De Anima

But, as it is from the things which are naturally obscure, though more easily recognised by us, that we proceed to what is clear and, in the order of thought, more knowable, we must employ this method in trying to give a fresh account of soul. For it is not enough that the defining statement should set forth the fact, as most definitions do; it should also contain and present the cause: whereas in practice what is stated in the definition is usually no more than a conclusion. For example, what is quadrature? The construction of an equilateral rectangle equal in area to a given oblong. But such a definition expresses merely the conclusion. Whereas, if you say that quadrature is the discovery of a mean proportional, then you state the reason.

We take, then, as our starting-point for discussion that it is life which distinguishes the animate from the inanimate. But the term life is used in various senses; and, if life is present in but a

single one of these senses, we speak of a thing as living. Thus there is intellect, sensation, motion from place to place, the motion concerned with nutrition and, further, decay and growth. Hence it is that all plants are supposed to have life. For apparently they have within themselves a faculty and principle whereby they grow and decay in opposite directions. For plants do not grow upwards without growing downwards; they grow in both directions equally, in fact in all directions, as many as are constantly nourished and therefore continue to live, so long as they are capable of absorbing nutriment. This form of life can be separated from the others, though in mortal creatures the others cannot be separated from it. In the case of plants the fact is manifest: for they have no other faculty of soul at all.

It is, then, in virtue of this principle that all living things live, Sensation Wether animals or plants. But it is sensation primarily which constitutes the animal. For, provided they have sensation, even those creatures which are devoid of movement and do not change their place are called animals and are not merely said to be alive. Now the primary sense in all animals is touch. But, as the nutritive faculty may exist without touch or any form of sensation, so also touch may exist apart from the other senses. By nutritive faculty we mean the part of the soul in which even plants share. Animals, however, are found universally to have the sense of touch: why this is so in each of the two cases will be stated hereafter.

For the present it may suffice to say that the soul is the origin of the functions above enumerated and is determined by them, namely, by capacities of nutrition, sensation, thought, and by motion. But whether each one of these is a soul or part connection of a soul and, if a part, whether it is only logically functions. distinct or separable in space also is a question, the answer to which is in some cases not hard to see: other cases present difficulties. For, just as in the case of plants some of them are found to live when divided and separated from each other (which implies that the soul in each plant, though actually one, is potentially several souls), so, too, when insects or annelida are cut up, we see the same thing happen with other varieties of soul: I mean, each of the segments has sensation and moves from place

to place, and, if it has sensation, it has also imagination and appetency. For, where there is sensation, there is also pleasure and pain: and, where these are, desire also must of necessity be present. But as regards intellect and the speculative faculty the case is not yet clear. It would seem, however, to be a distinct species of soul, and it alone is capable of separation from the body, as that which is eternal from that which is perishable. The remaining parts of the soul are, as the foregoing consideration shows, not separable in the way that some allege them to be: at the same time it is clear that they are logically distinct. For the faculties of sensation and of opinion taken in the abstract are distinct, since to have sensation and to Opine are distinct. And so it is likewise with each of the other faculties above mentioned. Again, while some animals possess all these functions, others have only some of them, others only one. It is this which will differentiate animal from animal. The reason why this is so must be investigated hereafter. The case is similar with the several senses: some animals have all of them, others some of them, others again only one, the most indispensable, that is, touch.

Now"that by which we live and have sensation" is a phrase with two meanings, answering to the two meanings of "that by which we know" (the latter phrase means, firstly, knowledge and, secondly, soul, by either of which we say we know). Similarly that by which we have health means either health itself or a certain part, if not the whole, of the body. Now of these knowledge and health are the shape and in some sort form, the notion and virtual activity, of that which is capable of receiving in the one case knowledge, in the other health: that is to say, it is in that which is acted upon or conditioned that the activity of the causal agencies would seem to take effect. Now the soul is that whereby primarily we live, perceive, and have understanding: therefore it will be a species of

notion or form, not matter or substratum. Of the three meanings of substance mentioned above, form, matter and the whole made up of these two, matter is potentiality and form is actuality. And, since the whole made up of the two is endowed with soul, the body is not the actuality of soul, but soul the actuality of a particular body. Hence those are right who regard the soul as not independent of body and yet at the same time as not itself a species of body. It is not body, but something belonging to body, and therefore resides in body and, what is more, in such and such a body. Our predecessors were wrong in endeavouring to fit the soul into a body without further determination of the nature and qualities of that body: although we do not even find that of any two things taken at random the one will admit the other. And this result is what we might expect. For the actuality of each thing comes naturally to be developed in the potentiality of each thing: in other words, in the appropriate matter. From these considerations, then, it is manifest that soul is a certain actuality, a notion or form, of that which has the capacity to be endowed with soul.