Lecture 9 — The principles of movement in living beings: what they are

It seems that these two are the movers: either appetite or intellect (if one is to account imagination as a sort of intelligence). For many people follow the imaginations instead of intellectual knowledge, while in the other animals there is no intelligence or reason at all, but only imagination. Both of these effect movement in place, then—intellect and appetite.

Now, the intellectual power that reasons for the sake of something is practical, but it differs from the speculative by its end.

Every appetite also is for the sake of something; for what the appetite is for is the practical intellect’s starting point, and the last thing is the starting point of the action.

Hence, it seems reasonable that both appetite and the practical intellect are movers. For the object of appetite causes the motion, and because of this the intellect also causes the motion, since its own principle is the object of appetite. And when imagination causes the motion, it only does so with appetite.

Therefore there is one mover—the object of the appetite. For if there are two movers, intellect and appetite, they were causing the motion at least in virtue of some common species. However, the intellect does not now seem to be a mover without the appetite; for the will is an appetite. But when there is movement according to reason, there is also movement according to will. However, an appetite does cause movement against reason, for concupiscence is a sort of appetite.

All understanding, then, is right, but appetite and imagination may be right or not right. Hence, the object of appetite is indeed always what causes motion, but this is a good or an apparent good—not every good, however, but the practical good. Now, a practical object is possible and able to be other than it is. It is, therefore, evident that such a power of the soul, which is called “appetite,” causes the motion.

For those who divide the soul into parts, if they divide and separate it according to its powers, a great many parts result: the vegetative, the sensitive, the intellectual, the deliberative, and lastly, the appetitive. For these differ from one another much more than do the concupiscible and irascible.

Since appetites do become contrary to one another, but this occurs when reason and desire are contrary, this occurs only in things that have a sense of time. For the intellect commands restraint on account of what will happen, whereas desire is for what is now present. For it seems that what is pleasant right now is pleasant simply speaking, and good simply speaking, on account of the fact that the future is not seen.

The mover, therefore, will be specifically one—the object of appetite or the appetite itself, but the first of all things is the object of appetite; for this is what causes motion without itself being moved, by its being understood or imagined—but numerically, there are many movers.

Since there are these three: one, the mover; second, that by which it moves; third, that which is moved; and since the mover is twofold (the immobile one and the mover that is also moved), the immobile mover is, accordingly, the good in action, whereas that which moves and is moved is the appetitive power.

For what desires is moved insofar as it desires, and its appetite is certain act or movement. What is moved is the animal; that by which it moves is the organ of appetite, and this is right away something bodily. Hence, what pertains to it must be studied along with activities common to body and soul.

Now, in summary, organic movement arises where the principle and end are the same: as in the joint of a hinge are the convex and the concave: the latter being the end, and the former, the beginning. Hence one is at rest while the other is moved. They are distinct in account but inseparable in magnitude. For all things move by pushing and pulling. Hence there must, as in a circle, be something that stays still, from which point movement begins.

818. It seems that these two are the movers (433a9). So far the Philosopher has disputatively pursued his inquiry into what the principle of local movement in animals is; but now he determines the truth.

First, he shows in a universal way what that principle of motion is.

And second, at generally then (433b27; [836]), he shows how it varies in different subjects.

The first point again divides into two:

first, a statement of the principle of motion in animals;

and second, at the mover, therefore, will be specifically one (433b10; [830]), the order in which that motion is completed, in regard to the movers and the mobiles.

Again, the first subdivides into three points:

first, he posits that there are two principles of motion;

second, he reduces them to one, at now, the intellectual power (433a14; [820]);

and third, he answers an objection already raised, at since appetites (433b5; [829]).

First, then, he says that the foregoing examination makes it clear that neither the vegetative nor the sensitive part is the principle of movement, since they are found in things that do not move, as is clear from what has been said. (Lect. 8, nn. 808–11.)

It seems that these two are the movers: namely*, intellect* and appetite. Note, however, that he includes imagination under “intellect”; for it resembles intellect in that it moves one to action in the absence of sense-objects as does the intellect, because this too is a principle of motion.

819. For many men, in their own movements, follow their imagination, setting aside the knowledge of their intellect; for instance, those who are moved to do something by an impulse and do not act according to their reason. Besides, in the other animals it is obvious that there is no intellect or reason that can move them, but only imagination. Clearly, then, both of these effect movement: intellect, including imagination, and appetite.

820. Then, at now, the intellectual power (433a14), he reduces the aforementioned two movers to one; and this in three stages:

first, he shows the reduction;

second, at all understanding, then, is right (433a26; [826]), he uses what he has shown to assign the cause of a particular accidental factor in animal movements;

and third, he refutes an early division of the powers of the soul, at for those who divide (433a31; [828]).

First, then, he says that the intellect that moves one is the intellectual power that reasons for the sake of something, not for the sake of mere reasoning; and this is the practical intellect, which differs from the speculative by its end; for while the speculative contemplates the truth not for the sake of anything else, but only for its own sake, the practical intellect contemplates the truth for the sake of an activity.

821. Now, it is also obvious that every appetite is for the sake of something. For it is stupid to say that someone desires just for the sake of desiring; For desiring is a certain motion tending toward something else. Moreover, what the appetite is for, that is, the object of the appetite, is the practical intellect’s starting point; for that which is the first object of the appetite is the end from which the consideration of the practical intellect begins. For when we wish to deliberate about something among objects of action, we first lay down the end and then proceed through an order in inquire about things that should be done for the sake of the end, proceeding always from what comes later to what comes before, all the way to what is first at hand for us to carry out. So he adds that the last thing that the practical intellect considers is the starting point of the action—that is, that from which we should begin the action. This is why it is reasonable to assert that both appetite and the practical intellect are movers; for the object of appetite itself causes motion, and it is also what the practical intellect first considers; because of this, the practical intellect is said to cause the motion because, namely, its own principle, the object of appetite, moves it.

822. And what is said of the intellect should be understood also of the imagination, for when imagination causes motion, it does so only with the appetite; for, like the intellect, it moves only inasmuch as it represents an object of the appetite.

823. Therefore, it is clear that there is ultimately one mover—the object of the appetite. For this both moves the appetite and is the starting point of the practical intellect—which two were asserted to be the movers.

824. And it is reasonable that these two moving principles should be traced back to one thing, the object of appetite; for if there are two, intellect and appetite, that are posited as the movers of one and the same motion, they must move in virtue of some common species, since a single effect implies always a single proper cause. Now, it cannot be said that appetite moves under the intellect’s species, but rather the opposite, the intellect under the appetite’s species; for intellect is not found to be a mover without the appetite, for the will, according to which the intellect moves, is a sort of appetite.

825. The explanation of this, given in Metaphysics 9, is that, because the account of practical knowledge stands open to opposites, it does not initiate movement unless appetite determines it to one thing. (Aristotle, Metaphysics 9.5, 1048a8–16; cf. Aquinas, Commentary on Metaphysics, bk. 9, lect. 4, nn. 1820–22.) But an appetite, on the other hand, does cause movement without reason, as we see in those moved by concupiscence, for concupiscence is a sort of appetite. He mentions this desire rather than anger because anger has something belonging to reason, whereas concupiscence does not, as he shows in Ethics 7. (Aristotle, Ethics 7.6, 1149a25–b2; cf. Aquinas, Commentary on Ethics, bk. 7, lect. 6.) Clearly, then, the two movers are traced back to one, the object of appetite.

826. Next, at all understanding, then (433a26), he applies what has been said to a particular accidental factor in movement or action, explaining why we go amiss in our actions and movements. All understanding, he says, is right; this should be understood about the understanding of principles, for we never err in the understanding of the first principles in things that can be done; for example, no one should be harmed, nothing should be done unjustly, and so on. This is like the fact that we never err about the first principles in speculative things. But as for the consequences of these principles, if we consider them rightly, one proceeds based on the rectitude that surrounds the first principles, whereas if we deviate from that rectitude, one proceeds based on an error that happens in the reasoning. But appetite and imagination, which likewise cause motion, exist both with rectitude and without rectitude. This is why, in our actions, it is possible to deviate from rectitude insofar as we deviate from intellect and reason. Our previous conclusion stands, that the object of appetite is always what causes motion.

827. Now this object of appetite is either what is truly good, when it remains in the judgment of a correct understanding; or it is an apparent good, when appetite or imagination cause a deflection from that judgment. Not every good, however, is the object of appetite and a mover, but only the good that is able to be done, that is, a good as applied to action. And this is something that is able to be otherwise than it is, as are all things that are subject to our action; that is why the universal and necessary good, considered in its own universality, does not cause movement. Clearly, then, the power of the soul that is called “appetite” is the mover.

828. Then, at for those who divide (433a31), he rejects an old division of the motive parts of the soul into the rational, irascible, and concupiscible parts. If, he says, the intention is to enumerate the powers that are really distinct from each other, many others should have been included, namely, the vegetative, sensitive, intellectual, deliberative, and appetitive powers. (He distinguishes the deliberative power from the intellectual as, in Ethics 6, the reasoning power, which is about contingent things, is distinguished from the scientific, which is about necessary things, and for the reason that he touches on there.) (Aristotle, Ethics 6.1, 1139a11–15; cf. Aquinas, Commentary on Ethics, bk. 6, lect. 3.) All these parts of the soul differ from one another much more than the concupiscible and irascible, which are both included in the sensitive appetite. Hence, there are even more parts than they posited.

829. Next, at since appetites (433b5), he meets an objection already touched upon to show that appetite does not cause motion, namely, the continent do not follow their appetite. (Lect. 8, n. 817.) But this argument is resolved by the fact that in a man there are contrary appetites, of which the one the continent follow, and the rest they reject. He says, therefore, that since appetites do become contrary to one another, this happens when reason is contrary to concupiscence; and this occurs only in things that have a sense of time, that is, who are aware not only of the present moment but who consider the past and future as well. For sometimes intellect commands restraint from a certain desire on account of a consideration of what will happen in the future; thus a man with a fever, based on the judgment of his intellect, sees that he ought to abstain from drinking wine lest the fever increase. But desire prompts him to take things for the sake of what is right now, that is, in the present moment. For it seems that what is pleasant in the present is pleasant simply speaking, and good, because the future is not being considered.

830. Then, at the mover, therefore (433b10), he shows the order of the movements in question; and this, in three stages.

First, he shows how the factors in movement are at once many and one.

Second, at since there are these three (433b13; [831]), he explains how they are ordered to each other.

Third, at now, in summary (433b21; [321]), he briefly defines each of the factors on which movement depends.

First, then, he observes that if the movers are considered formally and according to their species, they will be one mover—namely, the object of appetite, or the appetite itself; for among all of them, the object of appetite is the first mover, for this is the unmoved mover, insofar as it is understood or imagined. (For it is manifest that the secondary movers do not cause motion except insofar as they share in the first, so they all as such come together in the species of the first mover.) And yet, though all the movers are one according to the species of the first mover, still numerically there are many.

831. Then, at since there are these three (433b13), he assigns the order of motion, and he interrelates three things found in movement: one is the mover, next is the organ by which it moves, and third is that which is moved.

The mover is twofold: an immobile mover, and another that moves through being moved itself. In the case of animals, then, the unmoved mover is some good in action, which moves the appetite insofar as it is understood or imagined.

The mover that is moved is the appetite itself, for everything that desires is moved insofar as it desires, and the appetite itself is a certain act or movement, insofar as motion is the act of what is perfect, as was said above about the activity of sensing and understanding.

What is moved is the animal itself.

And the organ by which the appetite moves is a bodily part, that which is the primary organ of movement; hence it must be studied along with the activities common to body and soul and is, in fact, examined in the Movement of Animals. (Aristotle, Movement of Animals, 698a1–704b3.) But in this book, he intends to determine about the soul in itself.

832. Next, at now, in summary (433b21), he briefly states his view on the organ of local motion. He says, in summary, that the primary organic mover must be such that the principle and end of the movement are in the same thing, as if in a certain circulation, in which there is the convex and the concave, of which one is as the end and the other is as the beginning. For the concave is as its end, but the convex seems to be like the beginning of motion; for it is according to the concavity that it is contracted into itself, while according to its convexity, there is expansion, as from itself there is a beginning of motion and a pushing.

833. Now, the starting point and end of the movement are in this, but the principle in every motion whatsoever must be immobile; for example, while the hand is moving, the arm is at rest, and while the arm moves, the shoulder is at rest—as all movement must proceed from something immobile.

Therefore in that first organ of motion, which is the heart, there must be something at rest inasmuch as it is a principle of motion, and something else that is moved inasmuch as motion is terminated in it. However, these two things in the organ, the resting and the moved, though distinct in account, are in the subject and in magnitude inseparable from each other.

834. And that the organ must be both starting point and end (and therefore both resting and mobile) is clear from the fact that all animal movement is composed of pushing and pulling. In pushing, what is the mover is only the starting point of the motion, since the impelling agent thrusts from itself what is impelled. But in pulling, what is the mover is the term of the motion, for what is pulled it pulls to itself. Thus the first organ of local motion in animals must be at once both a starting point and a term.

835. So there must be in it something that stays still and yet thereby initiates motion. And in this it resembles circular movement: for a body revolving in a circle does not as a whole change place (except maybe in account), on account of the immobility of the center and the poles. As a whole it remains in the same place in subject, but its parts are changing their places in subject, and not only in account. And so it is with the motion of the heart: it remains fixed in the same part of the body, while it dilates and contracts and so gives rise to movements of pushing and pulling. Thus it is, in a sense, both resting and moving.