2. To the Second Doubt

237. To the other doubt [n.232], against the other two conclusions [nn.201, 212], I say:

In one way, briefly one could, by evasion, say that a quality is a principle of action on a passive subject having the contrary quality, and this according to any degree it had before, and this as concerns the part of active quality. But, because of the subject in which the contrary determines for itself some degree more than another, it is possible that it [= the active quality] would not have power for every degree of the contrary (insofar as the contrary exists in such subject) in the same way in which it had power for it before. And this response will be made clear in what follows [nn.240, 247, 251-254, 257, 264265].

238. It could be said in another way that although the quality would have power for every degree of alteration that it had power for when conjoined [sc. when not separated from a substance], the consequence does not hold that it could have power for corruption of substance. - The idea of the first remark [‘although the quality would have...’] is as follows, that generation cannot be separated from corruption (relating it to a natural agent understood in this way) without whatever is created corrupting something simply, leaving behind something at the end of the corruption (for it does not annihilate things). Now a creature cannot corrupt something into a per se existing accident; therefore, if it corrupts, it corrupts into a substance, and consequently if it not have virtue for corrupting something into a substance, it does not corrupt at all; but a separated accident does not have virtue for corrupting into a substance.