ON YOUTH AND OLD AGE, ON LIFE AND DEATH,
translated by G. R. T. Ross
WE must now treat of youth and old age and life and death. We must
probably also at the same time state the causes of respiration as
well, since in some cases living and the reverse depend on this.
We have elsewhere given a precise account of the soul, and while
it is clear that its essential reality cannot be corporeal, yet
manifestly it must exist in some bodily part which must be one of
those possessing control over the members. Let us for the present
set aside the other divisions or faculties of the soul (whichever of
the two be the correct name). But as to being what is called an animal
and a living thing, we find that in all beings endowed with both
characteristics (viz. being an animal and being alive) there must be a
single identical part in virtue of which they live and are called
animals; for an animal qua animal cannot avoid being alive. But a
thing need not, though alive, be animal, for plants live without
having sensation, and it is by sensation that we distinguish animal
from what is not animal.
This organ, then, must be numerically one and the same and yet
possess multiple and disparate aspects, for being animal and living
are not identical. Since then the organs of special sensation have one
common organ in which the senses when functioning must meet, and
this must be situated midway between what is called before and
behind (we call 'before' the direction from which sensation comes,
'behind' the opposite), further, since in all living things the body
is divided into upper and lower (they all have upper and lower
parts, so that this is true of plants as well), clearly the
nutritive principle must be situated midway between these regions.
That part where food enters we call upper, considering it by itself
and not relatively to the surrounding universe, while downward is that
part by which the primary excrement is discharged.
Plants are the reverse of animals in this respect. To man in