Lecture 7 — The cause on the part of matter why generation never fails.

We must therefore concentrate all our powers on the discussion of these difficulties and on the solution of a further question—viz. what is the cause of the perpetuity of coming-to-be? Why is there always unqualified, as well as partial, coming-to-be?

"Cause" in this connexion has two senses. It means (i) the source from which, as we say, the process 'originates', and (ii) the matter. It is the material cause that we have here to state.

For, as to the other cause, we have already explained (in our treatise on Motion that it involves (a) something immovable through all time and (b) something always being moved. And the accurate treatment of the first of these—of the immovable 'originative source'—belongs to the province of the other, or 'prior', philosophy: while as regards 'that which sets everything else in motion by being itself continuously moved', we shall have to explain later' which amongst the so-called 'specific' causes exhibits this character. But at present we are to state the material cause—the cause classed under the head of matter—to which it is due that passing-away and coming-to-be never fail to occur in Nature. For perhaps, if we succeed in clearing up this question, it will simultaneously become clear what account we ought to give of that which perplexed us just now, i.e. of unqualified passing-away and coming-to-be.

Our new question too—viz. 'what is the cause of the unbroken continuity of coming-to-be?'—is sufficiently perplexing, if in fact what passes-away vanishes into 'what is not' and 'what is not' is nothing (since 'what is not' is neither a thing, nor possessed of a quality or quantity, nor in any place). If, then, some one of the things 'which are' constantly disappearing, why has not the whole of 'what is' been used up long ago and vanished away assuming of course that the material of all the several comings-to-be was finite?

For, presumably, the unfailing continuity of coming-to-be cannot be attributed to the infinity of the material. That is impossible, for nothing is actually infinite.

A thing is infinite only potentially, i.e. the dividing of it can continue indefinitely: so that we should have to suppose there is only one kind of coming-to-be in the world—viz. one which never fails, because it is such that what comes-to-be is on each successive occasion smaller than before. But in fact this is not what we see occurring.

Why, then, is this form of change necessarily ceaseless? Is it because the passing-away of this is a coming-to-be of something else, and the coming-to-be of this a passing-away of something else?

52. After presenting an objection against the aforesaid solution, the Philosopher here introduces another question, the answer to which resolves the previous objection. About this he does two things:

first, he introduces the question and resolves it;

second, he uses this solution to resolve the main question, at the cause implied in this solution (318a25; [58]).

With respect to the first he does three things:

first, he presents the question;

second, he tackles the question, at our new question too (318a13; [54]);

third, he resolves it, at why, then, is this form (318a24; [57]).

Regarding the first he does two things.

First he introduces the question (317b33) and says that these, namely, the previous objection should be handled to the extent that the proposition requires, and that, in order to get a better understanding, we should inquire into the reason why generation always exists, i.e., both absolute generation and generation with respect to a part, i.e., generation in a qualified sense. Now those who posit that the world and motion are perpetual must also posit perpetual generation. What the force of Aristotle's arguments is with regard to the perpetuity of motion and the eternity of the world we have explained in Physics VIII and in On the Heavens I.

53. Second, at "cause" in this connexion (318a1), he explains the question he has introduced and says that one cause that may be assigned of the eternity of generation is that which is called whence the principle of motion comes, i.e., the moving or efficient cause; another cause may be assigned, which is matter. And this is the one to be assigned now, namely, the material—for the moving cause has been discussed in the tract on motion, i.e., in Physics VIII, where it was said that there exists a certain immobile mover for all time, namely, the mover of the heavens, and a mover which is always moved, namely, the heavens.

To determine concerning one of these, namely, the first mover, pertains to another part of philosophy, the part which is first among all the parts; hence in Metaphysics XII the Philosopher determined concerning the cause of the perpetuity of motion and of generation. But regarding the other mover, namely, the mover which causes perpetual generation because it is itself continually being moved, it will later be assigned, at the end of the present book, how this is the cause of each of the aforesaid, i.e., of the perpetuity of generation absolutely speaking and in the qualified sense.

But now we must assign the cause why in perpetuity, generation and corruption do not desert nature, and which is the cause classed under the head of matter, namely, the material cause. And lest this seem to be foreign to the proposition, he adds that perhaps it will at the same time be shown both what must be said about this question and what must be said of absolute generation and corruption.

54. Then, at our new question too (318a13), he pursues the question brought up.

First, he presents an objection that would deny perpetuity of generation;

second, he rejects some answers to this objection, at for, presumably (318a19; [55]).

He says therefore first (318a13) that there seems to be sufficient reason to inquire as to the cause why generation is folded around, i.e., eternally revolves in nature, if that which is corrupted absolutely falls into non-being. For just as what is generated absolutely comes to be from non-being absolutely, so what is corrupted absolutely would seem to fall into non-being absolutely, in the sense that this non-being would be absolutely nothing. For that into which it falls cannot be a something, i.e., a substance, for since absolute corruption is of substance, what is corrupted absolutely must fall into non-substance. Consequently, neither can the non-being at which corruption ends be quality, or quantity, or "where," or any of the other predicaments, since accidents cannot exist without substance.

If, therefore, generation and corruption go on forever, it seems that some being will always be falling into non-being. Consequently, there is always being subtracted some one or other of the things having natures. Now, it is plain that whatever is finite will be consumed if something is continually removed from it. Hence, if the whole universe, from which each and every being is generated, is finite, and if generation is from eternity, then all being should have been exhausted long ago, so that nothing should be left now but emptiness, i.e., the void.

55. Then, at for, presumably (318a19), he excludes two answers.

The first was that of the ancient natural philosophers who, in order to account for the perpetuity of generation, attributed infinity to the principles. For all who posited one principle, such as fire or air or water or something in-between, endowed that principle with infinity. Democritus however assumed infinite empty space, as well as an infinitude of indivisible bodies. Likewise, Anaxagoras posited an infinitude of similar parts as principles.

All these tenets are rejected by the Philosopher, who says that it cannot be that the reason why generation does not cease is because that is infinite from which something is generated, whether there be one principle or many principles. For such a thing is impossible, since, as was proved in Physics III and in On the Heavens I, there is in nature no infinite in act.

56. A second answer is now presented and refuted, at a thing is infinite (318a21). For someone could say that, although there is not present in nature any infinite in act, there is nevertheless an infinite in potency, as is evident in the division of a continuum. Consequently, someone could say that, just as, even though it is not infinite in act, something can be taken ad infinitum by division from a continuum without its being consumed, so too, from natural body, out of which all things are generated, even though it is not infinite, something can be taken which, by corruption, falls away to non-being, yet without its ever being totally consumed.

But this is excluded. For if, from a finite continuum, as is said in Physics III, the same quantity is always removed, it will, no matter how large, be finally consumed—for example, if one should continue to remove a palm's breadth from the diameter of the heaven. But a continuum is divided ad infinitum if subtraction is always made according to the same proportion — for example, if a continuum be divided in half, and the half into half, and so on infinitely. The same holds for any other ratio. Such a division having been made, it is plain that what is taken after the half will always be less than what was taken before—for the half of the half is always less than the half of the whole. Hence Aristotle concludes that, if this is the way that generation and corruption are to endure forever, i.e., in the way that a continuum is forever divided, then whatever is generated later will always have to be smaller in quantity, so that, by virtue of what is subtracted from natural body being always less, the original quantity will not be totally consumed. But we do not see this happen, namely, what is generated being always less. Consequently, the way generation and corruption endure ad infinitum cannot be similar to the division of a magnitude ad infinitum.

57. Then, at why, then, is this form (318a24), having rejected the false solutions, he concludes to the true one, namely, that the reason why the transmutation of generation and corruption must be unfailing, or unquiet, i.e., unceasing, is that the corruption of this is the generation of something else, and vice versa. For generation per se is indeed from a being in potency, i.e., from matter, which is as the subject of natural things—it is accidental to the matter out of which something is generated that it be the subject of another form, with respect to which it is being in act, and at the same time to the privation of the form to be induced, with respect to which it is non-being in act. On this account, Aristotle in Physics 1 says that generation is per accidens from a being in act but per se from a being in potency.

Similarly, a thing is per se corrupted into a being in potency, which indeed is now subject to another form, according to which it is a being in act, and to the privation of the previous form, with respect to which it is now non-being in act. Consequently it does not follow that what is corrupted departs completely from the whole nature of things, for although that which is corrupted becomes non-being, yet something else remains, namely, that which has been generated. Accordingly, matter cannot remain without being subjected to some form. That is why, upon the corruption of one thing, another is generated, and upon the generation of one thing another is corrupted. Consequently, there is in generation and corruption a certain cycle which gives it the aptitude to last forever.

Finally, he concludes with the summary that the aforesaid cause should be considered sufficient as to why there should be absolute generation and corruption with respect to each and every thing in perpetuity. This is true on the supposition that the world and motion are eternal—which, however, the Catholic faith does not suppose, as has been said elsewhere.