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On The Soul   

a mean proportional between the two unequal sides of the given

rectangle discloses the ground of what is defined.

We resume our inquiry from a fresh starting-point by calling

attention to the fact that what has soul in it differs from what has

not, in that the former displays life. Now this word has more than one

sense, and provided any one alone of these is found in a thing we

say that thing is living. Living, that is, may mean thinking or

perception or local movement and rest, or movement in the sense of

nutrition, decay and growth. Hence we think of plants also as

living, for they are observed to possess in themselves an

originative power through which they increase or decrease in all

spatial directions; they grow up and down, and everything that grows

increases its bulk alike in both directions or indeed in all, and

continues to live so long as it can absorb nutriment.

This power of self-nutrition can be isolated from the other powers

mentioned, but not they from it-in mortal beings at least. The fact is

obvious in plants; for it is the only psychic power they possess.

This is the originative power the possession of which leads us to

speak of things as living at all, but it is the possession of

sensation that leads us for the first time to speak of living things

as animals; for even those beings which possess no power of local

movement but do possess the power of sensation we call animals and not

merely living things.

The primary form of sense is touch, which belongs to all animals.

just as the power of self-nutrition can be isolated from touch and

sensation generally, so touch can be isolated from all other forms

of sense. (By the power of self-nutrition we mean that departmental

power of the soul which is common to plants and animals: all animals

whatsoever are observed to have the sense of touch.) What the

explanation of these two facts is, we must discuss later. At present

we must confine ourselves to saying that soul is the source of these

phenomena and is characterized by them, viz. by the powers of

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