Lecture 29 — Refutation of corruptible ungenerated and incorruptible generated. Argument from natural science

205 To say then that there is no reason why anything should not be generated and yet indestructible or ungenerated and yet destroyed, to imagine that in the one case generation and in the other case destruction occurs once for all, is to destroy part of the data. For everything is capable of acting or being acted upon, of being or not being, either for an infinite, or for a definitely limited space of time; and the infinite time is only a possible alternative because it is after a fashion defined, as a length of time which cannot be exceeded. But infinity in one direction is neither infinite or finite.

206 Further, why, after always existing, was the thing destroyed, why, after an infinity of not being, was it generated, at one moment rather than another? If every moment is alike and the moments are infinite in number, it is clear that a generated or destructible thing existed for an infinite time. It has therefore for an infinite time the capacity of not being (since the capacity of being and the capacity of not being will be present together), if destructible, in the time before destruction, if generated, in the time after generation. If then we assume the two capacities to be actualized, opposites will be present together.

207 Further, this second capacity will be present like the first at every moment, so that the thing will have for an infinite time the capacity both of being and of not being; but this has been shown to be impossible.

208 Again, if the capacity is present prior to the activity, it will be present for all time, even while the thing was as yet ungenerated and non-existent, throughout the infinite time in which it was capable of being generated. At that time, then, when it was not, at that same time it had the capacity of being, both of being then and of being thereafter, and therefore for an infinity of time.

209 It is clear also on other grounds that it is impossible that the destructible should not at some time be destroyed. For otherwise it will always be at once destructible and in actuality indestructible, so that it will be at the same time capable of always existing and of not always existing. Thus the destructible is at some time actually destroyed. The generable, similarly, has been generated, for it is capable of having been generated and thus also of not always existing.

210 We may also see in the following way how impossible it is either for a thing which is generated to be thenceforward indestructible, or for a thing which is ungenerated and has always hitherto existed to be destroyed. Nothing that is by chance can be indestructible or ungenerated, since the products of chance and fortune are opposed to what is, or comes to be, always or usually, while anything which exists for a time infinite either absolutely or in one direction, is in existence either always or usually. That which is by chance, then, is by nature such as to exist at one time and not at another. But in things of that character the contradictory states proceed from one and the same capacity, the matter of the thing being the cause equally of its existence and of its non-existence. Hence contradictories would be present together in actuality.

211 Further, it cannot truly be said of a thing now that it exists last year, nor could it be said last year that it exists now. It is therefore impossible for what once did not exist later to be eternal. For in its later state it will possess the capacity of not existing, only not of not existing at a time when it exists—since then it exists in actuality—but of not existing last year or in the past. Now suppose it to be in actuality what it is capable of being. It will then be true to say now that it does not exist last year. But this is impossible. No capacity relates to being in the past, but always to being in the present or future. It is the same with the notion of an eternity of existence followed later by non-existence. In the later state the capacity will be present for that which is not there in actuality. Actualize, then, the capacity. It will be true to say now that this exists last year or in the past generally.

212 Considerations also not general like these but proper to the subject show it to be impossible that what was formerly eternal should later be destroyed or that what formerly was not should later be eternal. Whatever is destructible or generated is always alterable. Now alteration is due to contraries, and the things which compose the natural body are the very same that destroy it.

276. After showing that "generable" and "destructible" follow one upon the other and likewise "non-generated" and "indestructible," the Philosopher here refutes the contrary opinion, on the ground that from such a contrary opinion some of the assumed principles must be destroyed.

First, he shows how such a position destroys the supposition that every power is referred to a determinate time;

secondly, he shows that it destroys the supposition that the same thing cannot simultaneously be and not be, at further, why, after always (283a11; [279]).

277. He says therefore first (283a4) that since it has been demonstrated from certain presupposed principles that every generated thing is destructible, and every non-generated is indestructible, and vice versa, consequently, whoever declares there is nothing to prevent a thing that was made or generated from being indestructible, or something non-generated from being destroyed, in such a way, however, that one of these, namely, the generated, is generated but once, and the other, namely, the destructible, is destroyed but once, without their being alternately generated and destroyed, necessarily destroys thereby one or the other of the principles that were presupposed. For if a conclusion follows syllogistically from the premises, the conclusion which follows with necessity from the premises cannot be destroyed, unless one of the premises be destroyed.

Now he seems to state this against Plato, who posited that the world was made but is indestructible, and consequently posited that the disorder from which the world was generated was ungenerated but destructible—although some say that Plato did not understand this in the way his words sound, against which meaning Aristotle is here disputing. But so far as the exposition of this book is concerned it makes no difference whether Plato felt this way or that, provided it becomes clear how this position is being refuted by the arguments of Aristotle.

278. So he takes up again one of the given principles from the assumption of which he had argued to the proof of his proposition. And he says that all things having a certain power can do something or be acted upon, or be or not be, in accordance with their power, either for an infinite time, or for some time of definite quantity, i.e., for a period of time that is absolutely finite. And because he had previously mentioned the meaning of power only with respect to a determinate time, he adds that the reason why things having power can do or be something for an infinite time is that even infinite time is in a sense determinate, namely, by reason, in such a way that no diversity can be found in it—since the infinite is that of which there is not more, i.e., than which something greater cannot be taken. This is notwithstanding the fact that in Physics III Aristotle refutes this definition of the infinite, saying that it is rather a definition of the whole and of the perfect, whereas the infinite is imperfect and after the manner of a part. For there Aristotle is speaking of the infinite with respect to that of it is in act, to which addition can always be made; but here he is speaking of it with respect to all that is of it in potency, and to which nothing can be added. And such is also the condition of time, about which we are now speaking—since time is not all at once but successive. Now a time which is infinite in some respect, i.e., in a qualified sense, namely, with respect to its beginning or its end, is neither absolutely infinite, because there can be more of it, nor absolutely determinate, because it does not have some certain quantity. And therefore, according to the aforesaid supposition, it cannot be that something have the power of doing or being acted upon, or of being or not being, for a time that is finite at one end and infinite at the other. But whoever declares that something is non-generated but destructible, or generated and indestructible, is positing that something has the power to be or not be for a time that is in one respect infinite and in another respect finite. Therefore he is destroying the aforesaid supposed principle.

279. Then, at further, why, after always (283a11), he shows that the above-mentioned position destroys still another principle that was assumed, namely, that it is impossible for the same thing to be and not to be. About this he does two things:

first, he proves his proposition from the viewpoint of the potency existing in what is assumed to be generated or destroyed;

secondly, from the cause of the same, at we may also see (283a29; [284]).

About the first he does two things:

first he shows that to suppose the non-generated to be destroyed, or something generated to be indestructible, implies that something can at the same time be and not be;

secondly, he shows that the same impossibility follows from the supposition that something destructible exists which is not destroyed, at it is clear also on other grounds (283a24; [283]).

In regard to the first he presents three arguments.

With respect to the first of these he says: if we posit that something ungenerated first always existed and later was destroyed at a certain sign of time, i.e., at some certain instant, no reason can be assigned why it should be destroyed in that instant rather than in any other of the infinite previous instants. Likewise if for an infinite time something was not existing and then came to be at a certain instant, no reason can be assigned why it could be or come to be more in that instant than in any of the infinite preceding ones. If the preceding time were supposed finite, a reason could be assigned, because it could be said that the thing had the power to exist or not exist for such and such a time and no more. But due to the fact that the thing is described as having existed or not having existed for an infinite time, the above-reason ceases. And therefore it is necessary to posit that the ungenerated could have not existed in each of the instants of the preceding time, and similarly that the generated thing was able to exist in each of the instants of the preceding time. For if there is nothing more, i.e., no better reason why it was able to be or not to be in that instant rather than any of the preceding, since infinite signs, i.e., an infinitude of instants preceded, it is plain that during that infinite time something will be generable in the sense that it could have been generated at any instant of that infinite time. And similarly it must be said that in each instant of that time the thing assumed ungenerated and later destroyed was destructible. Consequently it is plain that the thing assumed as pre-existing for an infinite time also had the potency not to be in that whole infinite time. It will follow therefore that something will simultaneously, i.e., at one and the same time, have the power to be and not be, in such a way, however, that on the part of what is ungenerated and destructible the existence preceded the non-existence, whereas on the part of what is generated and indestructible, the existence is after the non-existence. Now there is nothing to prevent us from assuming what is possible. If, then, we assume with regard to the ungenerated that it did not exist during that time in which it existed and was able not to exist, it will follow that opposites co-exist, namely, that it existed and did not exist at the same time. Consequently, the aforesaid supposition destroys what had been presupposed, namely, that it is impossible for the same thing to be and not be at the same time.

280. But this reason does not seem compelling. For nothing prevents what is possible, absolutely speaking, from being impossible under certain conditions. For example, if we suppose that Socrates is at some time seated, it is possible, absolutely speaking, for him not to be seated at that time, although it is not compossible. In like manner, it can be said that what has been existing for an infinite time had the power not to exist during that time—but not, however, in the sense that its non-existence is compossible with what was posited, namely, that it could be simultaneously with its actual being.

Now it should be stated that nothing prevents what is incompossible to that which is contingent from being absolutely possible, yet what is incompossible to that which absolutely must be, is absolutely impossible. That which exists naturally through an infinite time exists necessarily — since it is necessary that each thing be to the extent that the nature of things provides for it, for nothing ceases to be except when it can no longer be, since all things long to be. Hence if something is presented as possible to be, then by that very fact it is necessary to posit it as compossible to that which must be. Therefore if we posit that what has always existed was able not to exist all during that time, it follows that it was able at once to be and not be.

281. Further, this second capacity (283a17). In like manner, a fourfold order is found in the consideration of speculative reason. First, because there is a process from the general to the less general. And this order corresponds to the first order which we have called the order of apprehension, for universals are considered according to an absolute form, but particulars by applying form to matter, as the Philosopher in On the Heavens says, that the word heaven signifies a form, and this heaven signifies a form in matter.

282. Again, if the capacity (283a20). The second order is that according to which one goes from the whole to the parts. And this corresponds to the order of intention, inasmuch as, namely, the whole is considered prior to the parts, not just any parts but parts which are according to matter and which are of the individual — as in the case of a semi-circle, in the definition of which "circle" is used (for it is "half a circle") and of an acute angle, in the definition of which "right angle" is used (for an acute angle is an angle "less than a right angle"). To be divided in that manner is incidental to a circle and to a right angle; hence, neither is a part of the species of a circle or right angle. For parts of this sort [i.e. parts of the species] are prior in consideration to the whole and are used in the definition of the whole, as are flesh and bones in the definition of man, as is said in Metaphysics VII. Consequently, since for the infinite time before it existed it had the power to exist for an infinite time in the future, there was no reason why it could exist in that instant and not before, since it is not in potency to exist in a determinate time. What is left, therefore, is that it could have existed even at some time before it existed; thus it had the power to exist in that time in which it was not existing, and so it follows, according to the premises, that it was able to be and not be at the same time. And the same argument applies to what is assumed to have always been and is at a certain time destroyed.

283. Then, at it is clear also on other grounds (283a24) he concludes according to the same reasoning that it is impossible for something to be destructible and not be destroyed at some time. For someone could object to the foregoing arguments and say that everything generated is destructible according to its nature, but it can happen that what is destructible may never be destroyed, because some cause is preserving its existence, as Plato assumed that the world is in itself generated and destructible, but will always remain, because God wills it. (Some say that Plato did not understand that the world is destructible, as though it had within itself the necessary cause of its destruction, but that he described it in that way because he wanted to point out that it depends for its existence on another, i.e., that the necessity of its existence is not in it of itself but from God. But whatever Plato may have understood makes no difference to the present undertaking, since Aristotle is objecting to his words.) Hence he says that it is plainly impossible for something destructible not to be at some time destroyed. Because if it will not be destroyed at some time, it has the power not to be destroyed and thus will be indestructible; and yet it is assumed to be a destructible thing existing for an infinite time. Consequently, it will be always, i.e., for an infinite time, simultaneously actually destructible and indestructible. But what is destroyed does not exist forever, whereas the indestructible does exist forever. Therefore there will be something capable at the same time of always existing and not always existing. But that is impossible, as is plain from what was said above, because what can always exist, necessarily exists always, and hence cannot be not always existing. Consequently, it is clear that everything destructible will be destroyed sometime.

Similarly, if something is of its very nature generable, it is necessary that it be made. This does not mean that everything that can be generated will be generated at some time, for there are many things possible that will never be generated. But it cannot be that something now existing have a nature that is generable, and not have been generated, but have pre-existed from eternity. For what is generable does not have the natural power of always existing but of being able to be after it was at some time made. That is why he does not say that if it is generable, it will be made, but has been made 284.

284. Then, at we may also see (283a29), he proves the same from the viewpoint of the cause of what is assumed ungenerated and indestructible.

First he presents his argument;

Secondly, he rejects an objection, at further, it cannot truly be said (283b6; [285]).

He says therefore first that, as will be said, we may also see in the following way that it is impossible either for a thing which is at some time generated to be thenceforward indestructible, or for a thing which is ungenerated and has always hitherto existed, to be destroyed. What is indestructible or ungenerated cannot exist by chance — since the product of chance or fortune neither exists nor comes to be as that which is always or usually. Meanwhile, anything which exists in infinite time, either absolutely finite or infinite in one direction, namely, before or after, is in existence either always, as is that which exists in infinite time absolutely, or for the most part, as is that which is in infinite time as to one part. Therefore it is necessary that such things which are either generated or corrupted after an infinite time, have from nature that they will at some time be and at some time not be. But in things which at one time naturally are and at another are not, the same power is directed to contradictories, namely, to being and not being, since this characteristic of at some time being, and at some time not being, is had from matter inasmuch as it is subject to privation or form. Thus the same thing follows as before, namely, that opposites could exist in the same thing at the same time. For in what has been generated a matter in potency to non-existence remains—and so, since it is indestructible, it will at the same time be able to be and able not to be. And the same holds for the ungenerated.

285. Then, at further, it cannot truly be said (283b6) he excludes a certain objection. For someone could say that that indestructible thing which is generated has the power of not existing, not indeed with respect to the future, but with respect to the past; similarly what is ungenerated but destructible possesses a potency to existence with respect to the past. But he excludes this by saying that it is not true to assert now that it is at the present time last year, or any of the things which were in past time; nor can it be said that what exists now existed in the past year—for things are distinguished in time in such a way that the order of time cannot be reversed so as to make the past the present or attribute present things to the past. From this it is plainly impossible for something which at one time did not exist, later to have existence forever, as we have already concluded from the preceding argument. For by reason of the matter from which it was made it has the potency not to exist even after it does exist: but it cannot be said that it has the potency not to exist now, because it is already existing in act and thus opposites would co-exist, as was concluded in the previous arguments. But it follows that it has the potency to non-existence in regard to the past year or past time. But this is impossible as the following argument shows: That for which a thing has the potency or power can be made actual. If, therefore, it is possible for something with respect to past time either to be or not be, we can posit that last year was not, i.e., that what existed last year was not existing then. But this is impossible, as was set down previously, for no potency looks to what was made in the past, but to what is in the present or what will be.

The force of this argument consists in the fact that, since a potency looks only to the present or future, then if something is said to have a potency with respect to the past, it follows that the past is converted and made present or future.

286. Then, at considerations also (283b17), he proves his main proposition with an argument proper to natural science. And he says that also with a natural argument, and not a universal one, i.e., one that is logical or metaphysical, as the preceding were, it can be considered that it is impossible for that which always existed to be later destroyed, or for that which previously did not exist to be afterwards eternal. And this he proves because all destructible and generable things are alterable. For generation and destruction are the termini of alteration, and alteration passes from contrary to contrary. Consequently, it is plain that by the very contraries from which things come to be when previously they did not exist, such things are later destroyed and reduced back to the same by corruption. Thus, for example, if something from being hot is made cold, it can again be made hot by what is hot. And so it is plain that what has been generated, can again be destroyed; and that what was destroyed, was at one time generated.

287. It should be noted that these arguments of Aristotle are directed against the position that posits a world produced by generation and indestructible either of its very nature or through the will of God. But according to the Catholic faith, we hold that it began to be, not through a process of generation as from nature, but by flowing from a first principle whose power was not bound to give it existence in infinite time but as it willed, after previous non-existence, in order to manifest the excellence of its power over the totality of being, namely, that the totality of being depends entirely on it and its power is not confined or determined to the production of some given being. Now the things produced by it so as to exist forever have the potency and power to exist forever, and in no way at some time not to exist. For as long as they did not exist, they had no such power; but when they now exist, they have no power with respect to non-existence in the past but to the existence which now prevails or will be—for potency does not look to the past, but to the present or future, as the Philosopher says. Thus it is clear that the preceding arguments in no way impugn the judgment of the Catholic faith. And with this the doctrine of the first book is brought to an end.