Lecture 12 — The first mover is immobile and one

Since there must always be motion without intermission, there must necessarily be something—one thing, or maybe a plurality—that first imparts motion, and this first mover must be unmoved.

Now, the question whether each of the things that are unmoved but impart motion is eternal is irrelevant to our present argument.

But there must necessarily be some such thing that, while it has the capacity of moving something else, is itself immobile with respect to any change from without, which can affect it neither in an unqualified sense nor in an accidental one.

If anyone likes, let us suppose that, in the case of certain things, it is possible for them at different times to be and not to be, without any process of generation and corruption (in fact, it would seem to be necessary, if a thing that has not parts at one time is and at another time is not, that any such thing should, without undergoing any process of change, at one time be and at another time not be).

And let us further suppose it possible that some principles that are unmoved but capable of imparting motion at one time are and at another time are not. Even so, this cannot be true of all such principles,

since there must clearly be something that causes things that move themselves at one time to be and at another not to be. For since something not divisible into parts can be in motion, that which moves itself must as a whole have magnitude, though nothing that we have said makes this necessarily true of every mover.

So, the fact that some things become and others perish, and that this is so continuously, cannot be caused by any one of those things that, though they are unmoved, do not always exist: nor again can it be caused by any of those that move certain particular things while others move other things.

The eternity and continuity of the process cannot be caused either by any one of them singly or by the sum of them, because this causal relation must be eternal and necessary, but the sum of these movers is infinite and they do not all exist together.

It is then clear that, though there may be countless instances of the corruption of some principles that are unmoved but impart motion, and though many things that move themselves perish and are succeeded by others that come into being, and though one thing that is unmoved moves one thing while another moves another,

there is nevertheless something that comprehends them, and that as something apart from each one of them and which is the cause of the fact that some things are and others are not and of the continuous change, and this causes the motion of the other movers, while they are causes of the motion of others.

Thus, motion being eternal, the first mover, if there is but one, will be eternal also; if there are more than one, there will be a plurality of such eternal movers.

We ought, however, to suppose that there is one rather than many, and a finite rather than an infinite number.

When the consequences of either assumption are the same, we should always assume that things are finite rather than infinite in number, since, in things constituted by nature, that which is finite and that which is better ought, if possible, to be present rather than the reverse.

Here it is sufficient to assume only one mover, the first of unmoved things, which, being eternal, will be the principle of motion to everything else.

The following argument also makes it evident that the first mover must be something that is one and eternal. We have shown that there must always be motion. That being so, motion must also be continuous, because what is always is continuous, whereas what is merely consecutive is not continuous.

But, further, if motion is continuous, it is one; and it is one only if the mover and the moved that constitute it are each of them one, for in the event of a thing’s being moved now by one thing and now by another, the whole motion will not be continuous, but successive.

1069. Having shown that, in things moved by another, there is no proceeding to infinity, but a first must be reached that is either immobile or a mover of self, and having shown that, of a thing that moves itself, one part is an immobile mover, and that, consequently, in either case, there is a first mover that is immobile, and because, among self-movers that exist among us (namely, perishable animals), it happens that the motion-causing part in the thing that moves itself—namely, the soul—is perishable and moved per accidens, the Philosopher now wishes to show here that the first mover is imperishable and is not moved either per se or per accidens.

About this, he does two things:

first, he proposes what he intends;

second, he proves it, at if anyone likes, let us suppose (258b16; [1072]).

About the first, he does three things:

first, he reviews what has been previously shown;

second, he passes over something that seemed useful for his proposition, at now, the question (258b12; [1070]);

third, he explains his proposition, at but there must necessarily (258b13; [1071]).

He says first (258b10) that it was shown above that motion always exists and never fails. (Lect. 1ff.) And, since all motion is from a mover, (Lect. 7.) and since in movers there is no proceeding to infinity, (Lect. 9.) it is necessary that there be a first mover. And, since it has not yet been proved that the first mover is one, he accordingly lets it remain doubtful whether it is one or many. Further, it has been shown that the first mover is immobile, (Lect. 11.) whether, by ascending from moved to movers, one immediately reaches a first immobile mover, or whether what is reached is a first mover that moves itself, one part of which is an immobile mover.

1070. Some have opined that all moving principles in things that move themselves are imperishable, for Plato posited all the souls of animals to be perpetual. And, if this opinion were true, Aristotle would have his proposition clinched at once, so far as the first mover’s being eternal is concerned. But the opinion of Aristotle is that, among the parts of the soul, only the intellect is imperishable, even though other parts of the soul are movers.

Consequently, he passes over this at now, the question (258b12), where he says that, as far as the present argument is concerned, it is of no moment whether each of the principles that move themselves and are immobile is imperishable, even though some have posited this by positing that all souls are imperishable. And he says that this does not affect the present argument, because he will prove his proposition without using this supposition.

1071. Then, at but there must necessarily (258b13), he explains what he intends to prove. And he says that, by considering the things that follow, it can be shown that, even though not every immobile mover is imperishable, there must be something immobile in such a way that it is in no way moved from without, either absolutely or per accidens, and yet is a mover of something else.

When he says, immobile with respect to any change from without, he does not mean to exclude a motion—that is, an operation—that is in the one operating in the sense that to understand is called a “motion,” and in the sense that the appetite is moved by the desirable object. A motion of this sort is not excluded from the first mover that Aristotle is discussing.

1072. Then, at if anyone likes, let us suppose (258b16), he proves what he had said, namely, that there exists a first mover that is eternal and entirely immobile.

First, he proves this through self-movers that at one time exist and at another time do not;

second, he proves through moving principles that sometimes are causing motion and sometimes not, at moreover, a conviction (259a21; [1077]).

About the first, he does three things:

first, he shows that there must be a first mover that is eternal;

second, he shows that such a mover should be one rather than many, at we ought, however (259a8; [1075]);

third, he shows both at once—that is, that there is one first mover, and that it is eternal—at the following argument (259a13; [1076]).

About the first, he does two things:

first, he rejects an argument by which some could try to prove this proposition;

second, he goes on to explain his proposition, at since there must clearly (258b22; [1074]).

1073. Now, someone could proceed as follows (258b16). Whatever cannot be at one time and not be at another is eternal; but the first mover, since it is immobile (as has been shown above (Lect. 11, n. 1068.)), cannot be at one time and not be at another time, for whatever is such is generated and ceases to be, which involves its being moved. Therefore, the first mover is eternal.

But Aristotle does not have any use for this argument, because someone could say, if he wants, that it happens in some things that they exist at one time and they do not at another without their being generated or ceasing to be, speaking per se, and consequently without their being moved per se. For if something not divisible into parts, namely, something not composed of matter and form, is at one time in a certain way and at another time is not, then necessarily, every such thing—without any self-change—does at one time exist and at another time not exist, as may be said of a point, and of whiteness, and of anything of this sort, for it has been shown in book 6 that whatever is moved can be divided into parts, (Lect. 5, n. 796ff.) and in Metaphysics 7 that whatever is generated is composed of matter and form. (Aristotle, Metaphysics Z.7–8; cf. St. Thomas, Commentary on Metaphysics, bk. 7, lect. 6–7.) Such non-divisible things, therefore, are neither generated nor changed per se, but per accidens, when other things are generated or changed.

From this, it is also plain that, if something is moved neither per se nor per accidens, it is eternal, and that, if it is eternal, it is moved neither per se nor per accidens, insofar as it is eternal. If, therefore, it is conceded that it is contingent that something exist at one time and not at another without its being generated or ceasing to be, then let it also be conceded to be contingent that certain immobile moving principles that are yet mobile per accidens exist at one time and do not exist at another. Nevertheless, it is not at all possible that all such principles that are movers and immobile be such that they exist at one time and not exist at another.

1074. Then, at since there must clearly (258b22), he proves his proposition. And he says that, if some things that move themselves exist at one time and not at another, then there must be a cause of their generation and ceasing to be, by virtue of which they exist at one time and do not exist at another, because whatever is moved has a cause of its motion. But what exists at one time and not at another, if it is a composite, is generated and ceases to be. Now, a thing that moves itself must possess magnitude, since it is moved, and it has been shown in book 6 that nothing indivisible into parts is moved. (Lect. 5, n. 796ff.; cf. lect. 12.)

But, from the foregoing, it cannot be held that it is necessary for the mover to have magnitude, (Cf. lect. 11, nn. 1064–65.) and thus it is not moved per se, if it exists at one time and does not exist at another. But, if there is a cause of the generation and corruption of things that move themselves, then there must also be a cause to account for their generation and corruption being continued forever.

But it cannot be said that the cause of this continuity is one of those immobiles that do not always exist, nor can it be said that the causes of the eternal generation and corruption of some things that move themselves are certain immobile movers that do not always exist and that the causes of other such generations and corruptions are certain other such immobile movers. And he explains this when he says that not one, nor all of them, can be the cause of this continuous and eternal generation.

That one of them cannot be the cause he thus proves. What does not exist forever cannot be the cause of what is always, perpetual, and necessary. That all cannot be the cause he proves by the fact that all such perishable principles, if generation is perpetual, are infinite and do not all exist at once. But it is impossible for one effect to depend on an infinitude of causes.

And again, things that do not exist at once cannot be the cause of one thing, although it could be said that, when things do not exist all at once, some dispose and some cause, as is plain with respect to drops that fall successively and wear away a stone. But, if a number of things are a direct cause of anything, they must exist all together.

Accordingly, it is manifest that, if there are a million principles that are movers and immobile, and if there are many things that move themselves, of which some perish and others come to be, and among these, some are mobile and some movers, nevertheless there must be something above all of them that, by its power, contains all the things that are generated and perish in the above-mentioned way and that would be the cause of the continual change affecting them by which they sometimes are and sometimes are not and through which these latter are the causes of coming to be and of motion for others, with these others being the cause for yet others.

For every generator is a cause of generation to the thing generated, but it is from some imperishable first principle that perishable generators possess the characteristic of being causes of generation. If, therefore, the motion through which some things at one time exist and at another do not is perpetual, as has been shown above, (Lect. 1ff.) and a perpetual effect cannot exist except from a perpetual cause, then, necessarily, the first mover is perpetual, if it is one; and if there are more than one first movers, they too are perpetual.

1075. Then, at we ought, however (259a8), he shows that one perpetual principle ought to be posited rather than many. And he says that, just as finite principles ought to be preferred to infinite ones, (Cf. bk. 1, lect. 9, 11.) so should one first principle be preferred rather than many. For if the same effects happen or follow from positing finite principles as from positing infinite principles, one should assume that the principles are finite rather than infinite, for in things that are according to nature, the preference must be given to what is better, if it is possible, because things that are according to nature are disposed the best. Now, a finite principle is better than an infinite one, and one is better than many. But one first immobile principle, if it is perpetual, is sufficient for causing the perpetuity of motion. Therefore, many first principles should not be posited.

1076. Then, at the following argument (259a13), he concludes from the foregoing that it is necessary that there be one first mover that is imperishable. And, although this seems to be sufficiently proved from the foregoing, yet someone could cavil that the cause of the continuity of generation is a perpetual first self-mover whose own mover is not perpetual and one, but is rather diverse movers, some of which cease to be and some of which come to be. But he intends to dismiss this, for if motion is perpetual, as he had proved above, (Lect. 1ff.) then necessarily the motion of the first self-mover, which is posited as the cause of the entire perpetuity of motion, is eternal and continuous. For if it were not continuous, it would not be eternal. However, what is successive is not continuous, but in order that a motion be continuous, it must be one; and in order to be one, it must be from one mover and in one mobile. But, if the mover is different, the motion will not be a whole continuous motion, but a successive one. Therefore, it is absolutely necessary that the first mover be one and perpetual. But an immobile mover that is moved per accidens is not perpetual, as has been said above. It remains, therefore, that the first mover is utterly immobile, both per se and per accidens.