Lecture 27 — Nothing eternal generated and corrupted, and conversely nothing generated and corruptible is eternal

191 But since the contradictory of 'that which is always capable of being' 'that which is not always capable of being'; while 'that which is always capable of not being' is the contrary, whose contradictory in turn is 'that which is not always capable of not being',

192 it is necessary that the contradictories of both terms should be predicable of one and the same thing, and thus that, intermediate between what always is and what always is not, there should be that to which being and not-being are both possible;

193 for the contradictory of each will at times be true of it unless it always exists. Hence that which not always is not will sometimes be and sometimes not be; and it is clear that this is true also of that which cannot always be but sometimes is and therefore sometimes is not. One thing, then, will have the power of being, and will thus be intermediate between the other two.

194 Expresed universally our argument is as follows. Let there be two attributes, A and B, not capable of being present in any one thing together, while either A or C and either B or D are capable of being present in everything. Then C and D must be predicated of everything of which neither A nor B is predicated. Let E lie between A and B; for that which is neither of two contraries is a mean between them. In E both C and D must be present, for either A or C is present everywhere and therefore in E. Since then A is impossible, C must be present, and the same argument holds of D.

195 Neither that which always is, therefore, nor that which always is not is either generated or destructible. And clearly whatever is generated or destructible is not eternal. If it were, it would be at once capable of always being and capable of not always being, but it has already been shown that this is impossible.

196 Surely then whatever is ungenerated and in being must be eternal, and whatever is indestructible and in being must equally be so. (I use the words 'ungenerated' and 'indestructible' in their proper sense, 'ungenerated' for that which now is and could not at any previous time have been truly said not to be; 'indestructible' for that which now is and cannot at any future time be truly said not to be.)

197 If, again, the two terms are coincident, if the ungenerated is indestructible, and the indestructible ungenearted, then each of them is coincident with 'eternal'; anything ungenerated is eternal and anything indestructible is eternal.

260. After showing that everything eternal is ungenerated and indestructible, the Philosopher here compares the eternal to the destructible and the generated, and shows that they cannot be at the same time.

First he prefaces certain things from which the argument proceeds;

secondly, from these he argues to his proposition, at neither that which always is (282a21; [264]).

Regarding the first he proposes three things.

First, indeed, he sets out the opposition between always to be and always not to be (282a4); and although he includes possible, he does not discuss the opposition according to "possible" and "not possible," but only that between "always being" and "not always being." He says therefore first that the contradictory denial of the affirmation possible always to be* is *possible not always to be: this negation is taken not on the part of "possible," in regard to which possible not always to be is affirmative, but on the part of not always to be. But possible always, not to be is opposed contrarily (according to the same mode) to what is possible always to be, the negative of which is possible not always not to be. The reason for this is that this adverb, always, designates universality of time, just as the sign, every, designates a universality of subjects. Hence, just as the contradictory of the statement, "Every man is," is "Not every man is," which is equivalent to "Some man is not," whereas the contrary of "Every man is," is "Every man is not," which is equivalent to "No man is," whose contradictory is "Not every man is not," which is equivalent to "Some man is"; so the contradictory of always to be is not always to be, which is equivalent to "not to be at some time"; whereas the contrary of "always to be" is always not to be, which is equivalent to "never to be," whose contradictory is not always, to be, which is equivalent to "sometime to be."

261. Secondly, at (282a7) he concludes from the aforesaid manner of opposition that the same subject must possess the negations of both, i.e., of "always to be" and "always not to be," which negations are not always to be and not always not to be. These negations are present in the same way in the same subject which is the medium between always being and always not being, which indeed can at one time be and at another time not be, as if we should say that between "every man is," and "no man is," the medium is "some man is" and "some man is not."

262. Thirdly, at to the effect that the negation of both, he proves that this conclusion follows from the foregoing.

First, by a proper argument based on the notion of the terms appearing in the question, to the effect that the negation of both, namely, both of that which is always to be and that which is always not to be, will at some time exist, i.e., posits something existing at some time, if it does not always exist, i.e., if by negation something is not posited always. For example, this negation not always to exist does not posit an eternal state either of being or of non-being; consequently, it posits to exist at some time, and at some time not to exist. And the same applies to the negation, not always not to exist. He concludes therefore that what is not always non-existent will at one time be and at another time not be, because thus is denied always not to exist without positing the thing in question always to exist. Likewise the negation, not always able to be, since it removes eternity of existence in such a way as not to posit eternity of non-existence, does posit "existence at some time." And because it does not posit eternal existence, there is nothing to prevent its not existing. Therefore "possible to be at some time" and "not to be some time" will be the same. And this is the medium between the two contraries, "always to be" and "always not to be."

263. Secondly, at expresed universally our argument (282a14) he proves the same thing with a common reason which, namely, applies to any terms. Let then A and B be two terms such that they can be found in no same thing, because they are contrary, in the case of always to be and always not to be. Take another term G, which is so related to A, that in every subject there must be either A or G—they being related as affirmation and negation, as, for example, always existing and not always existing. Then take another term D which is related to B in the same way as always not existing [B] is related to not always not existing [D]. It is necessary, therefore, that in everything which is neither A nor B, i.e., everything which neither always exists nor always does not exist, there inhere both G and D, which are the negations of both—since to that from which is removed always existing and always not existing, there is necessarily attributed not always existing (i.e., "at some time not to be"), and not always not existing (i.e., "to be some time"). Consequently, that subject from which both affirmations are removed and to which both negations are applied is a medium between A and B—for what denies both extremes is a medium between two contraries, as, for example, what is neither white nor black, is intermediate between white and black. In such a medium must necessarily exist both negations, namely, G and D. For, as was said, either G or A exists in everything whatsoever; consequently, one of them exists in E. Since, then, A cannot exist in E, it follows that G exists in E. And arguing on the same lines, D must exist in E. Thus, therefore, both G and D are predicates of E, from which both A and B are removed, since, namely, that at one time exists, and at another time does not, which neither always exists nor always does not exist. And this is what he intended to prove.

264. Then, at neither that which always is (282a21), from these premises he argues to his proposition. For if something always exists it is neither generated nor destructible; similarly, if something is always non-existent, it is neither generated nor destructible. Now it is manifest that also conversely, if something is generated or destructible, it is not eternal, either in respect to existing or in respect to non-existing. For if we assume the opposite as true, namely, that something is at once eternal and generated and destructible, it will follow that something is at once capable of always being and not always being, because the eternal can always exist but the generated and corruptible does not always exist. Now the impossibility of this was pointed out before: it was said that always to exist and not always to exist are opposed as contradictories. Hence what is left is that it is impossible for anything to be at once eternal and corruptible or generated.

265. Then, at surely then whatever is ungenerated (282a25), he shows that everything ungenerated and indestructible is eternal.

First he concludes this from the premises and says that it is necessary for everything ungenerated to be eternal, and likewise for everything indestructible to be eternal, provided it be being, and provided that ungenerated and indestructible are taken in their proper sense. The proper sense of "ungenerated" denotes something which now exists in such a way that it was not previously true to say that it did not exist; and "indestructible" denotes what now exists in such a way that it will not later be true to say of it that it does not exist. This is clear from what was said in distinguishing these words above.

266. Secondly, at if, again, the two terms (282a30), he proves the same point from what will be shown below. And he says that if ungenerated and indestructible are so related that everything ungenerated is indestructible and vice versa, then "eternal" must follow both, i.e., whatever is indestructible is eternal.

From all the foregoing the following argument can be formed: Nothing eternal is generated or destructible. Everything ungenerated and everything incorruptible is eternal. Therefore nothing ungenerated is destructible, and nothing indestructible has been generated.