Lecture 12 — Actualizations of sense and intellect compared

The first change in the sensitive being is caused by the parent. When it is generated, it is already endowed with sense, like knowledge. But actual sensation is said to be like thinking itself.

They differ, however, because what actuates sense-activities—namely, the visible, the audible, and so on—is from outside. The cause of this difference is that actual sensation is of particulars, but scientific knowledge is of universals, which are, in a way, within the soul itself; hence, the act of the intellect is interior and at will, whereas sensation is not from within the soul, and requires that a sense-object be presented. The same holds good of the sciences which concern sense-objects and for the same reason, i.e., that sense-objects belong to singular and external things. But there will be time later to deal with these more conclusively.

For the present, it is sufficiently established that “in potency” is not spoken of in a simple way, but it means one thing when, for example, we say that a child is able to be a soldier, and quite another thing when we say this of an adult. The same holds of the sensitive power. Since, however, this distinction has no name, and yet it is settled that the two differ, and in what way, it is necessary to use the expressions “to be acted upon” and “to be altered” as if they were precise terms. The sensitive power is potentially that which the sense-object is actually, as we have said. It is acted upon insofar as it is not like; it becomes like in being acted upon, and it is then such as is the other.

373. The first change in the sensitive being (417b16). After distinguishing between potency and act and elucidating in terms of intellectual activity the movement from one state to the other, the Philosopher now applies what he has said to sensation. And about this he does three things.

First, he shows how something is brought forth from potency to act in sensing.

Second, at they differ, however (417b19; [375]), he explains the difference between sense and intellect.

Third, at for the present, it is sufficiently established (417b29; [381]), he recapitulates what has been said about sensation.

Regarding the first point, we must take into account that, as in knowledge, so too in sensation, there are two kinds of potency and of act.

For what so far possesses no sense power but is naturally apt to have one is in potency to the sense power; and what already has the sense power, but does not yet sense, is in potency to sensing, in the same way as we have seen in the case of knowledge. (Lect. 11, n. 359.)

Now, as a subject moves from first potency into first actuality when it acquires knowledge through teaching, so too, a subject’s first potency to the possession of a sense power is actualized by his generation.

For the sense power is naturally present in every animal, so that just as in its generation it acquires its own proper nature and species, so too, it acquires its senses. But the case is not the same with intellectual knowledge; it is not present in man by nature, but it is acquired through application and learning.

374. This is what he means by saying that the first change in the sensitive being is caused by the parent (417b16). This first change, he explains, is from pure potency to the first actuality, and it is due to the parent because there is a power in the seed to actualize the sensitive soul with all its capacities. When an animal has been generated, it is already endowed with its senses in the same way as a man who has been taught possesses knowledge. And actual sensation corresponds to the man who actually exercises his knowledge by thinking.

375. Then, at they differ, however (417b19), he sets himself to discriminate between actual sensation and thinking; and he finds the first reason for distinguishing these activities in the difference between their objects, that is, the sense-objects and intelligible objects, the things that are actually sensed and considered. For the sense-object, which actuates sense-activities—namely, the visible, the audible, and so on—is from outside the soul. The cause of this difference is that actual sensation is of particulars, which exist outside the soul; but scientific knowledge is of universals, which are, in a way, within the soul itself.

Whence it is clear that one who already has scientific knowledge does not need to seek his objects outside himself; he already possesses them inwardly, and hence, he is able, unless prevented accidentally, to think about them at will, whenever he wishes to do so. But sensation is not possible for someone whenever he wishes, because he does not have the sense-objects within himself, but rather they must be present outside him.

376. And as with sense-activities, so with the sciences which concern sense-objects; for the sense-objects are of the number of singulars and things external to the soul. Therefore, a man cannot speculate scientifically on any sense-objects that he wishes, but only on such as he perceives by sensation. But there will be time to treat conclusively of these matters later on, in book 3, where we discuss the intellect and its relation to the senses. (3.1–5, 429a10–431a4; 3.6, 431a4–b19; cf. lect. 28, nn. 622–36; bk. 3, lect. 1, lect. 6, nn. 765–778.)

377. Concerning what is said here, we have to ask ourselves:

why sensation is of individual things, whereas science is of universals;

and how exactly universals exist in the soul.

As to the first, we should note that sensation is a power in a bodily organ, whereas intellect is an immaterial power—it is not the actuality of any bodily organ. Now, everything received is received in the mode of the receiver, and not through its own mode. But all knowledge occurs through the thing known being somehow present in the knower (that is, present according to its likeness); for the knower in act is the thing known in act. Therefore the sense power receives in a bodily way the likeness of the reality being sensed, whereas the intellect receives in an incorporeal and immaterial way the likeness of the thing understood. Now, in material and corporeal realities, the common nature derives its individuation from matter contained under determinate dimensions, whereas the universal exists through an abstraction from such matter and the individuating material conditions. Clearly, then, a thing’s likeness as received in sensation represents the reality insofar as it is an individual; as received, however, in the intellect, it represents the reality according to the account of the universal nature. That is why individuals are known by the senses, and universals (of which are the sciences) by the intellect.

378. As to the second, note that the term “universal” can be taken in two senses. It can refer to the common nature itself insofar as it underlies the intention of universality; or it can refer to the universal taken in itself. As, for example, in a white thing, we can consider either the thing that happens to be white or the thing itself precisely as existing under whiteness.

Now, a nature—say, human nature—to which the intention of universality accrues has two modes of existence: one, material, insofar as it exists in its natural matter; the other, immaterial, insofar as it exists in the intellect. Therefore, insofar as it exists in its natural matter, the intention of universality cannot come to it, for it is individuated by matter; therefore, the intention of universality comes to it insofar as it is abstracted from individual matter. But it cannot exist in a real way as abstracted from individual matter, as the Platonists thought; for man exists only in this flesh and these bones, as the Philosopher proves in Metaphysics 7. (Aristotle, Metaphysics 7.8, 1034a5–8; 7.16, 1040b27–1041a5; cf. Aquinas, Commentary on Metaphysics, bk. 7, lect. 16, nn. 1642–47.) Therefore, it is only in the intellect that human nature has any being apart from the principles which individuate it.

379. Nevertheless, the intellect is not false when it apprehends a common nature apart from its individuating principles, without which it cannot exist in the nature of things; for the intellect does not apprehend that the common nature exists without the individuating principles, whereas it does apprehend the common nature without apprehending the individuating principles, and in this there is no falsehood. The alternative would indeed be false—just as, were I to separate whiteness from a white man such that I would understand him not to be white, this too would be a false apprehension; but if I were to separate the whiteness from the man such that I were apprehending man while apprehending nothing about his whiteness, that would not be a false apprehension. For the truth of an apprehension does not require that in merely apprehending some reality, we apprehend everything in it. Hence in this way the intellect abstracts, without any falsehood, a genus from the species insofar as it understands the nature of the genus without understanding the differences; or it may abstract the species from individuals insofar as it understands the nature of the species without understanding individuating principles.

380. It is clear, then, that the intention of universality can be attributed to a common nature only according to the existence that it has in the intellect. For a unity to be predicable of many things, it must first be conceived apart from the principles by which it is divided into many things. Whence, one concludes that universals as universal exist only in the soul, but the natures themselves, to which accrue the intention of universality, exist in the realities. That is why the common names that signify these very natures are predicated of individuals but the names that signify the intentions do not. For Socrates is a man, but he is not a species—even though man is a species.

381. Finally, at for the present (417b29), he recapitulates his remarks on sensation and observes that for the present, it is sufficiently established that what we say is in potency is not spoken of in a simple way. It is in one sense that we say that a child is able to be a soldier, that is, by a remote potency. But in another sense, we say that an adult can be a soldier, that is, by a proximate potency. And the same distinction applies to sense-perception, as we have seen there are two ways of being in potency to sensing anything. Though we have found no proper names to express this distinction of these potencies, it is settled, nevertheless, that the two potencies differ, and in what way they differ.

382. And in spite of the fact that something is not properly speaking said “to be altered” and “to be acted upon” inasmuch as it passes from the second potency into act, that is, insofar as what has the sense comes to be actually sensing, yet it is necessary to use the expressions “to be acted upon” and “to be altered” as if they were proper and fitting names; and this is because the sensitive power is potentially that which the sense-object is actually. It follows that, while at the beginning of being acted upon, the sense is not like its object, in being acted upon it now becomes like the sensible object and it is such as the other is. It was because they failed to make this distinction that the earlier philosophers thought that sense powers were composed of the sensible objects.