Commentaria in Summam contra Gentiles, Liber I

Having set aside those considerations by which the inquiry into whether God exists was thought to be vain, Saint Thomas adduces the arguments of philosophers as well as theologians by which it is proved that God exists ¹. In this matter he does two things principally: first, he introduces the arguments taken from Book VIII of the Physics; second, the arguments taken from the Metaphysics and from Damascene ². As to the first, he does two things: first, he introduces those arguments themselves; second, he shows how much force they have ³.

I. As to the first, it is argued first ⁴ thus: Whatever is moved is moved by another. That mover, then, either is itself moved or is not. If the latter, the point is established: for we call God an unmoved mover. — If the former, then it is moved by another mover. But there cannot be an infinite regress. Therefore it is necessary to posit some first mover that is unmoved.

2. The first assumption is proved. First: what is moved by itself is moved first. Therefore, upon the rest of one part there follows the rest of the whole; for if, while one part is at rest, another part of it were being moved, then the whole itself would not be moved first. But that whose rest follows upon the rest of another must have its motion follow upon the motion of the other. Therefore such a thing is not moved by itself. Therefore what was posited as being moved by itself is not moved by itself. — Nor does it stand in the way if it be said that a part of a self-mover cannot be at rest; likewise, that it does not belong to a part to rest or be moved except per accidens, as Avicenna objects. For the force of the argument consists in this: if something moves itself first, its being moved does not depend on anything else. But the being moved of something divisible depends on its parts, just as its esse does. Now this conditional must be true: If a part were at rest, the whole would be at rest. And this can be true even with the antecedent being impossible.

Second, it is proved by induction, by running through all things that are moved either per se, or per accidens, or by violence, or by nature.

Third, because everything that is moved, insofar as it is such, is in potency; and everything that moves, insofar as it is such, is in act. But the same thing cannot be simultaneously in act and in potency with respect to the same thing.

Saint Thomas adds, moreover, that there is no difference between Plato's position that one must arrive at a first thing that moves itself and Aristotle's position that one must arrive at a first thing altogether immovable. For Aristotle took motion as it is the act of a being in potency, insofar as it is such; Plato, however, took motion for any operation whatsoever, so that to understand is a kind of being moved.

3. That there is no process to infinity among movers and moved things, which was assumed second in the principal argument, is proved. First because, since all such infinite things must be bodies; and since a body that moves a moved thing is itself moved while it moves; it is necessary that all of them be moved while one is moved. And since one of them is moved in a finite time, because it is finite, it is necessary that all those things be moved in a finite time. But this is impossible: because, since they are as it were one mobile thing by continuity or by contiguity, one infinite thing will be moved in a finite time.

Then, because there will be no first mover, but all things will be as intermediate movers. And thus nothing will be moved: for, when the first mover is removed or ceases from moving, none of the others will move anything, nor will anything be moved.

Then, since all things will move as if instrumentally, and there will be no principal mover, in this way nothing will be moved either.

II. Concerning the first argument by which it is proved that everything moved is moved by another, since it is assumed that, if something moves itself, that thing must be first moved, note that Saint Thomas here speaks according to the mind of Aristotle: namely about what moves itself first, and not about what does not move itself first. For if something moves itself first, the whole must move itself as a whole, and be moved as a whole, so that it may be both first moving and first moved. For if only a part were to move and not the whole, the part would be first moving, that is, not through anything else; but the whole would not be said to move first, but through another, that is, through the part. Similarly, if only a part were moved of itself, that part would be first moved, while the whole would be said to be moved not first, but through the part.

III. Concerning that proposition, "That which is at rest while another is at rest is not moved by itself," a doubt arises. For someone might say that it is true of what is at rest with respect to the rest of another mover, but not of what is at rest with respect to the rest of a part. For the part is the matter of the whole, but not that which moves the whole. Therefore, that the whole is at rest when a part is at rest does not show that it is moved by another; rather, that the motion of the whole cannot exist without the motions of its parts, just as nothing can exist without its own matter. And this presents no difficulty.

To make this evident, it must be premised, according to the Commentator, Physics VII, commentary 2, that the proposition is to be understood of what rests per se with respect to another's rest, and not of what rests per accidens. For if a stone were supposed to descend by itself, it could nevertheless come to rest upward at the rest of a millstone meeting it and violently held back; but this would be per accidens. — To the doubt it is said that something is argued not to be moved first by itself not only if it rests at the rest of a mover, but also if it rests at the rest of a part. For, as Albert says, Physics VII ⁵, if something is supposed to move itself first, then while one part of it rests, the remaining part could be moved by the motion of the whole: otherwise moving and being moved would not belong to the whole as first. Therefore, if while a part rests the whole rests, this argues that the whole is moved by another.

IV. But what St. Thomas further assumes, that the being moved of a divisible thing depends on its parts just as its esse does, presents a difficulty. For it seems rather to be the other way around. For esse and motion do not belong first and per se to the parts, but to the whole: since the parts exist only through the esse of the whole, nor are they moved except by the motion of the whole, if what is locally moved is a continuum. Therefore the esse and motion of the whole do not depend on the esse and motion of the parts, but rather the esse and motion of the parts on the esse and motion of the whole.

It is answered that, although the parts are formally through the esse of the whole, and likewise are formally moved by one motion, which is the motion of the whole continuum, insofar as motion is divided according to the division of the mobile thing; nevertheless they are the cause of the whole in the genus of material cause, and the motions of the parts are the matter of the motion of the whole. And thus the parts, as such, are prior to the whole. Hence the esse and the motion of the whole depend on the parts by way of generation and in the genus of material cause; but the parts depend on the whole in the genus of formal cause.

2. But then a greater doubt arises. If nothing moves itself in the first place precisely because its being moved depends, in the genus of material cause, on the being moved of its parts, it follows that neither could anything be moved by another in the first place: for in every moved thing it is true that the being moved of the whole depends materially on the being moved of the parts.

It is said first that, although something may be moved first by priority of time and priority of information, because something whole is moved and informed all at once according to all its parts by the motion; nevertheless it is true that nothing is moved first, even by another, by priority of causality of every kind—that is, in such a way that its being moved would not depend on the moving of another in any genus of cause. For just as the whole depends materially on the parts, such that when the parts are removed the whole is removed; so the motion of the whole depends on the motions of the parts, such that when the motions of the parts are removed, the motion of the whole is removed.

It is said second that, if something moves itself first in such a way that the whole moves the whole according as it is itself, and the whole according as it is itself is moved, it must be that the whole is moved by itself with a priority of causality, such that in no genus of causality does the motion of the whole depend on another; and likewise that the motion of a part being removed does not remove it from the whole. For as is clear from I Posterior Analytics ⁶, what belongs to something first does not belong to it through another, but rather other things through it; nor is it removed from it because it is removed from another; as we showed against Scotus in VII Physics ⁷; for there we treated this matter more diffusely. And since it is impossible that the motion of anything not depend on the motions of its parts, therefore it is also impossible for something to move itself first.

V. Further, in the second argument, by which it is proved that nothing is moved by itself through induction, note that what is moved per accidens can indeed in some way be moved by itself, namely when something moves another thing and is moved with respect to that thing's motion, as when the soul is moved to the motion of the body moved by itself, and the sailor to the motion of the ship; but it cannot be moved by itself first. For if it is moved with respect to the motion of another, it is manifestly clear that it is not moved first and in virtue of itself.

VI. Concerning the third argument for the same position, a doubt is raised on the authority of Scotus, I Sent., d. III, q. 7, ad argg. pro 2ª opin. For he says that, although nothing can be at once in formal act and in formal potency with respect to the same thing—for instance, actually hot and potentially hot—nevertheless something can be at once in virtual act and in formal potency. And thus he holds that something can move itself first while it is in virtual act, namely because it has the power by which it is able to move; and while it is in formal potency, namely because it does not have formally the form which it acquires through motion, but is able to have it. This he explains more fully in II, d. II, q. 10, ad 2.

He adds also that this proposition, Nothing acts upon itself, is not true except of some univocal agent. — Indeed, when he proves the proposition itself by the argument adduced, he infers that the same thing would be hot and not hot; likewise, moreover each and every one of the others, whatever moves, must have something univocal. In these words he plainly seems to mean that only in the case of univocal things does he hold it true that nothing moves itself primarily, but not in the case of equivocal things.

VII. But against this reply an argument is brought. And first, that the first point is not Aristotle's meaning is argued thus. From the proposition proved, namely that the same thing does not move itself first, Aristotle wishes to establish that the self-mover is divided into two parts, one of which moves and the other is moved. Hence at the end of the text he concludes: This therefore moves, and that is moved, of the thing that moves itself. But if the assumed proposition, namely that the same thing cannot be in act and in potency at the same time, were understood only of formal act and formal potency, and not of virtual act and formal potency, the intended conclusion would not be proved. For it would be said that a self-mover locally is not in formal act but in virtual act and formal potency; and thus it need not be divided into two parts, since being in virtual act and in formal potency can belong to the same thing at once; and consequently the same thing can move itself first. Therefore.

Furthermore, something is said to be according to its nature in virtual act of some form because it has the power of producing that form. But what has the power of producing some form in itself cannot lack that form. Therefore something cannot at the same time be in virtual act and in formal potency with respect to that form: — The minor is proved. Because, once a sufficient natural cause is posited, its effect is posited in reality.

2. That what has been said is not true is proved. And first, that it is not Aristotle's meaning. For since the Philosopher, from the fact that there is no process to infinity, deduces that one must arrive at a first self-mover, and that one part of it must be moving and another moved—because nothing moves itself first—he either posits the heaven as mover in the manner of a univocal agent or in the manner of an equivocal agent. Not as a univocal agent: both because Aristotle holds that that by which it moves is immobile, and consequently the heaven, insofar as it moves itself, does not move itself through motion, so as to be a univocal mover; and because a thing moving itself locally does not cause in itself motion through local motion existing in itself, as though local motion were the form by which it acts. Therefore it moves itself as an equivocal mover. Therefore the proposition assumed is not true only of univocal agents; but also in equivocal agents, according to Aristotle, the self-mover must be divided into a moving part and a moved part.

Second. An equivocal agent is said to be one to which it does not belong to have in itself the form of its effect, but something more eminent in which that form is contained. But if something existing in virtual act were at the same time, according to the same respect, in formal potency, it would at some time have in itself formally that form of which it was the cause—namely, when it had been reduced from potency to act. Therefore such a thing would not be an equivocal agent.

Third, the reason why it is repugnant for something to be at once in formal act and in formal potency is that the ratio of act and the ratio of passive potency are opposed, since the ratio of the one consists in perfection, while that of the other consists in imperfection and privation. But virtual act is of no lesser perfection than formal act; indeed, it possesses a more excellent mode. Therefore, if it is repugnant for something to be at once in formal act and in formal potency—in those things, namely, that are said univocally—it will be much more repugnant for something to be at once in virtual act and in formal potency, namely in things that are equivocal.

But as for the authority of Aristotle, setting aside the exposition of the Commentator on that passage, it is said that Aristotle makes mention of univocals because in them it is manifest to us that the same thing cannot be in act and in potency; leaving it as evident that if this cannot be so in those cases, much less can it be so in equivocals, in which act is of a more eminent mode.

VIII. But a doubt remains concerning this from the words of St. Thomas in the First Part, q. 77, a. 6. For there he says that the subject, insofar as it is in potency, is receptive of its proper accident, but insofar as it is in act, it is productive of it, from which he concludes that it is not unfitting for the powers of the soul to flow from the essence of the soul as from a principle, and yet for some of them to be in the soul alone as in a subject. For from these words the argument is drawn as follows. The soul is in virtual act with respect to its powers, and in formal potency with respect to the same: since it is productive of them insofar as it is in act, and receptive of them insofar as it is in potency. Therefore.

It is answered that from the words of Saint Thomas it does not follow that the soul is in virtual act and in formal potency, but only that it has something of actuality and something of potentiality: by the one it produces, while by the other it is the subject of the powers. For to be in formal potency is not to have a form and to be able to have it; and thus to be in virtual act and in formal potency is to be able, through a mediating action and transmutation, to produce in oneself and receive a form which one does not have. But this is not found in the soul with respect to its powers: for the soul never lacks its powers, especially those which are in the soul alone, such as the intellective powers, but is always conjoined with them; since they are not produced through a mediating action, but through natural sequel. Nor is it unfitting that the same thing cause something in itself through natural resultation, and be the principle of that thing insofar as it has something of actuality, while being the subject insofar as it is not simple act but has something of potentiality: just as the soul, in relation to its esse, has the character of potency. But it is indeed impossible that something cause in itself some form through a mediating action and transmutation: for this supposes that a thing be at once in act and in potency remote from act.

It must be noted, however, that when we say that the same thing cannot be mover and moved, agent and patient, with respect to the same thing, we do not mean identity of supposit: for the same supposit can be both agent and patient. Rather, we speak of the identity of the formal principle of acting and of being acted upon: for we say that one and the same thing cannot be the principle of acting and of being acted upon with respect to the same thing.

IX. Concerning the first argument by which it is proved that there is no process to infinity among movers and moved things, a doubt is raised. For it seems ineffective. It does not follow, namely, that if one continuum is made out of an infinite number of movable things, then one motion, numerically infinite, occurs in a finite time—speaking of infinite motion in the sense in which the whole infinite body traverses some space, in which sense it is proved in Physics VI that an infinite mobile cannot be moved in a finite time. For it would be said that if there are infinitely many movers and moved things, separate and distinct, all of them will be moved in the same finite time, but not by traversing one and the same finite magnitude, but one after another. For each will traverse as much magnitude as the last of them moves through in so much time; and the mover next to it, equal to it, will traverse an equal magnitude in the same time, if the mover applied to the moved thing moves it with rectilinear motion, and is of the same quantity as it, and is applied at its extremity—as if a rod of one cubit were pushing a rod of the same quantity. In the same way, even if we were to imagine that from these things one continuum were made, it would not follow that the whole of it traverses one magnitude in a finite time; rather, its parts, finite in quantity, would traverse magnitudes diverse and finite in quantity but infinite in number, in a finite time, such that each finite part of it would traverse some finite space. And although this is indeed impossible, since Aristotle proves it in Physics III⁸and I Caeli⁹, that the infinite cannot be moved; nevertheless this does not seem to be what Aristotle intends here, since in Physics VI he did not have this sense when he proved that the infinite cannot be moved in a finite time.

I would say, saving the judgment of a better authority, that this argument of Aristotle holds only in circular motion, whereby one circular body is moved circularly by another containing it, so that all are moved by the same diurnal motion, as happens in the celestial spheres. For Aristotle considered the order of the universe, in which the elements are contained by the sphere of the moon, and the celestial bodies contain one another, and all are moved each day from east to west, returning to the east, so that in equal time both lower and higher bodies are moved by such a motion: in these bodies, since they have an essential order in moving, he proved that there is no regress to infinity. And it follows well that, if from infinitely many bodies so moved one continuous body were made, an infinite body would be moved through some space in finite time. For since all spheres now traverse the space from east to west, returning to the east, in a natural day—notwithstanding that one is greater than another, and the higher sphere traverses a greater space—if there were an eleventh sphere, it would traverse its space in the same time; similarly if a twelfth, if a thirteenth, and so on to infinity; on that supposition that, if all things are movers because they are moved, it is necessary that all be moved simultaneously. It follows therefore that those infinite bodies would traverse some space in finite time by their revolution. If therefore we imagine that from those infinitely many bodies one infinite body is made, then that body will traverse some space in finite time: which is disproved in Physics VI.

X. Concerning the second argument for the same conclusion, a doubt is raised. For those who posit an infinite process among movers and moved things would deny that assumption, namely, that when the first mover is removed or ceases from moving, none of the others would be moved. For where there is no first, the posterior cause does not depend on the first in causing, nor does the complement of causality have dependence on the first. For although an infinite ascent and descent with temporal succession repugns the complement, nevertheless an infinite ascent and descent of causality does not repugn the complement. Such is the infinity of infinite movers and moved things: because it is supposed that all move and are moved simultaneously.

It is answered that Aristotle's argument is effective if it is well considered. For the foundation of the argument is that among movers and moved things ordered essentially, there must be some first. This is evident to one who considers it diligently. Because if there were many movers and moved things in which there were no first unmoved thing, the whole multitude of movers would stand as one moved mover. But this is impossible: for then something would be moved and be moved by nothing. For that multitude would not be moved first by itself: since nothing moves itself first. Nor because one unmoved part would move the other parts: since no unmoved mover is posited there. Nor because one moved part would move another: since the aggregate of them has the character of what is moved, and thus it would need something else by which it is moved.

If it is said that the whole multitude of movers and moved things need not be related as one mover moved by another extrinsically, but that their condition is preserved because one is moved by another, and that by another, and so on to infinity—just as in an infinite multitude of numbers each number is both exceeding and exceeded, yet the whole multitude need not be exceeded by anything—the reply is that every mover must be in act, and likewise everything locally moved. Therefore the whole multitude of movers and moved things can be taken as one: especially since none of them has what moves except insofar as it is moved; and if it has the character of something moved, it must be moved by something. But an infinite multitude of numbers is posited not in act but in potency. Therefore it is not necessary that the whole multitude be exceeded by anything.

Since, therefore, among things essentially ordered there must be some first; and in an infinite series there is no first; it follows that there cannot be infinitely many things essentially ordered. — On these matters see Capreolus, I Sent., d. III, q. 1.

XI. The second principal argument is as follows. If every mover is moved, then this proposition is either true per se or per accidens. If per accidens, then it is not necessary. Therefore it is contingent that no mover is moved. Therefore it is contingent that nothing is moved: because, if a mover is not moved, it does not move, as the opponent says. But Aristotle holds this to be impossible. Therefore, and so on.

Item, if a mover and a moved thing are joined in something per accidens, it is probable that the mover can be found without that by which it is moved, since the moved thing is found without that which moves it. For if any two things are joined per accidens in something, and one of them is found without the other, it is probable that the other can be found without it. Nor does this stand in the way of two things of which one depends on the other but not conversely, as with substance and accident; for these are joined per se, not per accidens¹⁰.

But if it is true per se, then either the mover is moved in the same species of motion by which it moves, or in another. If in the same, then it follows that the thing altering is itself altered, and the teacher taught according to the same science, which is impossible. — If in another, since the genera and species of motion are finite, there will be no regress to infinity: and thus there will be a first mover not moved by another. Unless perhaps it is said that a reflection occurs through a return to the first. But from this it would follow that the mover, with respect to some species of motion, is moved with respect to the same species, not immediately but mediately.

2. Concerning that proposition, If any two things are joined per accidens in something, and one of them is found without the other, it is probable that the other can be found without the first, it should be known, according to the Commentator, Physics VIII, comment 37, that it is to be understood of those things each of which exists per se, that is, of which neither is necessary for the esse of the other. For if one needs the other for its esse, that which needs the other cannot be separated from it: just as, although some form is found without matter, matter nevertheless cannot be found without form; and although some substance may be without an accident, an accident nevertheless cannot be without substance; because both matter needs form for its esse, and accident substance. Therefore, in those things alone does it happen that one is found per se if the other is found without it, which are joined wholly per accidens, namely such that neither needs the other for its esse.

It should also be noted that the possibility of which we speak here is logical, not natural. For perhaps no species can be separated from inseparable accidents by a natural power, as a swan from whiteness; yet it is not repugnant for a swan not to be white. Hence what the Commentator says, that in such cases it is necessary that one be without the other, must be understood as referring the necessity to logical possibility, so that the sense is: It is necessary that each be separable, that is, that it be able to exist without repugnance. For Albertus ¹¹ and Saint Thomas ¹² say that this is probable, but not necessary. This is also what the text of Saint Thomas has. For which reason the Commentator himself, in Metaphysics XII, commentary 35, stating the same proposition, says that everything composed of two things, one of which can exist per se, will make it possible for the other also to exist per se, unless the composition is of substance and accident.

3. This is also what Saint Thomas says, namely that substance and accident are not joined per accidens but per se (although in some corrupted books the contrary is found ¹³); this must be understood with their common rationes considered, and not of this or that substance and of this or that accident according to their proper rationes. For a wall and whiteness, if considered particularly, are joined per accidens; but if the wall is considered as it is a substance, and whiteness as it is an accident, then they are joined per se and not at all per accidens, because substance is included in the ratio of the accident, and among the philosophers it is repugnant for an accident to be in the nature of things without a subject.

XII. As to the second point ¹⁴, because arguments of this kind do not lead to the very esse of God, but only to the conclusion that there is some first mover that is not moved by another, Saint Thomas shows that Aristotle is thereby led on further to seek that God exists. For he argues as follows. One arrives at a first mover not moved by any exterior other. Therefore either that mover is altogether immobile, or it is moved by itself. If the first, the point is established. If the second — which is plausible, since what is through itself is prior to what is through another — it cannot be said that the whole is moved by the whole: for the aforementioned absurdities would follow. Therefore one part of it is only moving, while the other is moved. And thus it is likewise established that there is something moving and immobile. Nor can it be said that both parts are moved, one by the other; or that one moves itself and the other; or that the whole moves the part, or the part the whole: for the same absurdities would follow. Therefore, and so on.

2. If it were said that in the first self-mover the moving part is moved per accidens, as in animals, an argument is brought against this. First, because animals, since they are corruptible, have their moving part moved per accidens. But corruptible movers must be reduced to some eternal mover: for, since motion is eternal, according to Aristotle, the generation of corruptible self-movers must be eternal. Now no one of these can be the cause of this perpetuity, because it does not exist always; nor all of them together, because they are infinite, and moreover they do not exist together. Therefore there must be something that moves itself eternally.

Second, because no self-mover is moved always whose mover is moved per se or per accidens. But the first self-mover is moved always: otherwise motion could not be eternal. — Nor does it stand in the way that the movers of the lower spheres are moved per accidens, since this is only by reason of their mobiles following the motion of the higher sphere.

3. Saint Thomas adds, moreover, that because God is not a part of anything that moves itself, he further investigates from this another mover entirely separate, which is God, on the ground that what moves itself is moved on account of the appetite for some desirable object, which is superior to it in moving.

XIII. If it is said, first, that the said arguments proceed from the supposition that motion is eternal, which is false — he replies that the most effective way of proving that God exists is from the supposition that the world is new; not so, however, from the supposition that it is eternal ¹⁵. For if the world began anew, it is plain that some cause producing it anew must be posited. But under the supposition that the world is eternal, this seems less evident.

2. If it is said, second, that the heaven seems to be assumed to be animate, since it is posited as moving of itself; but this is not granted by many: — the answer is that if the first mover is not posited as moved of itself, it must be moved immediately by that which is altogether immobile. For this reason Aristotle introduced one or the other under a disjunction.

XIV. Note, regarding that proposition—"Since animals are corruptible, the moving part in them is moved per accidens"—that the phrase "since they are corruptible" is not taken as the cause of the fact that the moving part in them is moved per accidens, but rather to express the condition of animals within the order of things that move themselves. For these things fall into two classes: namely, some self-movers are corruptible, while others are incorruptible. In corruptible things the moving part is moved per accidens, because when the body is moved from place to place, everything that is in the body is moved; but in incorruptible things, which are moved with an everlasting motion, the moving part is not moved. Animals, therefore, which exist among us belong to the class of self-movers that are corruptible. Hence in them the moving part is moved per accidens.

But although the corruptibility of that thing is not its cause, both nevertheless proceed from the same cause, as the Commentator seems to hold, Physics VIII, comm. 52, namely both that it is corruptible and that the moving part is moved per accidens: from this, I say, that the moving part is established in its esse through its union with the moved part, and is connected to it variably; whence it follows that, where one is posited, the other must also be posited; because, once one is posited, its cause must be posited; and once that is posited, the other effect must necessarily be posited as well.

XV. Concerning that proposition, that no self-mover is always moved, since its mover is moved per se or per accidens, it must be noted that a twofold accidental character of the motion of the moving part is found in animals: one from without, insofar as an animal is aroused by something to move itself; for when the body is altered and aroused to motion, the soul is aroused and moved per accidens. The other is from within, namely from the moving part itself, when, in moving the body, it moves itself per accidens. But since what is per accidens can happen to be removed, therefore in them the motion can cease, the moving part ceasing. And consequently the whole will not be moved always.

XVI. As to the movers of the orbs, how they are said to be moved per accidens not on account of themselves but on account of the bodies moved by them: it must be noted that, since to be moved per accidens is to be moved by the motion of another, this can happen in two ways: either because the thing itself is changed from place to place, though this belongs to it by reason of the motion of another, and this is called being moved per accidens on account of itself; or because the thing itself does indeed not change place through the motion of another, but something to which it is joined. In the first way, therefore, the movers of the lower orbs are not moved per accidens; but in the second way, namely because the orbs moved by them are moved by the motion of the higher sphere, not by their own mover, but per accidens.

2. But how they are not moved per accidens by reason of themselves: it must be considered, as Saint Thomas says in Iª, q. LI, a. 3, ad 3, and I Sent., d. XXXVII, q. 4, a. 1, ad 4, and II Sent., d. VIII, a. 4, ad 4, in answer to the question raised, that nothing is moved per accidens when that in which it is is moved, unless it is definitively in it in such a way that it is not in another; but it is indeed moved per accidens when that in which it is definitively is moved: just as the soul is not moved when the hand is moved, but is indeed moved when the whole body is moved. It must be noted, however, as he intimates in the First Part and in II Sent., that that in which the mover is definitively either changes the place in which it is with respect to itself as a whole; or it always remains really in the same place, although its parts change place, as happens in circular motion. If, therefore, something indivisible is united to a body as a mover but in the whole, as the soul is to the body, and that body is transmuted from place to place, it is necessary that the indivisible also be changed per accidens: because it too changes the place proper to it by reason of the body. But if it is not changed from place to place, that indivisible is not moved even per accidens: because it is united to the body as a whole, and that whole does not change place. But if it were affixed to some determinate part of that body, then it would be moved per accidens: because that part would be changed from place to place.

According, therefore, to the various opinions concerning the movers of the heavenly bodies, motion per accidens can be attributed to them in different ways. For if we suppose the mover to be present to the orb as a potter is present to his wheel, so that by its power it always touches one part after another of the mobile thing that succeeds in the east, it is clear that it need not itself be rotated with the motion of the orb, just as neither is the potter rotated with the motion of the wheel. — But if we suppose it united to some determinate part of the orb, it will have to be rotated just as that part to which it is attached is rotated. — Yet if we suppose it united to the orb as a whole, as the intellectual soul is united to the body, then it is not moved even per accidens, as Saint Thomas holds in the places cited above: since the whole does not change place really, but only according to reason. — Whether, however, it is united to the orb according to esse will be shown below ¹⁶.

XVII. Further it must be known that, because Saint Thomas says that Aristotle investigated in the Metaphysics from the mover which is a part of the self-mover another mover entirely separate from matter, Aristotle posited two orders of immaterial substances: as Saint Thomas himself seems to intend, XII Metaph., expounding text 48 ¹⁷; but more explicitly in the Questions on Spiritual Creatures, art. 6, body of the article and reply to the tenth objection, and also in the Treatise on the Angels ¹⁸ teaching. For there are certain substances in him which are movers of the heavenly spheres, which are also called the souls of the heavens; and others which are the proximate ends of those motions. But all these orders are contained under God, as under the first separate substance. Thus therefore Aristotle, after he investigated the mover of the heaven, which is its soul and a part of the self-mover, investigates from this one another mover which is not a part of the self-mover but is separate from all matter: by this, I say, because a part of the self-mover moves on account of an appetite for something superior in moving, namely so that it may be assimilated to it, and may fulfill in effect what is contained virtually in the first mover.

XVIII. It must be noted, however, that in the response to the first objection which St. Thomas raises there are some corrupt texts ¹⁹. For where it is said that the most efficacious way of proving that God exists is from the supposition of the eternity of the world, since with this supposition it seems less evident that God exists, it should be read thus, as the corrected manuscripts have: It must be said that the most efficacious way of proving that God exists is from the supposition of the newness of the world; but not so from the supposition of the eternity of the world, since with this supposition it seems less evident, etc. In these words it is made clear that an argument taken from the eternity of the world is indeed efficacious for proving that God exists, but the argument taken from the newness of the world is more efficacious and more manifest.

Concerning the reply to the second objection, it must be noted that the sense of the reply is that Aristotle's argument is not impeded by the fact that many do not grant that the heaven is animated: for if they deny the first point, that what moves is not moved by itself and is not animated, they must grant that it is altogether immobile, and thus they grant that God exists. And therefore Aristotle introduced one or the other of these under a disjunction: namely, that the mover which is not moved from without must either be moved by itself, or be altogether immobile; because, whether one or the other be granted, it follows of necessity that one must arrive at something altogether immobile, which is God.

XIX. But two doubts arise here. First, because the conditions which Aristotle attributes to the separate mover in XII Metaphysics ²⁰, such as having infinite power of esse, being immaterial, etc., he attributes in VIII Physics ²¹ to that first mover whom he there investigates through motion. Therefore that mover investigated in the Metaphysics is not other than the one investigated in the Physics.

It is confirmed by the words of Saint Thomas on Book XII of the Metaphysics ²², and of Aristotle, in the inquiry that concerning the very substance about which he determines in Book XII of the Metaphysics, that it moves as the end desired and loved, it has been shown, namely in Book VIII of the Physics, that it has no magnitude: and he takes up the same argument again.

The second is ²³, because it does not seem necessary that, if the mover of the heavens is appetitive and intelligent, it should move on account of an appetite for some end distinct from itself. For it can move for its own sake as for an end: just as God acts for His own sake. And thus it will not be necessary to posit another mover higher than the soul of the heavens.

XX. To the first objection it must be said that the ancient philosophers, against whom Aristotle argued in the Physics, considered only the motion of bodies. Hence whatever was said among them to be moved was understood to be moved by some motion of those by which bodies are moved. Therefore, if something is shown to be wholly immobile with respect to such motion, so that it is moved neither per se nor per accidens, that thing must be God according to them: for by the name of God we understand the first mover wholly immobile. Since, then, in Book VIII of the Physics Aristotle demonstrated that one must arrive at something that is moved neither per se nor per accidens by the motion of bodies—although that mover there investigated is a part of the self-mover, and is not the first mover simply—he nevertheless spoke of it there as of a first mover simply immobile, and attributed to it the conditions of the first mover simply, as the opinion of the ancients required. But because besides the motion of bodies there is another motion that belongs also to immaterial things, insofar as they are moved by the intelligible and the desirable, therefore for something to be simply immobile it is necessary that it not be moved by this spiritual motion either. On this account Aristotle in Book XII of the Metaphysics, having proved in the Physics that there is some mover of bodies that is immobile with respect to their motion, investigates another mover, by which that immobile mover, which is a part of the self-mover, is moved as by a desirable and intelligible object; but that mover is himself wholly immobile, being desired by others, while he himself is moved by no desirable or intelligible object.

To the doubt, then, it is said that the mover investigated in Book VIII of the Physics is indeed other than the one investigated in Book XII of the Metaphysics. That he attributes to it certain conditions of the first mover simply speaking is because he there used it as the first mover simply speaking, alluding to the opinion of the ancient philosophers, as we have said.

By the same token the confirmation is clear. For they say they proved it of the same substance, because Aristotle used the same word there, adapting the truth of the philosophers to the opinion.

2. For the clarification of the second point ²⁴, it must be noted that in Aristotle the first intelligence, which is God, differs from the other intelligences, because the first has the character of a first and principal cause, while the others have the character of a secondary cause and instrument. For it is necessary to arrive at one first among movers which is the cause of the others, as is proved in Book II of the Metaphysics ²⁵ Now an instrument works so that what is contained virtually in the principal agent may be unfolded in the effect. Therefore the intelligences other than the first cannot act for their own sakes as for the ultimate end, since they have the character of an instrument and of a secondary agent. Nor is it sufficient that each act for its own proximate and proportionate end: since the action of all must be reduced to one common end, beyond particular ends; just as there is also one first and universal principle moving all things.

To the doubt, therefore, it is answered that the second intelligence cannot act for its own sake as for its ultimate end, although the first can do so, for the reasons given.

XXI. As to the second principal point ²⁶, Saint Thomas adduces arguments from the Metaphysics. The first of these, Metaphysics II, text 6, is as follows. Among efficient causes one does not proceed to infinity. Therefore one must arrive at a single first cause, which we call God.

The antecedent is proved. If one proceeds to infinity, none of the causes will be first. Therefore all the others will be removed, namely those that are intermediate. This is false. Therefore, and so on. — The consequence is proved. Because among efficient causes ordered in a series, the first is the cause of the intermediate, and the intermediate is the cause of the last. But when the cause is removed, that of which it is the cause is removed.

XXII. The second argument is this. There is something maximally true. Therefore there is also something maximally a being. And this we call God.

The consequence is evident from Metaphysics II, text 4, where it is stated that the most true things are the most beings. — The antecedent, however, is shown in Metaphysics IV, text 18, from the fact that we see that of two false things one is more false than the other. Hence it must be that the one is also truer than the other. This is according to approximation to that which is most true.

2. For the clarification of this argument, it must be considered, as Saint Thomas teaches in I, q. 49, a. 3, ad 3, and I-II, q. 22, a. 2, ad 1, that more and less are found in one way in things pertaining to perfection, and in another way in those that import defect. For in things that are called perfections, more and less, or intensification and remission, are attended to by comparison with and approach, greater or lesser, to some highest instance: thus that is said to be more luminous which more closely approaches the supremely luminous, and less luminous which approaches it less. In privation, however, and in defect, more and less are attended to by recession from the highest and perfect thing, since privation is a kind of removal. Therefore, when Saint Thomas had drawn from Metaphysics IV that of two false things one is more false than the other, he did not conclude that this happens by approach to something supremely false, since the false consists in privation; but he ingeniously added that for this reason one must be truer than the other, and hence that there must be some truest thing, by approach to which something is said to be truer or less true, and by recession from which something is more false than another.

3. It must also be noted that, since there are many properties that belong to God alone, sometimes several of His properties at once are explained by some under the name of God as its reason, sometimes one, and sometimes another. Since, then, being the cause of the esse of all beings belongs to God alone, as does likewise the highest and most perfect esse of beings, Aristotle, in Metaphysics II, because among the philosophers the first cause of all things was understood by the name of God, concludes that there must be one first cause of all things, from the fact that there must be something which is being in the highest degree, and consequently that God must exist. St. Thomas, however, seeing that to be being in the highest degree also belongs to God alone, when he has proved this, proceeds no further, since with that single conclusion it stands proved that God exists. — Or else, aiming at brevity, when he has deduced that there must be something which is being in the highest degree, he omits, as known from metaphysics, the conclusion drawn by Aristotle, namely, that there must necessarily be something which is the cause of all things: since what is such in the highest degree is the cause of all other things.

XXIII. But about what has been said there is doubt in two ways. First, it does not seem true that one thing is truer than another. For truth is a kind of adequation, and consequently a kind of equality. But equality does not admit of more and less. — Nor does this inference hold: "One thing is said to be falser than another; therefore also truer." For falsity consists in an inequation and a falling away from equality; but a thing can stand at a distance from the mean in many ways.

Second, the true proposition of Aristotle does not seem to have been assumed by Aureol as the foundation of his argument ²⁷, a proposition which St. Thomas nevertheless leaves unmentioned, namely, that what is most such is the cause of the others. For whiteness is the most perfect thing in the genus of colors, and yet it is not the productive cause of the other colors, as is evident in itself.

XXIV. To the first it is said that truth, insofar as it is in a thing, is founded on the esse of the thing. Hence the material element of truth is indeed the esse of the thing, while its formal element is the adequation to the intellect. We can therefore speak of the truth of a thing in two ways. First, with respect to the material element alone, namely with respect to esse. And thus it is not unfitting that one thing be truer than another, just as one being is more perfect than another. This is why the most perfect of beings are said to be the most true. — Or second, with respect to the formal element, or with respect to the material element as it stands under the formal. And thus one thing is not truer than another. For each thing is naturally apt to adequate an intellect to itself in its own way; and each thing is adequated to the divine intellect according to its own entity; nor can it happen that one is adequated more than another, just as among quantities a piece of wood twenty cubits long is not adequated to a piece of wood twenty cubits long any more than a piece of wood one cubit long is adequated to a piece of wood one cubit long. — The objection therefore proceeds under the second sense. But the words of St. Thomas have the first sense.

To the second, it is said that it is not Aristotle's meaning that the first and nobler species of any genus is the productive cause of the other species of that genus; otherwise man, which is the noblest species of animal, would produce the other species of animal. But rather that where something participates most perfectly in some nature (ratio), so that according to that nature it is said to be maximally such, that thing is the effective cause of all others insofar as they too participate in that same nature. And this is understood in substances: whether the nature according to which they are said to be maximally such be substantial in itself or accidental. For what is maximally hot is the cause of all other hot things, insofar as they are hot. For even if certain things are heated by the light of the sun, or by something else that is not formally hot, they are nevertheless heated by it insofar as it virtually contains fire, which is the hottest of all bodies. — Whiteness, however, is neither a substance nor is it called maximally color, although it is the most perfect species of color: just as neither is man called maximally animal, since the nature of animal is participated equally by all, although he is the most perfect of animals.

XXV. The final argument, taken from Damascene and from Averroes, Physics II, commentary 75, is as follows. In the world we see things of different natures concurring in one order, always or for the most part. Therefore there exists something by whose providence the world is governed. Therefore, etc.

The first consequence is proved. Because things of this kind cannot come together into an order always or frequently unless by the governance of some one, from which it is granted to all and each that they tend toward a certain end.

But against this Aureol says ²⁸ that it is ineffective. For it would be said, he declares, that these diverse things come together into one order and are ordered to one end by their own forms and natures. Yet the order of the universe of nature need not be due to chance: rather it is per se, since it takes its origin from the quiddities of things.

But since Saint Thomas refutes this response below, in the third book ²⁹, let it be deferred until then.