distinguishes genera of science according to different manners of separation from matter: what is separate from matter according to being and nature pertains to the metaphysician; what is separate from matter according to nature and not according to being pertains to the mathematician; and what includes sensible matter in its nature pertains to the natural philosopher.

2. And just as different genera of science are distinguished according as things are in different ways separable from matter, so also in individual sciences, and especially in natural science, the parts of a science are distinguished according to different manners of separation and concretion. And because universals are more separate from matter, in natural science one proceeds from universals to what is less universal, as the Philosopher teaches in Physics 1. (Aristotle, Physics 1.1, 184a23–24; cf. Aquinas, Commentary on Physics, bk. 1, lect. 1.) And so he began the teaching of natural science with what is most common to all natural things, namely movement and principles of movement, and from there proceeded by way of concretion or application of common principles, to determinate mobile things, some of which are living bodies.

Concerning these he also proceeded in a similar way, dividing this consideration into three parts.

First, he considered soul in itself, in an abstraction, as it were;

second, he has a consideration of what belongs to soul according to a concretion or application to body, but in general;

third, he has a consideration that applies all this to individual species of animals and plants, determining what is proper to each species.

Thus, the first consideration is contained in the book On the Soul;

the third consideration is contained in books that he wrote on animals and plants; (See, for example, History of Animals, Parts of Animals, and On the Generation of Animals, referred to by Aquinas under the title De animalibus.)

the intermediate consideration is contained in books that he wrote on some things that pertain in common either to all animals, or to several kinds of them, or even to all living things, and the present intention involves these books.

3. Hence it must be considered that in On the Soul 2 (Aristotle, On the Soul 2.2; Cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 3, nn. 255, 260; lect. 5, n. 287.) Aristotle determined four levels of living things.

The first consists of those that have only the nutritive part of soul, by which they are alive, namely plants.

But there are some living things that, together with this, also have a sense power but without progressive movement, namely imperfect animals, for instance shellfish.

And there are some that have in addition forward local movement, namely perfect animals such as the horse and the cow.

And some in addition have intellect, namely human beings. For although the appetitive part is held to be a fifth genus of powers of soul, it does not constitute a fifth level of living things, because it always accompanies the sensitive part.

4. Now among these powers, intellect is the actuality of no part of a body, as is proved in On the Soul 3, (Aristotle, On the Soul 2.1, 413a7; 3.4, 429a18–b5; 3.5, 430a17–18; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 1, nn. 671–99.) and so it cannot be considered by a concretion or application to a body or to any bodily organ, for its greatest concretion is in soul and its highest abstraction is in separate substances. This is why Aristotle did not write, in addition to the book On the Soul, a book On Intellect and the Intelligible, but if he had done so, it would not pertain to natural science, but rather metaphysics, to which consideration of separate substances belongs. But all other parts of soul are actualities of parts of a body, and so there can be a special consideration of them by application to a body or bodily organs beyond the consideration made of them in the book On the Soul. (Aristotle, On the Soul 2.3–3.3; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 6–30, nn. 299–670.)

5. Accordingly, this intermediate consideration must be divided into three parts.

One includes what pertains to a living thing inasmuch as it is living. This is contained in the following: the book that he wrote On Life and Death, in which he determines about “Inhalation and Exhalation,” by which life is preserved in some living things, and about “Youth and Old Age,” by which the stages of life are differentiated; likewise the book entitled On Causes of Length and Shortness of Life, and the book that he wrote On Health and Disease, which also pertain to the disposition of life; and also the book he is said to have written On Nutrition and the Nourishing. We do not yet have these last two books.

Another part of the consideration pertains to the moving part of soul. This is contained in two books: the book On the Cause of Movement of Animals; and the book On the Progression of Animals, in which there is a determination about the parts of animals adapted for movement.

The third part of the consideration pertains to the sensitive part of soul, concerning which consideration can be made, first, of what pertains to the act of the internal or of the external sense power, and to this extent consideration of the sensitive part is contained in the present book, which is entitled On Sense and What Is Sensed, that is, On the Sensitive Part and the Sensible Object, in which is also contained the treatise On Memory and Recollection. (A possible source of confusion should be clarified. In the dominant traditional ordering of Aristotle’s works, De sensu et sensato, the sequel to De anima, is followed by De memoria et reminiscentia. Aquinas accepted this ordering and followed it in his commentaries on the three works. Toward the beginning of his commentary on De sensu et sensato, however, apparently under the influence of Averroes, he characterizes De memoria et reminiscentia as the second “treatise” of the “book,” De sensu et sensato, and Gauthier’s edition (i.e., the Leonine edition: tomus 45.2, ed. R.-A. Gauthier [Rome: Commissio Leonina; Paris: Librairie Philosophique J. Vrin, 1985]) accordingly presents a single commentary on two treatises of one book. But at the beginning of his commentary on De memoria et reminiscentia, Aquinas provides a commentator’s prologue, apparently signaling the beginning of a distinct commentary on a distinct work, and he now calls De memoria et reminiscentia a “book.” In keeping with Aquinas’s second thoughts, and with traditional Aristotelian and Thomistic scholarship, the present volume distinguishes two translations by two translators of two Thomistic commentaries on two Aristotelian works.) Again, what causes the difference between sensing and not-sensing that is brought about by sleep and wakefulness also pertains to consideration of the sensitive part, and this is determined in the book entitled On Sleep and Wakefulness.

6. But because one should pass through the more similar to the dissimilar, the order of these books seems reasonably to be such that after the book On the Soul, in which it is determined about soul in itself, there immediately follows the present book On Sense and What Is Sensed, because sensing itself pertains more to soul than to body. Next in order should be the book On Sleep and Wakefulness, which imply binding and freeing of the sense power. Then follow the books that pertain to the moving part, which is next closest to the sensitive part. And last in order are the books that pertain to the general consideration of a living thing, because this consideration to the greatest extent involves bodily disposition.

7. Accordingly, the present book, which is entitled On Sense and What Is Sensed, is first divided into two parts:

a prologue,

and the treatise, which begins where he says: about sense and sensing (436b8; [19]).

On the first point, he does two things.

First, he makes clear his intention, showing what is to be treated.

Second, he gives the reason why it is necessary to treat of such things, where he says: the greatest (436a6; [8]).

Accordingly, he first says that it was already determined about soul in its very self in the book On the Soul, (Aristotle, On the Soul 2.1; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 1, nn. 220–34.) that is, where he defined soul. Again, it was subsequently determined about each virtue—that is, power—of it, I mean from the point of view of it. (Aristotle, On the Soul 2.3ff; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 5, n. 279ff. “Virtue” translates the Latin virtus, which translated for Aquinas the Greek dunamis; “power” translates Aquinas’s term potentia. Aristotle’s On the Soul defines the soul in 2.1–2.2, then discusses the powers of soul in 2.3–3.12.) For since powers of soul, apart from intellect, are actualities of parts of a body, there can be consideration of them in two ways: in one way according as they pertain to soul as certain powers or “virtues” of it, and in another way from the point of view of body. Accordingly, it was determined about powers of soul themselves from the point of view of soul itself in the book On the Soul, but now the next thing is to make a consideration about animals, and everything that has life—which he adds because of plants—namely, by determining what are their proper operations—that is, proper to particular species of animals and plants—and what are common—that is, common to either all living things, or all animals, or many kinds of animals. Accordingly, let the things that were said about soul be underlying, or supposed—that is, let us use them in what follows as suppositions that have already been explained. And let us speak about the rest, and first about what is first—that is, first about what is common and after about what is proper: for that is the order required in natural science, as was determined at the beginning of the book, The Physics. (Aristotle, Physics 1.1, 184a23–24; cf. Aquinas, Commentary on Physics, bk. 1, lect. 1.)

8. Then, when he says: the greatest (436a6), he shows the necessity of this subsequent consideration.

If the proper as well as common operations of animals and plants were proper to soul itself, the consideration of soul would suffice for this purpose; but because they are common to soul and body, it is necessary, after the consideration of soul, to determine about them so that it may be known what kinds of bodily dispositions are required for these operations or affection. And so the Philosopher here shows that all of them are common to soul and body. On this point, he does three things.

First, he presents what he intends.

Second, he enumerates the features with which the intention is concerned, where he says: for instance, sense and memory (436a8; [9]).

Third, he proves the proposal, where he says: that all the abovementioned (436b1; [17]).

Accordingly, he says first that of the features that pertain to animals and plants, those that are greatest—that is, the outstanding ones—whether they are common to all animals or several, or proper to individual species, are seen, even at very first sight, to be common to soul and body. Hence they require another consideration beyond the one about soul taken absolutely.

9. Then, when he says: for instance, sense and memory (436a8), he enumerates the features with which the intention is concerned.

First, he presents what pertains to the sensitive part, namely sense and memory. He makes no mention of the other sense powers, namely imagination and the estimative power, because these are not distinguished from sense from the point of view of the thing known, since they are of present things, or of things taken as present. But memory is so distinguished by the fact that it is of past things inasmuch as they are past. (For more on the distinction of the “internal sense powers,” see ST I.78.4.)

10. Second, he presents what pertains to the locomotive part. Now the proximate principle of movement in animals is sensitive appetite, which is divided into two powers, namely irascible and concupiscible, as was said in On the Soul 3. (Aristotle, On the Soul 3.9, 432b6; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 3, lect. 8, nn. 802–6. Cf. ST I.81.2.)

Accordingly, he mentions anger, which pertains to the irascible power, and desire, which pertains to the concupiscible. It is from these two passions, as from what is more evident, that the two powers are named: for the concupiscible power is named from “desire” and the irascible power from “anger” (ira). (The term “concupiscible” is based on “concupiscence” (concupiscentia), which is the name of a kind of desire (desiderium): see ST I-II.25.2, obj. 1; ST I-II.30.1, ad 2. On the term “irascible,” see ST I-II.25.3, ad 1.) But because there are other passions of the soul pertaining to the appetitive power, he adds and appetite as a whole, to include everything that pertains to the appetitive power.

11. But all passions of the soul, whether they are in the irascible or the concupiscible power, are followed by pleasure and pain, as is said in Ethics 2. (Aristotle, Nicomachean Ethics 2.3, 1104b14–15; cf. Aquinas, Commentary on Ethics, bk. 2, lect. 3.) And so he adds, and with these, pleasure and pain, the final and ultimate passions, as it were.

He adds that these features that have been enumerated are almost all found in all kinds of animals. He says almost all because most of them, namely sense, desire, appetite, and pleasure and pain, are found in all animals, perfect as well as imperfect. For imperfect animals have, of the senses, only touch; they also have imagination, desire, and pleasure and pain, although these are indeterminate in them; and they are moved in an indeterminate way, as was said in On the Soul 3. (Aristotle, On the Soul 3.11, 433b31–434a5; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 2, lect. 30, n. 302; bk. 2, lect. 29, n. 644; bk. 3, lect. 10, nn. 838–39.) But memory and anger are not found in them at all, but only in perfect animals.

The reason for this is that not everything belonging to a lower genus, but only what is highest or more perfect, achieves a participation of likeness in what is proper to a higher genus. (The principle is Neoplatonic. See Pseudo-Dionysius, On the Divine Names 7.3; Pseudo-Dionysius, The Complete Works, trans. Colm Luibheid (New York-Mahwah: Paulist Press, 1987), p. 109.)

Now the sense power differs from intellect and reason because intellect or reason is of universals, which are everywhere and always, but the sense power is of individuals, which are here and now. And so sense, according to its proper nature (ratio) is apprehensive only of what is present.

12. But if there is a power of the sensitive part that extends to something not present, this is according to participation by likeness in reason or intellect. Hence memory, which is able to know things past, belongs only to perfect animals, being something supreme in sensitive knowledge.

Likewise, the sensitive appetite that follows from sense is, according to its proper nature (ratio) appetite for what is pleasant according to sense, and this appetite pertains to the concupiscible power that is common to all animals. But if an animal tends by appetite to something laborious, such as fighting or something similar, this contains a likeness to rational appetite, to which it is proper to desire some things for the sake of an end that are not in themselves desirable. And so anger, which is appetite for retribution, belongs only to perfect animals, because of an approach to the genus of what is rational.

13. Then he presents what pertains in any way to the nature of life (436a11).

He says that with the foregoing, other features are found in animals, some of which are common to everything that participates in life, that is, not only animals but also plants; but some pertain only to some kinds of animals. And the outstanding of these are listed in four pairs.

The first pair he presents is wakefulness and sleep, which are found in all animals, but not in plants.

The second is youth and old age, which are found in animals as well as plants, for the life of anything subject to death and birth is divided into different ages.

The third is inhalation and exhalation, which are found in certain kinds of animals, namely all that have lungs.

The fourth is life and death, which are found in all living things in this lower world.

And he says that about all of these it must be considered what each of them is, and what is its cause.

Because he said that the abovementioned features are the greatest, he adds something about some that are not so outstanding, namely health and disease, which are not both found in all individuals of the genera in which they exist by nature, as does happen with the abovementioned, but which are by nature found in all living things, animals as well as plants.

14. He says that it also pertains to the natural philosopher to discover first and universal principles of health and sickness. Consideration of particular principles pertains to the physician, the artisan who makes health, as it pertains to any operative art to consider particulars about its own business, because operations take place in particulars.

He proves in two ways that the former consideration does pertain to the natural philosopher, where he says: for it is impossible (436a18).

15. First, he does so by argument. Health or sickness can be found only in what has life, from which it is clear that the living body is the proper subject of health and disease. But the principles of a subject are also the principles of its proper attribute (passio). Hence, since it pertains to the natural philosopher to consider the living body and its principles, he must also consider the principles of health and disease.

16. Second, he proves the same thing by a sign or example that he concludes to from an argument that he presents. Most natural philosophers finish their study with what belongs to medicine, and likewise most physicians—that is, those who pursue the art of medicine more philosophically, not only applying experience, but inquiring into causes—begin their consideration of medicine with what is natural. From this it is clear that consideration of health and disease is common to both physicians and natural philosophers.

The reason for this is that health is sometimes caused by nature alone, and because of this it pertains to the consideration of the natural philosopher, to whom it belongs to consider the workings of nature; but sometimes it is caused by art, and in this respect it is considered by the physician. But because the art causes health not principally, but by as it were helping nature and ministering to it, the physician necessarily gets the principles of his science from the natural philosopher as from one who is prior, as a ship’s captain gets his principles from an astronomer. This is the reason why physicians who pursue their art well start with what belongs to natural philosophy.

But anything artificial that is made by art alone, for instance a house or a boat, in no way pertains to the natural philosopher’s consideration, just as what is made by nature alone in no way pertains to the consideration of art except inasmuch as art makes use of a natural thing.

17. Then, when he says: that all the abovementioned (436b1), he proves the proposal, namely that all the abovementioned are common to soul and body.

He uses the following argument. All the abovementioned pertain to the sense power. But the sense power is common to soul and body, for sensing pertains to the soul through the body. Therefore all the abovementioned are common to soul and body.

He makes the first premise clear by an induction, as it were. Of the abovementioned features, some take place together with the sense power, namely those that pertain to sensitive apprehension, such as sense, imagination, and memory. Some take place through the sense power, for instance those that pertain to the appetitive power, which is moved by the apprehension of sense power. Of the others, which pertain even more clearly to the body, some are affections of the sense power, namely sleep, which is a binding of sense power, and wakefulness, which is its freeing; some are conditions of the sense power, namely youth and old age, which have to do with whether the sense power is in good condition or is weak; some are protections of and benefits to the sense power, namely breathing, life, and health; and some are destructions and privations of it, namely death and sickness.

He says that the second premise, that sense is common to soul and body, is clear both by argument and without argument.

The argument is ready to hand. Since a sense power is affected by something sensible, as was shown in the book On the Soul, (Aristotle, On the Soul 1.5, 410a25–26; 2.5, 416b33–34; 2.11, 423b31–424a1; cf. Aquinas, Commentary on Aristotle’s On the Soul, bk. 1, lect. 12, n. 183; bk. 2, lect. 13, nn. 387–95; bk. 2, lect. 24, nn. 551–54.) and sensible things are bodily and material, what is affected by the sensible is necessarily bodily.

Even without argument this is clear from experience, because if the bodily organs are disturbed, the operation of the sense power is impeded; and if they are removed, the sense power is completely removed as well.