Lecture 9 — Not every mover must be moved

Now, this may come about in either of two ways.

Either the mover moves not on its own account, which is to be referred to something else that moves the mover, or the mover moves on its own account.

Further, in the latter case, either the mover moves the next to last thing or there may be one or more intermediate links.

For instance, the stick moves the stone and is moved by the hand, which again is moved by the man; in the man, however, we have reached a mover that is not so in virtue of being moved by something else.

Now, we say that the thing is moved both by the last and by the first mover in the series, but more strictly by the first, since the first mover moves the last, whereas the last does not move the first, and the first will move the thing without the last, but the last will not move it without the first. For instance, the stick will not move anything unless it is itself moved by the man.

If, then, everything that is in motion must be moved by something and the mover must either itself be moved by something else or not, and in the former case there must be some first mover that is not itself moved by anything else, while in the case of the immediate mover being of this kind there is no need of an intermediate mover that is also moved

(for it is impossible that there should be an infinite series of movers, each of which is itself moved by something else, since, in an infinite series, there is no first term), then if [as was said] everything that is in motion is moved by something and the first mover is moved but not by anything else, it must be moved by itself.

This same argument may also be stated in another way as follows.

Every mover moves something and moves it with something, either with itself or with something else.

For instance, a man moves a thing either himself or with a stick, and a thing is knocked down either by the wind itself or by a stone propelled by the wind.

But it is impossible for that with which a thing is moved to move it without being moved by that which imparts motion by its own agency.

On the other hand, if a thing imparts motion by its own agency, it is not necessary that there should be anything else with which it imparts motion.

Whereas if there is a different thing with which it imparts motion, there must be something that imparts motion not with something else, but with itself, or else there will be an infinite series.

If, then, anything is a mover while being itself moved, the series must stop somewhere and not be infinite. Thus, if the stick moves something in virtue of being moved by the hand, the hand moves the stick; and, if something else moves with the hand, the hand also is moved by something different from itself.

So, when motion by means of an instrument is at each stage caused by something different from the instrument, this must always be preceded by something else that imparts motion with itself.

Therefore, if this last mover is in motion and there is nothing else that moves it, it must move itself.

So, this reasoning also shows that, when a thing is moved, if it is not moved immediately by something that moves itself, the series brings us at some time or other to a mover of this kind.

And, if we consider the matter in yet a third way, we shall get this same result as follows.

If everything that is in motion is moved by something that is in motion, either this being in motion is an accident of the movers in question (such that each of them moves something while being itself in motion, but not always because it is itself in motion) or it is not accidental, but an essential attribute.

Let us consider the former alternative. If, then, it is an accident, it is not necessary that that which causes motion should be in motion; and, if this is so, it is clear that there may be a time when nothing that exists is in motion, since the accidental is not necessary, but contingent.

Now, if we assume the existence of a possibility, any conclusion that we thereby reach will not be an impossibility, though it may be contrary to fact. But the non-existence of motion is an impossibility, for we have shown above that there must always be motion.

Moreover, the conclusion to which we have been led is a reasonable one.

For there must be three things—the moved, the mover, and the instrument of motion.

Now the moved must be in motion, but it need not move anything else.

The instrument of motion must both move something else and be itself in motion (for it changes together with the moved, with which it is in contact and continuous, as is clear in the case of things that move other things locally, in which case, the two things must up to a certain point be in contact).

And the mover—that is to say, that which causes motion in such a manner that it is not merely the instrument of motion—must be unmoved.

Now we have visual experience of the last term in this series, namely, that which has the capacity of being in motion but does not contain a motive principle, and also of that which is in motion but is moved by another and not by itself.

It is reasonable, therefore—not to say necessary—to suppose the existence of the third term also, that which causes motion but is itself unmoved.

So, too, Anaxagoras is right when he says that Mind is impassive and unmixed, since he makes it the principle of motion, for it could cause motion in this sense only by being itself unmoved, and could have supreme control only by being unmixed.

We will now take the second alternative. If the motion is not accidentally in motion, but necessarily—such that, if it were not in motion, it would not move anything—then the mover, insofar as it is in motion, must be in motion in one of two ways. It is moved as that is that is moved either with the same kind of motion, or with a different kind.

I mean that either what is heating is itself becoming hot, what is making healthy is becoming healthy, and what is causing locomotion is in the process of locomotion,

or else what is making healthy is in the process of locomotion, and what is causing locomotion is in the process of increase.

But it is evident that this is impossible.

For if we adopt the first assumption, we have to make it apply within each of the individual species into which motion can be divided.

For instance, we must say that, if someone is teaching some lesson in geometry, he is also in process of being taught that same lesson in geometry, and that, if he is throwing, he is in process of being thrown in just the same manner.

Or if we reject this assumption, we must say that one kind of motion is derived from another: for instance, that what causes locomotion is increase; what causes increase is being altered by something else; and what causes this alteration is the suffering of some other kind of motion.

But the series must stop somewhere, since the kinds of motion are limited.

And if we say that it’s reversible and that what causes alteration is in the process of locomotion, this is the same as saying that what causes locomotion is in the process of locomotion and that one teaching is being taught.

For it is clear that everything that is moved is moved by the mover that is further back in the series as well as by that which immediately moves it; in fact, the earlier mover is that which more strictly moves it.

But this is, of course, impossible, for it involves the consequence that one who is teaching is in process of learning what he is teaching, whereas teaching necessarily implies possessing knowledge, and learning implies not possessing it.

Still more unreasonable is the consequence involved that, since everything that is moved is moved by something that is itself moved by something else, everything that has a capacity for causing motion has as such a corresponding capacity for being moved—

that is, it will have the capacity to be moved in the sense in which one might say that what has a capacity for making healthy and exercises that capacity has, as such, a capacity for being made healthy,

or that what has a capacity for building has as such a capacity for being built.

It will have the capacity for being thus moved either immediately or through one or more links.

(As it will if, while everything that has a capacity for causing motion has as such a capacity for being moved by something else, the motion that it has the capacity for suffering is not that with which it affects what is next to it, but a motion of a different kind;

for instance, that which has a capacity for making healthy might as such have a capacity for learning, but the series could be traced back, as we said before, until, at some time or other, we arrived at the same kind of motion).

Now, the first alternative is impossible, and the second is fantastic: it is absurd that what has a capacity for causing alteration should as such necessarily have a capacity, let us say, for increase.

It is not necessary, therefore, that what is moved should always be moved by something else that is itself moved by something else.

Therefore, there will be an end to the series. Consequently, the first thing that is in motion will derive its motion either from something that is at rest or from itself.

But, if there were any need to consider which of the two (that which moves itself or that which is moved by something else) is the cause and principle of motion, everyone would decide the former.

For that which is itself independently a cause is always prior as a cause to that which is so only in virtue of being itself dependent upon something else that makes it so. We must, therefore, make a fresh start and consider the question: if a thing moves itself, in what sense and in what manner does it do so?

1037. After showing that whatever is moved is moved by another, the Philosopher now begins to show that it is necessary to reach a first immobile mover.

And his treatment is divided into two parts.

In the first, he shows that it is necessary to reach a first that either is immobile or moves itself;

in the second, he shows that, even if a first that moves itself is reached, it is further necessary to reach a first mover that is immobile, at now, everything that is (257a33; [1050]).

About the first, he does two things:

first, he shows that it is not possible that things be moved by another to infinity;

second, he shows that not every mover need be moved, at and, if we consider (256b3; [1042]).

About the first, he does two things:

first, he explains the proposition by ascending in the order of mobiles and movers;

second, he shows it by descending, at this same argument (256a21; [1041]).

About the first, he does two things:

first, he sets out things needed for manifesting his proposition;

second, he gives an argument that shows the proposition, at if, then, everything (256a13; [1040]).

1038. Now, he sets down two things, of which the first (256a4) is a division of movers.

For since it has been said that whatever is moved is moved by something, (Lect. 7, n. 1024ff.) a thing might be a mover in two senses.

In one sense, it moves not on its own account, that is, not by its own power, but because it has been moved by some other mover. This is a second mover.

In another sense, something moves on its own account, that is, by its own power and not because it has been moved by another.

Now, such a mover can cause motion in two ways.

First, it can do so in such a way that the first mover moves the one next to last, that is, the one that is nearest to it after the second mover. This happens when the first mover moves a mobile through just one intermediate.

Second, it can cause motion in such a way that the mover moves a mobile through a number of intermediates, as when a stick moves a stone and the stick is moved by a hand, which is moved by a man who does not move as being moved by something else.

In this way, the man is a first mover on his own account and he moves the stone through a number of intermediates; however, if he moved the stone with his hand, he would be moving the stone through one intermediate only.

1039. Second, at now, we say (256a8), he compares the first mover with the second. For when we say that the first mover moves as much as does the ultimate mover, we say that the first mover is more a mover than the ultimate mover.

This is clear for two reasons:

first, because the first mover moves the second mover but not vice versa;

second, because the second mover cannot cause motion independently of the first, but the first can cause it independently of the second. For example, the stick cannot move the stone unless it is moved by the man, but the man can move the stone without using the stick.

1040. Then, at if, then, everything (256a13), he proves his proposition in the light of the foregoing. For it has been shown that whatever is being moved is being moved by another. (Lect. 7, n. 1024ff.) But that by which it is moved is itself either moved or not moved; and if it is moved, it is either moved by another or not. Now, these two—namely, being moved by another and not being moved by another—are such that, if one is posited, the other must be, but not vice versa: that is, if there is something that is moved by another, it is necessary to come to a first that is not moved by another; but if such a first is posited (namely, a first that is not moved by another), it is not necessary further to posit another (namely, one that is moved by another).

This, indeed, is self-evident, but there could be some doubt about the first one, namely, that, if there be found something moved by another, there will be found a first that is not moved by another. For this reason, he proves this in the following manner.

If something is moved by another, and this in turn by another, and if something not moved by another is never reached, it follows that there is a process to infinity in movers and moved things. But this is impossible, as was proved in book 7. (Lect. 2.) However, he here proves it in a more certain way from the fact that there is no first in an infinite series. Therefore, if movers and moved things go on to infinity, there will be no first mover. But it has already been said that, if the first mover does not act, the last mover does not act and, consequently, there will be no mover, which is clearly false. Therefore, the process of something being moved by another cannot go on to infinity. If, therefore, it be conceded that whatever is being moved is being moved by another, as has been proved, and again, if it be supposed that the first mover is itself being moved but not by something else, it is necessarily being moved by itself.

It should be noted that this argument is not proving that the first mover is being moved, but he is supposing this according to the common opinion of the Platonists. As to the force of the argument, it does not prove that the first mover moves itself more than it proves that it is immobile. Hence, he later presents this same conclusion under a disjunction, as will be clear below.

1041. Then, at this same argument (256a21), he proves his proposition by descending. And it is the same argument as the preceding so far as its inferential value is concerned, but differs with respect to the order of the process; he repeats it, however, for the sake of greater clarity.

He says therefore that the previous argument might be presented in another way. And he sets down propositions that have the same account of truth as the previous ones, but in a different order. For above he had argued that whatever is being moved is being moved by another, and that that by which it is moved acts either on its own account or on account of something else previously moving it; and this was an ascending process.

But he now uses a descending process, saying that every mover moves something and moves by means of something, that is, either by itself or by means of some lesser mover, as a man moves a stone either by himself or by means of a stick and the wind casts something to the earth either by its own impulse or by means of a stone that it moves.

Again, he had argued above that the last mover does not cause motion independently of the first mover, but vice versa. In place of that, he here says that what a mover uses as an instrument in causing motion cannot itself cause motion without a principal mover moving it, as a stick cannot cause motion independently of the hand. But, if something moves by itself as a principal mover, the addition of an instrument is not required.

And this is more evident in instruments than in an ordered array of mobiles, although the same truth is present in both cases, because not everyone would consider the second mover an instrument of the first. But, just as he deduced above that, if there is something that is being moved by another, there must be something that is not being moved, but not vice versa, so here in a descending process he says that, if that by which the mover causes motion is another thing, as an instrument, there has to be something that causes motion not by an instrument, but by itself. Otherwise, there is an infinite process with respect to instruments, which is the same as proceeding to infinity with respect to movers, and that is impossible, as has been proved above.

If, therefore, there exists a mover of that which is being moved, a halt must be made and the process cannot go to infinity. For if the stick causes motion because it is moved by the hand, it follows that the hand moves the stick; if, however, something else is moving the hand, it also follows conversely that a mover is moving the hand. Consequently, the same process that was valid with respect to moved instruments is valid for movers of instruments. But, with respect to movers, as was shown, an infinite process must be avoided; therefore, it must be avoided with respect to instruments. Therefore, since it is always such that a thing being moved is moved by another that moves, and an infinite process must be avoided, it is necessary that there be a first mover that moves by itself and not through an instrument.

If, therefore, it be granted that this first that moves itself is indeed moved but there is no other moving it (because then it would be an instrument), it follows of necessity that it is moving itself—following the supposition of the Platonists that every mover is moved. Hence, also according to this argument, either what is being moved will be immediately moved by a mover that moves itself or, at some time, such a mover that moves itself must be reached.

1042. Then, at and, if we consider (256b3), he shows that not every mover is being moved, as was supposed in the preceding arguments.

About this, he does two things:

first, he proves that not every mover is being moved;

second, from this and from the previous arguments, he argues for his main proposition, at it is not necessary (257a25; [1049]).

He therefore says first that to the above-mentioned things may be added the following in order to show our proposition.

About this, he does three things:

first, he gives a division;

second, he rejects one member, at let us consider (256b7; [1043]);

third, he rejects another, at we will now take (256b27; [1046]).

He says first (256b3) that, if whatever is being moved is being moved by another—which is tantamount to saying that every mover is moved—this can be in two ways:

in one way, that it is per accidens in things that a mover is moved, that is, the mover does not act in virtue of being moved (as if we should say that a musician is a builder not because he is a musician, but per accidens);

or, in a second way, that it is not per accidens but per se that a mover is moved.

1043. Then, at let us consider (256b7), he rejects the first member in three ways.

First, with this argument. Nothing per accidens is necessary, for what is in a thing per accidens is not present of necessity, but may happen not to be present, as musician in a builder. If, therefore, it is per accidens that movers are moved, it follows that it can happen that they not be moved. But once you posit that every mover is moved, it is a consequence, if movers are not moved, that they do not cause motion. It follows, therefore, that, at some time, nothing is being moved.

But this is impossible, for it has been proved above that it is necessary that motion always exist. (Lect. 1ff.) This impossibility, however, does not follow from the supposition that movers are not moved; for if it is per accidens that a mover is moved, it will be possible for movers not to be moved, and if a possibility is posited, no impossibility follows. It remains, therefore, that the other statement from which it followed is impossible, namely, the statement that every mover is moved.

1044. Second, at moreover, the conclusion (256b13), he proves the same with another probable argument, which is this. Three things are found in motion:

one is the mobile that is being moved;

another is the mover;

and the third is the instrument by which the mover causes motion.

Now, among these three, it is clear that the thing that is moved has to be moved, but it does not have to cause motion. But the instrument by which the mover causes motion must both move and be moved: it is moved by the principal mover and it moves the last thing moved. For this reason, whatever moves and is moved has the character of an instrument.

Now, the reason that the instrument by which the mover causes motion both is moved and moves is that it partakes of both and exists in a sort of identity with what is moved. This is especially evident in local motion, for it is necessary that, from the first mover to the last thing moved, all must touch one another. Accordingly, it is evident that an intermediate instrument is the same as the mobile through contact and is moved at once with it, insofar as it is in union with it. But it is also in union with the mover, because it is a mover—even though, under its aspect as the instrument by which the mover causes motion, it is not immobile.

Accordingly, therefore, it appears from the premises that the last thing moved is indeed being moved, but it does not have in itself a principle for moving either itself or anything else, and it is moved indeed by something else and not by itself.

Hence, it seems to be reasonable, that is, probable (and, in the present case, we do not care to say that it is necessary), that there be a third thing that causes motion but is immobile.

For it is probable that, if two things are joined per accidens and one is found without the other, then the other might be found without it.

But that it may be found without the other is necessary, because things joined per accidens may happen not to be joined; for example, if white and sweet are joined per accidens in sugar, and if white is found without sweet, as in snow, it is probable that sweet be found in something without white, as in cinnamon. If, therefore, it is per accidens that a mover be moved, and something is found to be moved without moving something else, as happens in the last thing moved, it is probable that one may find moving without being moved, such that there would be a mover that is not moved.

From this, it is evident that this argument does not have force in regard to substance and accident, and in matter and form, and in like things, of which one is found without the other but not vice versa; for accident per se exists in a substance, and to matter it belongs per se to have existence through form.

1045. Third, at so, too, Anaxagoras (256b24), he proves the same point on the testimony of Anaxagoras. For since it may be that a mover be found that is not moved, Anaxagoras spoke aright when he said that mind is impassible and unmingled. He said this because he posited mind as the first principle of motion, and the only way it could cause motion and command without itself being moved was that it be unmingled, since what is mingled with something else is in a certain way moved when that something else is moved.

1046. Then, at we will now take (256b27), he concentrates on the other part of the division, that whatever is moved is being moved by another that is moved per se and not accidentally.

And he disproves this with two arguments.

The first is this. If it is not according to an accident that a mover be moved, but of necessity, and if it can never cause motion unless it is moved, this must happen in one of two ways:

one is that the mover is moved according to the same species of motion as that which it causes;

the other is that the mover moves according to one species of motion and is moved according to another.

He subsequently explains the first way at I mean that either that which is (256b31). We say that a mover is being moved according to the same species of motion if, for example, the thing that causes heating is heated, the healer is healed, or something carrying locally is itself being carried locally.

He explains the second way at or else what is making healthy is in the process of locomotion, and what is causing locomotion is in the process of increase. These are examples of moving and being moved according to different species of motion.

Then he shows the impossibility of the first way, at but it is evident (256b34). For it is clearly impossible that a mover be moved according to the same species of motion. For it is not sufficient to stop at some subalternate species, but one must divide until he reaches the individual species, that is, the most specific species. For example, if someone is teaching, it is not enough for him simply to be taught at the same time, but he must be teaching and being taught the same; for instance, if he is teaching geometry, he must be at the same time being taught it; or if he is the cause of a local motion called “throwing,” he must himself be moved according to the same motion of throwing. This is clearly false.

Then he dismisses the second way, that the mover not be moved according to the same species of motion but that it move according to one species and be moved according to another, such as if it moves with a local motion and is being moved with respect to growth, or if what causes the growth is being moved by something else according to alteration, or if this mover in turn is being moved with respect to some other motion.

Now, it is clear that motions are not infinite either in genus or species. For it was held in book 5 (Lect. 6, n. 696ff.) that motions differ in genus and species according to the differences of the species in which motion occurs. But the genera and species of things are not infinite, as we proved elsewhere; (Cf. bk. 3, lect. 12, n. 394.) accordingly, neither are the genera and species of motion. If, therefore, a mover is necessarily being moved according to some other genus or species of motion, one will not be able to proceed to infinity and there will be some first immobile mover.

1047. But, because someone could say that, when all the species of motion are exhausted, a return will be made to the first species in such a way that, if the first thing taken as moved was moved locally and we distributed all the genera and species of motion to different movers until these genera and species were exhausted, the remaining mover will then be moved according to local motion:

in order to exclude someone saying this, he subsequently says that such a return is tantamount to saying that the cause of alteration is being moved locally (he uses this explanation because above, in his example, he mentioned local motion first and alteration last), the same, I say, as supposing from the very beginning that the mover according to local motion is being moved or that the teacher is being taught not only generically, but specifically.

And that this means nothing more, he proves consequently. For whatever is being moved is moved more by the higher mover than by the lower one, and consequently, much more so by the first mover.

If, therefore, the thing posited as being moved locally is being moved by a neighboring mover that is being increased, and it by a mover that is being altered, and it further by one that is being moved according to place, what is being moved according to place will be more moved by the first one moved according to place than by the second one that is being altered or by the third one that is being increased.

Therefore, it will be true to say that the mover according to place is being moved according to place, and the same for every species of motion. Now, not only is this false, because it is seen to be belied in many cases, but it is also impossible. For it would follow that the teacher is learning while he is teaching—which is impossible. For this involves a contradiction, since it is the property of a teacher that he have science, and of a learner that he not have it. Accordingly, it is clear that it is not necessary for a mover to be moved.

1048. He gives a second argument at still more unreasonable (257a14), which does not differ from the preceding one except in that the first leads to certain particular inconsistencies, for example, that a thrower would be thrown or that a teacher would be being taught. But this one leads to inconsistencies in general.

Hence, he says that, although it is inconsistent that a teacher be learning, there is something still more unreasonable, for it turns out that every mover is mobile, if nothing is moved except by what is being moved. For it will thus follow that every mover is mobile, if (for example) one says that whatever has the power to heal, or is actually causing health, is healable, and that whatever has the power to build is buildable—which is more unreasonable than that a teacher be learning, for a teacher could have been learning before, but a builder was never built.

Now, this follows in two ways.

For if it be conceded that every mover is being moved with respect to the same species of motion, it follows that a builder is being built immediately (that is, without intermediary) and that a healer is being healed immediately.

But, if it be conceded that the mover is not being moved according to the same species of motion, it follows that we shall finally come to this after passing through a number of intermediates.

And he explains this. If every mover is being moved by another but not being moved immediately with respect to the same species in which he is causing motion, but according to some other species—for example, if a healer is not at once being healed, but is being moved according to the motion of discipline by learning—yet, since the species of motion are not infinite, by thus ascending from mobile to mover, one will at length reach the same species of motion, as was explained above.

Therefore, of these two, one appears plainly impossible, such as that the builder be immediately being built, while the other is seen as a fantasy, namely, that one come to the same thing through a number of intermediates. For it is unacceptable that what is apt to cause alteration is of necessity apt to be increased in size.

1049. Accordingly, having considered the foregoing arguments (257a25), the first of which concluded that this process—that whatever is being moved is being moved by another—must not go on to infinity, and the second of which concluded that not every mover is being moved, we can conclude from all the foregoing arguments that it is not necessary to infinity that what is being moved be moved by another in such a way that it is always being moved by a mover that is being moved. Therefore, it is necessary to stop at some first. However, this first must either be immobile or be moving itself.

But, if we are considering which is the first cause of motion in the genus of mobiles, whether it is something that moves itself or a mobile that is moved by another, it is held as probable among all that the first mover moves itself. For a per se cause is always prior to what is a cause through another. For this reason, the Platonists held that, prior to things that are moved by another, there is something that moves itself.

And we must therefore consider this thing that moves itself and make of this another beginning of our consideration—that is, we must consider how something moving itself is possible.