Lecture 14 — The unity of the soul

Since knowledge does belong to the soul, as does sensing and opining, as well as desiring and deliberating and all appetite; and moreover, as in animals there is local motion, and even growth, rest, and decrease, all from the soul; is each of these in the whole soul, and do we understand and sense and do and undergo every particular experience with the whole soul? Or does each require a different part? And is life itself in any one of these parts? Or in many? Or in all? Or is it from some quite distinct cause?

Some say the soul is divided into parts, understanding with one part and desiring with another.

If, then, the soul is apt by its nature to be divisible, what holds it together? Not the body, certainly; much rather the contrary seems to be true, that the soul holds the body together, for when it leaves, the body expires and falls to pieces. If there is some other thing that makes it one, this other is rather the soul. One would then have to ask, concerning this other, whether it be one or made of several parts. If it is one, why not call it too the soul straightaway? But if it is divisible, reason again demands what it is that holds this together? And so on to infinity.

A further query arises about the soul’s parts: what power has each in the body? If the whole soul holds together the whole body, it would also be fitting if each of the parts controlled some part of the body. But this looks like an impossibility. For it is difficult even to imagine what part the intellect would hold together, or how.

It is also held that plants live after being divided, as do certain divided animals also, as if they had a soul specifically one but not numerically. For each of these parts is endowed with sensation and moves locally for a certain time. If they are not long-lived, that is no objection: they have not the organs requisite for the preservation of their natures. Nevertheless, in each of the parts are to be found all the parts of the soul; and those separated parts are specifically the same as each other and as the whole; as each other, as if they were not separable; as the whole, as having an indivisible unity.

Moreover, it would also seem that the principle in plants is some sort of soul. For plants have only this in common with animals, and while this is independent of the sensitive principle, nothing has sensation without having this.

199. Since knowledge does belong to the soul (411a26). Having reviewed and criticized earlier opinions on the soul, the Philosopher proceeds now to some doubts. And first he does two things:

First, he puts some questions of his own.

Second, he begins to answer them, at some say (411b5; [204]).

But first we have to realize that the activities of the soul, namely, sensation, understanding, desire, local motion, and growth, can be considered in two distinct ways.

We can consider the mode of these activities; and from this point of view we can distinguish, underlying these activities, three powers of the soul: the vegetative, the sensitive, and the intellectual.

200. And these powers differ. For while the vegetative or nutritive power acts through active and passive qualities, such as heat and cold and the like, the sensitive power (or sensation) requires no such sensible qualities for sensing, though it does depend on corporeal organs. But the intellectual requires neither of these, since it understands neither by means of sensible qualities, nor through an organ, but is completed without any organ.

201. But if we consider these activities according to their different kinds, then we distinguish five powers with five corresponding activities: the nutritive, sensitive, locomotive, appetitive, and intellectual powers, whose actions are to take nourishment, to sense, to move, to desire, and to understand.

202. Therefore, having discussed and criticized earlier opinions on the soul as a whole, the Philosopher begins now an inquiry into the parts and the activities of those parts. And he proposes two questions.

The first question is whether activities of the soul, which are knowledge and sensing, which pertains to sense, opining, which pertains to understanding, desiring, which pertains to the concupiscible appetite, deliberating, which pertains to the rational, and all appetite (which is in several, since he includes the irascible appetite together with these two), together with local motion and rest, growth, and decrease—whether all these pertain to the whole soul in such a way that each one occurs in every part of the soul, so that with each part we understand, sense, move, desire, and assimilate food; or whether the truth is not rather that each activity has its own determinate part, that is to say, that with one part we understand, with another we sense, and so on.

203. The second question is this. Granted that each activity has its special part of the soul, is this true of the activity of simply being alive? Is this activity proper to any one of these parts? Or many? Or all? Or does it perhaps belong to some other part?

204. Then, at some say (411b5), he answers these questions in order.

First, he answers the first one;

second, he answers the second, at moreover, it would seem also that the principle (411b27; [209]).

As to the first one, he states and then rejects a view of certain philosophers;

second, he disproves it at if, then, the soul is apt (411b6; [206]).

For some say that the activities of the soul do not belong to the whole soul but to its parts; for they say the soul is divisible, and that it understands with one and desires with another, just as some people hold that the sensitive power is in the brain, the vital power in the heart, and so on.

205. Now, this is in a way true and in a way false. If you take it to mean that the soul has different potential parts, then it is quite true that it has diverse parts and powers, and that one understands by one part and senses by another. For the soul is a certain potential whole, and a potential part is taken there in respect to its whole capacity. But if you take it quantitatively, as though the soul were of a certain magnitude or quantity divided into diverse quantitative parts, then this opinion is false. And this was how the philosophers in question thought of the soul as divisible—even to the extent that they made out the soul’s different powers to be different souls.

206. Next, at if, then, the soul is apt (411b6), Aristotle disproves this last opinion with three arguments.

The first is this. Different things cannot come together except by something else that unites them. Therefore, if the one body contained several souls, these would have to be held together and unified by something. But there is nothing else that can hold them together and unite them; therefore they are not diverse.

That there is no other holding together and uniting the soul is clear as follows. Either it is the body that it is in or it is something else. But the body does not unite and hold it together; rather, the body is held together and unified by its soul; for we see that the body falls to pieces when the soul leaves it. If something else holds it together, then this will be soul most of all, since it pertains especially to the soul to hold together and to govern. And if this will be the soul, we must then ask whether this is itself one, or made of several parts. If of several parts, then what unites them? And so on to infinity. But if this is one, then why not call it the soul straightaway, that is, why not concede at the beginning that the soul is one? The soul, then, is not, as they thought, divisible into quantitative parts.

207. The second argument comes at a further query (411b14). If the different parts of the soul are in different parts of the body, then each soul-activity has a determinate part of the body or bodily organ. But this is impossible, since the intellect has no determinate part or organ in the body. Hence the soul does not have diverse parts, as they said.

208. The third argument starts at it is also held (411b19). If the various activities of soul are in diverse parts, then no one part is the organ of several distinct activities, nor are there several parts in an animal body the same in species. But we do find that certain ensouled things have parts with several activities each and have a soul that is identical in species in the whole and in all the parts; for example, in plants and in certain segmented animals that go on living after being cut up, the cut off parts still sense and move for a certain time. And if it is said that these parts live for only a short time, this does not matter, since they lack the organs requisite for preservation of their natures. The point is that several soul-activities exist in several distinct corporeal parts at once, and the latter are specifically similar to each other and to the whole. Therefore, the soul is not divided according to the different parts of the body.

However, the reason why such animals go on living after being divided is that to the degree that a soul is more perfect, so too does it exercise more and diverse activities, and therefore to exercise such activities many and diverse bodily organs are needed. And because the rational soul is nobler and more perfect, to that degree it requires a greater diversity of organs; but the soul that is in segmented animals or even in plants, because it has only a modicum of perfection and does not exercise diverse activities, needs a body that is more uniform, and it is preserved in each of its parts.

209. Then, at moreover, it would also seem (411b27), he answers the second question. Concerning this we must realize that life belongs, properly speaking, to things that move and act of themselves without being moved by others. So “to live” has two meanings. It can mean the existence of a living thing, and in this sense the Philosopher says that for living things, to live is to exist. (2.7, 415b13.) But it can also mean the activity of life.

210. Therefore one should say that the soul that is in plants, the vegetative soul, seems to be a certain principle that manifests life in lower realities; for nothing lives without it and all living things share in it, though in other ways their modes of life differ. For animals and plants have only vegetative activity in common.

Likewise, it can exist without sentient or intellectual activity, but the latter cannot exist without the vegetative; for no animal has sense or intellect without having vegetative life. Thus living is attributed to this principle (the vegetative) as sensing is attributed touch—not that animals live by the vegetative principle alone, but that it is the first principle in which life is manifested.