Physics   

in it nor yet greater than its extension, but equal to it; for the
extremities of things which touch are coincident.
Further, if one body is in continuity with another, it is not moved in
that but with that. On the other hand it is moved in that if it is
separate. It makes no difference whether what contains is moved or
not.
Again, when it is not separate it is described as a part in a whole,
as the pupil in the eye or the hand in the body: when it is separate,
as the water in the cask or the wine in the jar. For the hand is moved
with the body and the water in the cask.
It will now be plain from these considerations what place is. There
are just four things of which place must be one-the shape, or the
matter, or some sort of extension between the bounding surfaces of the
containing body, or this boundary itself if it contains no extension
over and above the bulk of the body which comes to be in it.
Three of these it obviously cannot be:
(1) The shape is supposed to be place because it surrounds, for the
extremities of what contains and of what is contained are coincident.
Both the shape and the place, it is true, are boundaries. But not of
the same thing: the form is the boundary of the thing, the place is
the boundary of the body which contains it.
(2) The extension between the extremities is thought to be something,
because what is contained and separate may often be changed while the
container remains the same (as water may be poured from a vessel)-the
assumption being that the extension is something over and above the
body displaced. But there is no such extension. One of the bodies
which change places and are naturally capable of being in contact with
the container falls in whichever it may chance to be.
If there were an extension which were such as to exist independently
and be permanent, there would be an infinity of places in the same
thing. For when the water and the air change places, all the portions
of the two together will play the same part in the whole which was
previously played by all the water in the vessel; at the same time the
place too will be undergoing change; so that there will be another
place which is the place of the place, and many places will be
coincident. There is not a different place of the part, in which it is
moved, when the whole vessel changes its place: it is always the same:
for it is in the (proximate) place where they are that the air and the
water (or the parts of the water) succeed each other, not in that
place in which they come to be, which is part of the place which is
the place of the whole world.
(3) The matter, too, might seem to be place, at least if we consider
it in what is at rest and is thus separate but in continuity. For just
as in change of quality there is something which was formerly black
and is now white, or formerly soft and now hard-this is just why we
say that the matter exists-so place, because it presents a similar
phenomenon, is thought to exist-only in the one case we say so because
what was air is now water, in the other because where air formerly was
there a is now water. But the matter, as we said before, is neither
separable from the thing nor contains it, whereas place has both
characteristics.
Well, then, if place is none of the three-neither the form nor the
matter nor an extension which is always there, different from, and
over and above, the extension of the thing which is displaced-place
necessarily is the one of the four which is left, namely, the boundary
of the containing body at which it is in contact with the contained
body. (By the contained body is meant what can be moved by way of
locomotion.)
Place is thought to be something important and hard to grasp, both
because the matter and the shape present themselves along with it, and
because the displacement of the body that is moved takes place in a
stationary container, for it seems possible that there should be an
interval which is other than the bodies which are moved. The air, too,
which is thought to be incorporeal, contributes something to the