On Generation and corruption
exhibit them, why they do so, and in what manner. We must go on to
discuss how it is possible for action and passion to take place.
Some philosophers think that the 'last' agent-the 'agent' in the
strictest sense-enters in through certain pores, and so the patient
suffers action. It is in this way, they assert, that we see and hear
and exercise all our other senses. Moreover, according to them, things
are seen through air and water and other transparent bodies, because
such bodies possess pores, invisible indeed owing to their minuteness,
but close-set and arranged in rows: and the more transparent the body,
the more frequent and serial they suppose its pores to be. Such was
the theory which some philosophers (induding Empedocles) advanced in
regard to the structure of certain bodies. They do not restrict it
to the bodies which act and suffer action: but 'combination' too, they
say, takes place 'only between bodies whose pores are in reciprocal
symmetry'. The most systematic and consistent theory, however, and one
that applied to all bodies, was advanced by Leucippus and
Democritus: and, in maintaining it, they took as their
starting-point what naturally comes first.
For some of the older philosophers thought that 'what is' must of
necessity be 'one' and immovable. The void, they argue, 'is not':
but unless there is a void with a separate being of its own, 'what is'
cannot be moved-nor again can it be 'many', since there is nothing
to keep things apart. And in this respect, they insist, the view
that the universe is not 'continuous' but 'discretes-in-contact' is no
better than the view that there are 'many' (and not 'one') and a void.
For (suppose that the universe is discretes-in-contact. Then), if it
is divisible through and through, there is no 'one', and therefore
no 'many' either, but the Whole is void; while to maintain that it
is divisible at some points, but not at others, looks like an