On The Soul   

essence of the whole living body.

That it is the last, is clear; for in everything the essence is

identical with the ground of its being, and here, in the case of

living things, their being is to live, and of their being and their

living the soul in them is the cause or source. Further, the actuality

of whatever is potential is identical with its formulable essence.

It is manifest that the soul is also the final cause of its body.

For Nature, like mind, always does whatever it does for the sake of

something, which something is its end. To that something corresponds

in the case of animals the soul and in this it follows the order of

nature; all natural bodies are organs of the soul. This is true of

those that enter into the constitution of plants as well as of those

which enter into that of animals. This shows that that the sake of

which they are is soul. We must here recall the two senses of 'that

for the sake of which', viz. (a) the end to achieve which, and (b) the

being in whose interest, anything is or is done.

We must maintain, further, that the soul is also the cause of the

living body as the original source of local movement. The power of

locomotion is not found, however, in all living things. But change

of quality and change of quantity are also due to the soul.

Sensation is held to be a qualitative alteration, and nothing except

what has soul in it is capable of sensation. The same holds of the

quantitative changes which constitute growth and decay; nothing

grows or decays naturally except what feeds itself, and nothing

feeds itself except what has a share of soul in it.

Empedocles is wrong in adding that growth in plants is to be

explained, the downward rooting by the natural tendency of earth to

travel downwards, and the upward branching by the similar natural

tendency of fire to travel upwards. For he misinterprets up and

down; up and down are not for all things what they are for the whole

Cosmos: if we are to distinguish and identify organs according to

their functions, the roots of plants are analogous to the head in