Physics   

in its own nature is not-being,-this not surviving as a constituent of
the result. Yet this causes surprise, and it is thought impossible
that something should come to be in the way described from what is
not.
In the same way we maintain that nothing comes to be from being, and
that being does not come to be except in a qualified sense. In that
way, however, it does, just as animal might come to be from animal,
and an animal of a certain kind from an animal of a certain kind.
Thus, suppose a dog to come to be from a horse. The dog would then, it
is true, come to be from animal (as well as from an animal of a
certain kind) but not as animal, for that is already there. But if
anything is to become an animal, not in a qualified sense, it will not
be from animal: and if being, not from being-nor from not-being
either, for it has been explained that by 'from not being' we mean
from not-being qua not-being.
Note further that we do not subvert the principle that everything
either is or is not.
This then is one way of solving the difficulty. Another consists in
pointing out that the same things can be explained in terms of
potentiality and actuality. But this has been done with greater
precision elsewhere. So, as we said, the difficulties which constrain
people to deny the existence of some of the things we mentioned are
now solved. For it was this reason which also caused some of the
earlier thinkers to turn so far aside from the road which leads to
coming to be and passing away and change generally. If they had come
in sight of this nature, all their ignorance would have been
dispelled.
Part 9
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