2. Second Opinion

173. There is another opinion [Bonaventure, Albert the Great, Aquinas, Giles of Rome etc.], totally to the contrary, that it is impossible for anything to return numerically the same through a natural agent.

174. For this is adduced the authority of the Philosopher, On Generation 2.11.338b161-7, “Things whose substance has perished do not return the same in number.”

175. And there is his authority in Physics 5.4.228a6-12, about health, that it does not return numerically the same.

176. And his authority in Categories 10.13b20-27, “a return from privation to possession is impossible,” which is to be understood about the privation subsequent to form and about the preceding form. In agreement with this is what some allege from Metaphysics 8.5.1045a3-6, about wine and vinegar. And Aristotle denies that the return is immediate, even as to the species, because there must first be a resolution back into common matter.

177. There is also his authority in Ethics 6.3.1139b9-11 approving the saying of Solon [actually Agathon] that ‘God is deprived of this alone, to make undone what has been done;” therefore it is impossible to bring back past things, because this would then make them not only not to be past things but also to be present things.

178. Again, by four arguments:

The first is this: in every case of corruption, the matter of a generated thing is divided up, so that the generated thing is not generated from the whole same matter that was in the corrupted thing before, and thus further a greater and greater division of the matter is always being brought about. Therefore, in any circular process, if return is made to something of the same species as the thing first corrupted, it will not be from the same total matter, and consequently will not be the same, because identity of matter and of form is required for numerical identity- from the Philosopher Metaphysics 12.5.1071a17-29; and by reason, because identity of matter and form is the essential principle of the whole.

179. Again, a natural agent can only act through motion and change; but motion and change cannot return the same, because their unity is their continuity, and interruption or repetition is repugnant to continuity; repugnant therefore also to unity of motion and change. Therefore, the term of a natural agent cannot return the same.

This reason is confirmed as follows: as ‘this product’ is to product, so is ‘this production’ to production; therefore, by permutation, as product is to production, so is ‘this product’ to ‘this production’. But there cannot be product without production; therefore neither can there be ‘this product’ without ‘this production’. And ‘this production’ cannot return the same, because it is a change; therefore neither can ‘this product’ return the same.

180. Again, the same thing could not return unless there could be the same potency for it; but this is false, because either the same potency always remains or it is newly produced:

Not in the first way, because potency is corrupted in the arrival of form, and consequently, after the first reduction to act, the same potency does not remain. Nor in the second way, because just as a privation succeeds to the form different from the privation that preceded the form, so the form is resolved into a different potency - if it is resolved into any potency.

There is also a joint proof that neither way is possible, because there is no potency for the past; this form is past.

181. Why too is the same thing not brought back by nature immediately, if the potency for the same thing is in the receptive subject and if nature could be the active cause?

For since nature acts by impetus, there is no reason in this fact why nature may not as immediately bring back the same thing as not immediately do so when at least the sort of order of forms is in place by which it can bring back the same thing in species. But we clearly see that the same thing in number is not immediately brought back in the initial bringing back of the same thing in species - the fact is plain from the altogether different accidents that are consequent (at least as inseparable accidents) to the supposit itself.

And this question, posed by ‘why’, could be the fourth principal reason [n.178].