On Generation and corruption
in' the water as in a vessel. This is impossible. For (i) there is
nothing to prevent an indeterminate number of matters being thus
'contained in' the water, so that they might come-to-be actually an
indeterminate quantity of air; and (ii) we do not in fact see air
coming-to-be out of water in this fashion, viz. withdrawing out of
it and leaving it unchanged.
It is therefore better to suppose that in all instances of
coming-to-be the matter is inseparable, being numerically identical
and one with the 'containing' body, though isolable from it by
definition. But the same reasons also forbid us to regard the
matter, out of which the body comes-to-be, as points or lines. The
matter is that of which points and lines are limits, and it is
something that can never exist without quality and without form.
Now it is no doubt true, as we have also established elsewhere,'
that one thing 'comes-tobe' (in the unqualified sense) out of
another thing: and further it is true that the efficient cause of
its coming-to-be is either (i) an actual thing (which is the same as
the effect either generically-or the efficient cause of the
coming-to-be of a hard thing is not a hard thing or specifically, as
e.g. fire is the efficient cause of the coming-to-be of fire or one
man of the birth of another), or (ii) an actuality. Nevertheless,
since there is also a matter out of which corporeal substance itself
comes-to-be (corporeal substance, however, already characterized as
such-and-such a determinate body, for there is no such thing as body
in general), this same matter is also the matter of magnitude and
quality-being separable from these matters by definition, but not
separable in place unless Qualities are, in their turn, separable.
It is evident, from the preceding development and discussion of
difficulties, that growth is not a change out of something which,
though potentially a magnitude, actually possesses no magnitude.
For, if it were, the 'void' would exist in separation; but we have
explained in a former work' that this is impossible. Moreover, a