For some are called so by analogy,
as in geometry we say one thing is or is not a 'power' of another by
virtue of the presence or absence of some relation between them. But
all potencies that conform to the same type are originative sources of
some kind, and are called potencies in reference to one primary kind
of potency, which is an originative source of change in another
thing or in the thing itself qua other. For one kind is a potency of
being acted on, i.e. the originative source, in the very thing acted
on, of its being passively changed by another thing or by itself qua
other; and another kind is a state of insusceptibility to change for
the worse and to destruction by another thing or by the thing itself
qua other by virtue of an originative source of change. In all these
definitions is implied the formula if potency in the primary
sense.-And again these so-called potencies are potencies either of
merely acting or being acted on, or of acting or being acted on
well, so that even in the formulae of the latter the formulae of the
prior kinds of potency are somehow implied.
Obviously, then, in a sense the potency of acting and of being
acted on is one (for a thing may be 'capable' either because it can
itself be acted on or because something else can be acted on by it),
but in a sense the potencies are different. For the one is in the
thing acted on; it is because it contains a certain originative
source, and because even the matter is an originative source, that the
thing acted on is acted on, and one thing by one, another by
another; for that which is oily can be burnt, and that which yields in
a particular way can be crushed; and similarly in all other cases.
Pages:
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229