Others, indeed, have apprehended the nature in question, but not
adequately.

    In the first place they allow that a thing may come to be without
qualification from not being, accepting on this point the statement of
Parmenides. Secondly, they think that if the substratum is one
numerically, it must have also only a single potentiality-which is a
very different thing.

    Now we distinguish matter and privation, and hold that one of these,
namely the matter, is not-being only in virtue of an attribute which
it has, while the privation in its own nature is not-being; and that
the matter is nearly, in a sense is, substance, while the privation in
no sense is. They, on the other hand, identify their Great and Small
alike with not being, and that whether they are taken together as
one or separately. Their triad is therefore of quite a different
kind from ours. For they got so far as to see that there must be
some underlying nature, but they make it one-for even if one
philosopher makes a dyad of it, which he calls Great and Small, the
effect is the same, for he overlooked the other nature. For the one
which persists is a joint cause, with the form, of what comes to
be-a mother, as it were. But the negative part of the contrariety
may often seem, if you concentrate your attention on it as an evil
agent, not to exist at all.

    For admitting with them that there is something divine, good, and
desirable, we hold that there are two other principles, the one
contrary to it, the other such as of its own nature to desire and
yearn for it. But the consequence of their view is that the contrary
desires its wtextinction. Yet the form cannot desire itself, for it is
not defective; nor can the contrary desire it, for contraries are
mutually destructive. The truth is that what desires the form is
matter, as the female desires the male and the ugly the beautiful-only
the ugly or the female not per se but per accidens.

    The matter comes to be and ceases to be in one sense, while in
another it does not. As that which contains the privation, it ceases
to be in its own nature, for what ceases to be-the privation-is
contained within it. But as potentiality it does not cease to be in
its own nature, but is necessarily outside the sphere of becoming
and ceasing to be. For if it came to be, something must have existed
as a primary substratum from which it should come and which should
persist in it; but this is its own special nature, so that it will
be before coming to be. (For my definition of matter is just
this-the primary substratum of each thing, from which it comes to be
without qualification, and which persists in the result.) And if it
ceases to be it will pass into that at the last, so it will have
ceased to be before ceasing to be.

    The accurate determination of the first principle in respect of
form, whether it is one or many and what it is or what they are, is
the province of the primary type of science; so these questions may
stand over till then. But of the natural, i.e. perishable, forms we
shall speak in the expositions which follow.

    The above, then, may be taken as sufficient to establish that
there are principles and what they are and how many there are. Now let
us make a fresh start and proceed.