Physics   

But not even movement in respect of place involves a void; for bodies
may simultaneously make room for one another, though there is no
interval separate and apart from the bodies that are in movement. And
this is plain even in the rotation of continuous things, as in that of
liquids.
And things can also be compressed not into a void but because they
squeeze out what is contained in them (as, for instance, when water is
compressed the air within it is squeezed out); and things can increase
in size not only by the entrance of something but also by qualitative
change; e.g. if water were to be transformed into air.
In general, both the argument about increase of size and that about
water poured on to the ashes get in their own way. For either not any
and every part of the body is increased, or bodies may be increased
otherwise than by the addition of body, or there may be two bodies in
the same place (in which case they are claiming to solve a quite
general difficulty, but are not proving the existence of void), or the
whole body must be void, if it is increased in every part and is
increased by means of void. The same argument applies to the ashes.
It is evident, then, that it is easy to refute the arguments by which
they prove the existence of the void.
Part 8
Let us explain again that there is no void existing separately, as
some maintain. If each of the simple bodies has a natural locomotion,
e.g. fire upward and earth downward and towards the middle of the
universe, it is clear that it cannot be the void that is the condition
of locomotion. What, then, will the void be the condition of? It is
thought to be the condition of movement in respect of place, and it is
not the condition of this.
Again, if void is a sort of place deprived of body, when there is a
void where will a body placed in it move to? It certainly cannot move
into the whole of the void. The same argument applies as against those
who think that place is something separate, into which things are
carried; viz. how will what is placed in it move, or rest? Much the
same argument will apply to the void as to the 'up' and 'down' in
place, as is natural enough since those who maintain the existence of
the void make it a place.
And in what way will things be present either in place-or in the void?
For the expected result does not take place when a body is placed as a
whole in a place conceived of as separate and permanent; for a part of
it, unless it be placed apart, will not be in a place but in the
whole. Further, if separate place does not exist, neither will void.
If people say that the void must exist, as being necessary if there is
to be movement, what rather turns out to be the case, if one the
matter, is the opposite, that not a single thing can be moved if there
is a void; for as with those who for a like reason say the earth is at
rest, so, too, in the void things must be at rest; for there is no
place to which things can move more or less than to another; since the
void in so far as it is void admits no difference.
The second reason is this: all movement is either compulsory or
according to nature, and if there is compulsory movement there must
also be natural (for compulsory movement is contrary to nature, and
movement contrary to nature is posterior to that according to nature,
so that if each of the natural bodies has not a natural movement, none
of the other movements can exist); but how can there be natural
movement if there is no difference throughout the void or the
infinite? For in so far as it is infinite, there will be no up or down
or middle, and in so far as it is a void, up differs no whit from
down; for as there is no difference in what is nothing, there is none
in the void (for the void seems to be a non-existent and a privation
of being), but natural locomotion seems to be differentiated, so that
the things that exist by nature must be differentiated. Either, then,
nothing has a natural locomotion, or else there is no void.
Further, in point of fact things that are thrown move though that
which gave them their impulse is not touching them, either by reason