Lecture 2 — The definition of soul and body explained

It has been stated universally, then, what the soul is. For it is the substance that is according to account; and this is the what-it-was-to-be for a certain sort of body, just as if some tool, for example, an axe, were a natural body, for “being-an-axe” would be its substance, and this would be its soul. Apart from this, it would no longer be an axe, expect equivocally. But now it is an axe. For the soul is not the what-it-was-to-be and account of such a body as this, but of this sort of natural body, one that has within itself a principle of movement and rest.

Now, what has been said should be considered with respect to its parts. For if the eye were an animal, sight would in fact be its soul. For this is the eye’s substance according to account, whereas the eye is the matter of sight, and apart from this it is an eye no longer, save equivocally, as with a painted or stone eye. What, therefore, holds of a part, we ought to apply to the whole living body; for the relation of a part of the soul to a part of the body corresponds to that of sensitivity as a whole to the whole sensitive body, considered as such.

Now, that which has cast off its soul is not in potency to life, but rather, that which has life. But seed and fruit are only in potency such a body. As cutting or seeing is act, so is being awake, whereas the soul is like sight and the capacity of a tool; the body, however, is like the thing in potency. But as an eye is the pupil and sight, so the animal is the body and soul.

Therefore, it is not unclear that the soul is not separable from the body—or certain parts of it are inseparable, if it is naturally apt to be divided—for it is of certain bodily parts themselves that it is the act. But with respect to certain parts, there is nothing to prevent this, because these are not acts of any body. However, it is unclear whether the soul is the act of the body in the way that a sailor is of his ship. Let these remarks, then, serve to describe and determine the soul in outline.

235. It has been stated universally, then (412b9; [236]). The Philosopher now begins to make manifest the definition of the soul just given. And concerning this he does two things.

First, he makes the definition manifest.

Second, at therefore it is evident (413a4; [242]), he draws a conclusion from it as manifested.

As regards the first, he does two things:

in the first of which, he manifests the definition as regards what is placed in it on the side of the soul itself;

while in the second, where he says, now, that which has cast off (412b25; [240]), he manifests it as regards what is placed in it on the side of its subject.

Concerning the first, he does two things.

First, he manifests the definition of the soul based on a likeness with artificial things.

Second, at now, what has been said (412b17; [239]), he manifests it by considering its parts.

For artificial forms are accidents that are more known to us than are substantial forms, insofar as they are closer to sensation; this is why he fittingly manifests the account of the soul, which is a substantial form, through a comparison with accidental forms.

Likewise even the soul’s parts or powers are more manifest to us than is the soul itself (for all our inquiry into the soul has to start from objects to acts, and from the acts to the powers, through which the soul itself is made known to us); that is why the account of the soul becomes manifest also through its parts.

236. First, then, he observes that what the soul is has been given in the universal, since the definition above applies to any soul. (Lect. 1, n. 233.) For it posits the soul as the substance that is form, and from this a thing’s account is received. (Lect. 1, nn. 220–24.) However, there is this difference between a form that is substance and a form that is not substance; for an accidental form, which is not in the genus of substance, does not pertain to the essence or “whatness” of its subject (for whiteness is not of the essence of a white body), whereas substantial form is of the essence or “whatness” of its subject. The soul is said to be a substantial form, therefore, because it is of the essence or “whatness” of the ensouled body. Hence, he says, it is the substance (412b9) that is according to account, the what-it-was-to-be for a certain sort of body, that is, a body that is constituted in its species through this sort of form. For the form itself pertains to the essence of the thing, which is signified through a definition stating what a thing is.

237. And because substantial forms, including the forms of natural bodies, are hidden, Aristotle manifests this through artificial forms, which are accidental forms. So he adds, if some tool, that is, an artificial instrument, for example, an axe, were a natural body, that is, natural, it would possess a form in the manner explained. (Lect. 1, n. 218.) So he continues: then “being-an-axe” would be its substance, that is, would be the substantial form of the axe, which is that in reference to which the account of axe is given. This account he names the being of the axe, in that in reference to it an axe is said to be an axe; this form, he says, would be the substance of the axe. (He says this because the forms of natural bodies are in the genus of substance.)

And further, if the axe were not merely a natural body but an ensouled one as well, its form would be a soul; and if it lost this soul, it would no longer be an axe, except equivocally, just as when the soul is separated there is no longer an eye or flesh, except equivocally. But now, because the axe is not a natural body, nor is its form the “what it was to be” for such a body, if it lost the form of axe, it is an axe, that is, the substance of an axe, because the substance of artificial things is their matter, which remains when the artificial form is removed, even though the artificial body itself does not remain in act.

238. Then he explains why he has distinguished between the axe and as it would be if it were an ensouled natural body: for the soul is not the what-it-was-to-be and account, that is, the form, of such a body as this, that is, of an artificial body, but of this sort of natural body, that is, one that has life. To make manifest what a natural body is, he adds, one that has within itself a principle of movement and rest; for natural things are those that have within their very selves the principle of motion and rest; for nature is this sort of principle. (Aristotle, Physics 2.1, 192b13–14, 20–23; cf. Aquinas, Commentary on Physics, bk. 2, lect. 1.)

239. Then, at now, what has been said (412b17), he manifests the definition of the soul from its parts, saying that what was said about the soul as a whole and about the living body as a whole one should consider with respect to its parts. For if the eye were an animal, its soul would be sight, since sight is the substantial form of the eye and the eye is the matter of sight, in the same way as an organized body is the matter of a soul. But apart from sight the eye is no longer an eye, except equivocally, as with a painted or a stone eye, which is called an “eye” equivocally. (This is because equivocals are things whose name alone is common and the account of the substance is diverse.) Remove, then, the form from which arises the account of the eye’s substance; what remains is only the name “eye,” said equivocally.

And what is found in the part of a living body applies to the whole living body, namely, as sight is the substantial form of the eye, and when it is removed, the eye only remains equivocally, so too, the soul is the substantial form of the living body, and when the soul is removed, you have a living body only equivocally. For as one part of the sensitive soul is to one part of the sensitive body, so corresponds the sensitivity as a whole to the whole sensitive body, considered as such.

240. Next, at now, that which has cast off (412b25), he explains what was meant by defining the soul as the act of a body that has life in potency. For something is said to be “in potency” in two ways: in one way, as not having the principle of activity; in another way, as having this principle, but not acting according to it. However, the body whose act is the soul is one that has life in potency not in fact in the first sense but in the second.

So, when he says that a body is in potency to life, that is, a body whose act is the soul has life in potency, he is not speaking of a body that is in potency to life when it has cast off its soul, that is, one lacking the principle of life that is soul; he is speaking rather of that which has such a principle. On the other hand, a seed and fruit, in which the plant’s seed is preserved, is only potentially such a living body, which has a soul; for a seed does not yet have a soul but is in potency to soul. Therefore, it is in potency the way what has lost its soul is.

241. And to show just how the body whose act is the soul is in potency to life, he adds that being awake is the act of the sensitive soul in the same way as cutting is the act of a knife and seeing is the act of an eye; for each of these acts is the activity and use of a possessed principle. But the soul is the first act just as sight and any power of an organ; for each of these is the principle of the activity. But the body that has been completed by soul has first act in potency, but sometimes it lacks the second act. But as the eye is a thing composed of a pupil as its matter and sight as its form, so an animal is a thing composed of soul as its form and body as its matter.

242. Then, at therefore it is evident (413a4), he deduces a truth from the foregoing. Having shown that the soul is the whole body’s act, and its parts the acts of the body’s parts, and granted that acts and forms are not separated from that of which they are the acts or forms, it is manifest that the soul cannot be separated from the body—either the whole soul or certain parts of it, if the soul is naturally apt to have parts in some way. For obviously some parts of the soul are acts of certain parts of the body, as we have seen that sight is the eye’s act. (Lect. 1, n. 233.) On the other hand, as regards certain parts of the soul, there is nothing to prevent them from being separated, since certain parts of the soul are not the acts of any body, as will be proved when we come to treat of the intellect. (Bk. 3, lect. 1, nn. 671–99)

243. And because of Plato’s opinion that the soul is the act of the body not as its form but as its mover, he adds that it is not yet clear whether the soul is the act of the body as a sailor is that of a ship, that is, as its mover only.

244. Finally, he gathers together the things that have been said and says that the foregoing is an outline (413a9) description of the soul, meaning that it is extrinsic, as it were, and superficial and incomplete. For the determination will be completed when he reaches all the way to the determination of the innermost nature of each part of the soul.