,
for instance, only exists by virtue of its properties, yellowness,
heaviness, etc., and these qualities are just what it has in common
with other things. So that the particular, as such, has no existence,
but this is only the same as saying, what we have already said, that
matter has no existence apart from form.

A very natural mistake would be to suppose that by matter Aristotle
meant the same as we do, namely, physical substance, such as wood or
iron, and that by form he meant simply shape. Now although there is a
kinship in the ideas, these two pairs of ideas are far from identical.
Let us begin with matter. Our ordinary idea of matter as physical
substance is an absolute conception. That is to say, a thing which we
call material is absolutely, once and for all, matter. It is not
material from one point of view, and immaterial from another. In every
possible relation it is, and {277} remains, matter. Nor does it in
process of time cease to be matter. Brass never becomes anything but
matter. No doubt there are in nature changes of one sort of matter
into another, for example, radium into helium. And for all we know,
brass may become lead. But even so, it does not cease to be matter.
But Aristotle's conception of matter is a relative conception. Matter
and form are fluid. They flow into one another. The same thing, from
one point of view, is matter, from another, form. In all change,
matter is that which becomes, that upon which the change is wrought.
That is form towards which the change operates. What becomes is
matter. What it becomes is form. Thus wood is matter if considered in
relation to the bed. For it is what becomes the bed. But wood is form
if considered in relation to the growing plant. For it is what the
plant becomes. The oak is the form of the acorn, but it is the matter
of the oak furniture.

That matter and form are relative terms shows, too, that the form
cannot be merely the shape. For what is form in one aspect is matter
in another. But shape is never anything but shape. No doubt the shape
is part of the form, for the form in fact includes all the qualities
of the thing. But the shape is quite an unimportant part of the form.
For form includes organization, the relation of part to part, and the
subordination of all parts to the whole. The form is the sum of the
internal and external relations, the ideal framework, so to speak,
into which the thing is moulded. Form also includes function. For it