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