Physics   

'many a little makes a mickle': thus if many equal bodies can be
together, so also can many unequal bodies.
Melissus, indeed, infers from these considerations that the All is
immovable; for if it were moved there must, he says, be void, but void
is not among the things that exist.
This argument, then, is one way in which they show that there is a
void.
(2) They reason from the fact that some things are observed to
contract and be compressed, as people say that a cask will hold the
wine which formerly filled it, along with the skins into which the
wine has been decanted, which implies that the compressed body
contracts into the voids present in it.
Again (3) increase, too, is thought to take always by means of void,
for nutriment is body, and it is impossible for two bodies to be
together. A proof of this they find also in what happens to ashes,
which absorb as much water as the empty vessel.
The Pythagoreans, too, (4) held that void exists and that it enters
the heaven itself, which as it were inhales it, from the infinite air.
Further it is the void which distinguishes the natures of things, as
if it were like what separates and distinguishes the terms of a
series. This holds primarily in the numbers, for the void
distinguishes their nature.
These, then, and so many, are the main grounds on which people have
argued for and against the existence of the void.
Part 7
As a step towards settling which view is true, we must determine the
meaning of the name.
The void is thought to be place with nothing in it. The reason for
this is that people take what exists to be body, and hold that while
every body is in place, void is place in which there is no body, so
that where there is no body, there must be void.
Every body, again, they suppose to be tangible; and of this nature is
whatever has weight or lightness.
Hence, by a syllogism, what has nothing heavy or light in it, is void.
This result, then, as I have said, is reached by syllogism. It would
be absurd to suppose that the point is void; for the void must be
place which has in it an interval in tangible body.
But at all events we observe then that in one way the void is
described as what is not full of body perceptible to touch; and what
has heaviness and lightness is perceptible to touch. So we would raise
the question: what would they say of an interval that has colour or
sound-is it void or not? Clearly they would reply that if it could
receive what is tangible it was void, and if not, not.
In another way void is that in which there is no 'this' or corporeal
substance. So some say that the void is the matter of the body (they
identify the place, too, with this), and in this they speak
incorrectly; for the matter is not separable from the things, but they
are inquiring about the void as about something separable.
Since we have determined the nature of place, and void must, if it
exists, be place deprived of body, and we have stated both in what
sense place exists and in what sense it does not, it is plain that on
this showing void does not exist, either unseparated or separated; the
void is meant to be, not body but rather an interval in body. This is
why the void is thought to be something, viz. because place is, and
for the same reasons. For the fact of motion in respect of place comes
to the aid both of those who maintain that place is something over and
above the bodies that come to occupy it, and of those who maintain
that the void is something. They state that the void is the condition
of movement in the sense of that in which movement takes place; and
this would be the kind of thing that some say place is.
But there is no necessity for there being a void if there is movement.
It is not in the least needed as a condition of movement in general,
for a reason which, incidentally, escaped Melissus; viz. that the full
can suffer qualitative change.