Commentaria in Summam contra Gentiles, Liber I

After Saint Thomas has excluded from God all composition universally, he now, so that the knowledge may be more evident and certain, wishes to exclude the various compositions in particular ¹. In regard to this he does two things: first, he excludes those compositions by which something is said to be composed from certain things; second, that composition by which something is said to be composed with another, chapter XXVI.

On the first point, he does five things: first, he excludes quantitative composition; second, composition from supposit and nature, chapter XXI; third, composition from esse and essence, chapter XXII; fourth, composition from subject and accident, chapter XXIII; fifth, composition from genus and difference, chapter XXIV.

As to the first, wishing to exclude quantitative composition from God, he sets down this conclusion: God is not a body. Concerning this he does three things: first, he brings forward common arguments for it; second, the arguments of Aristotle ²; third, he refutes the errors of the ancients ³.

I. As to the first, he argues first as follows. Every body is composite, because it is a continuum. God is not composite. Therefore, etc.

Second. God is not in potency. Therefore he is not a body. — The antecedent was proved above. — The consequence is proved: because every body is a continuum. But a continuum is in potency divisible to infinity.

But this argument seems not to conclude. For the power in a continuum for division is not a natural power, as is clear in the heavenly bodies, but a power of non-repugnance. Now it does not seem repugnant to God that there be in Him a power of non-repugnance.

It is answered that the power of non-repugnance is twofold: one kind, which has its foundation in the character of active power; another, which has its foundation in the character of passive power. The first power of non-repugnance it is not unfitting to attribute to God—for instance, that God is in potency to the production of another world—because active power signifies a perfection. But it is indeed unfitting to attribute to God the second power, because passive power, as such, signifies an imperfection. Now the power of non-repugnance to division in the continuous is founded upon the character of passive power. Therefore to attribute this to God is unfitting. For since He is of Himself necessary esse, not only does He not have within Himself a natural potency for undergoing division, but nothing can even be in Him through which, insofar as He has it, He would be in potency in any way whatever to be divided.

Third. Either it is a mathematical body or a natural one. Not the first: because that does not exist of itself, since it is an accident. Nor the second: since every such body is movable, inasmuch as nature is the principle of motion ⁴; but God is immovable. Therefore it is not a body.

Fourth. Then our intellect and thought could think something greater than God. And thus God would not be greater than our intellect. — The consequence is proved. Because something greater can be thought than any finite thing. But every body, whether straight or circular, is finite.

It must be noted that there is no contradiction between what is said here and what was said above, chapter XI: for, as I say, here it is taken as an absurdity that something greater than God can be thought, whereas there it was not so taken. For, as we said in that place ⁵, if it is not granted that there exists in the nature of things something than which nothing greater can be thought, then it is not absurd that something greater than God can be thought: and in this sense Saint Thomas spoke above. But given that such a thing exists in nature, as can be established from what precedes ⁶, that something greater than God can be thought is an absurdity. And from this supposition he proceeds here.

II. Fifth. It follows that God is not the first being. This is false. Therefore, etc. — The consequence is proved. Above all bodies there is something nobler and prior. Therefore, if God is a body, something will be prior to and nobler than him. — The antecedent is proved. According to the order of objects is the order of powers. But intellect is above sense: because intellectual cognition is more certain than sensitive cognition. Therefore, above the sensible there is something intelligible. But every body existing in things is sensible. Therefore, etc.

Concerning that proposition, "Intellective cognition is more certain than sensitive cognition," it must be considered that certainty, if taken properly, as Saint Thomas says in the Third Book, d. xxvi, q. II, a. 4, is the firmness of the adherence of a cognitive power to its knowable object. Now we can compare intellective and sensitive cognition in two ways: in one way, considering each with respect to its proper object; in another way, considering each in its order to sensible substances, which fall both under sense and under intellect. If we speak in the first way, I say first that, all impediments removed, there is no greater certainty on the part of the power in the intellect than in the sensitive power. For just as the intellect is always true concerning what a thing is, so sense is true concerning its proper sensible object. And therefore sense adheres as firmly to its proper sensible as the intellect does to its intelligible. — I say second, that the certainty of intellective cognition is greater than that of sensitive cognition on the part of the objects. Because the object of the intellect, which is what a thing is, is more perfect and less changeable than the object of sense. Therefore, in itself, it is naturally apt to produce greater certainty in the intellect than the sensible, which is changeable in many ways, produces in sense. — I say third. If they are considered absolutely, intellective cognition is still more certain. For sensitive cognition can be impeded from certainty per accidens by many causes: for instance, by indisposition of the organ and of the medium, and also by undue distance or proximity. The intellect, however, although it can be deceived through the intervention of composition, as is said in III de Anima ⁷, nevertheless cannot be impeded by as many causes as sense can.

If they are compared in the second way, intellectual cognition is also more certain. For sense does not penetrate the very substance of a thing, but perceives only its extrinsic accidents. The intellect, however, proceeds to the innermost depths of the thing, from which there arises concerning the thing a greater certainty than from sense perception alone.

Since, therefore, intellectual cognition is more certain than sensitive cognition in several respects, the proposition of St. Thomas is absolutely true, although it admits some exception, as is clear from what was said in the first place.

But a doubt arises. For although the object of the intellect is prior and nobler than the object of the senses, it does not seem to follow that anything is prior to body. For it is said that in sensible body are preserved both the character of the object of sense, namely the sensible accidents, and the character of the object of the intellect, namely the quiddity of substance; and within that very body, that which is the object of the intellect is nobler than that which is the object of sense, just as substance is nobler than accident.

It is answered that the foundation of St. Thomas's reasoning seems to be this: just as the intellect is more certain than sense and wholly raised above sense, so there must be something intelligible in the nature of things wholly raised above sensible things—something, I say, that is neither per se nor per accidens sensible on account of its conjunction with a per se sensible. But the quiddity of a sensible thing, although it is per se perceptible by the intellect alone, nevertheless falls per accidens under sense, as is said in II de Anima ⁸. Therefore above it there must be another intelligible.

III. Sixth. Nothing is nobler than God. Therefore he is not a body. — The consequence is proved. Because, since a living thing is nobler than a non-living body, and life is nobler still than a living thing, inasmuch as a living thing has its nobility above other bodies through life, every body will have something nobler than itself.

It must be noted that by the name of life Saint Thomas in this passage understands the soul, by which the body lives; and he takes body absolutely, as it is a body, that is, as having corporeal esse, and as distinguished from the soul precisely insofar as it is the soul. Therefore this argument proves that God is not a body as distinguished from and opposed to the soul; but not as having life, for in this sense too something is called a body. In this sense it follows that with respect to any body whatsoever, whether living or non-living, there is something prior, namely the soul itself, which is related to the body—taken as prescinding from the soul, whether really or conceptually (for this makes no difference to the point at issue)—as act is related to potency. — But if living body were taken not merely for the part that is vivified by the soul, but for the composite of soul and body, then the soul would not be nobler than the living thing: since a part is not nobler than its whole, indeed is more imperfect.

That which Saint Thomas says, that a living thing is nobler than a non-living body, must be understood simply and absolutely. In a certain respect, however, some non-living body can be nobler than a living one. For since the nobility of a thing is taken from its form, and the soul is by its own nature a nobler form than one giving only corporeal esse to a body, it follows that an animate thing is simply nobler than an inanimate thing. But because it can happen that a nobler form according to substance is more imperfect according to some particular aspect, for instance in respect of how it informs the body, since it informs it in a less noble manner—as Saint Thomas says in the First Part, q. 70, a. 3, ad 2, and in De Potentia, q. 6, a. 6, ad 13, of the intellectual soul, that it is nobler in itself than the form of the heavens if the heavens are inanimate, but not in respect of informing the body, since the latter gives incorruptible esse, whereas the soul gives corruptible esse by comparison with the body—therefore it is not unfitting that a non-living thing be nobler than a living one in some particular respect. Thus we say that a fly is simply nobler than the heavens, but in a certain respect the heavens are nobler than a fly. Nor does it stand in the way that the heavens are its cause: for it is not the principal cause, but the instrument of the moving intelligence.

IV. As to the second ⁹, he sets forth four arguments of the philosophers, by which, from the eternity of motion, they prove that neither is there a body nor a power in a body ¹⁰.

The first argument is this. God is the first mover of the heavens, wholly immobile, both per se and per accidens, since he moves with everlasting motion. Therefore he is not a body, nor a power in a body. — The consequence is proved. Because no body moves unless it is moved, since mover and moved must be together. Likewise no power in a body moves unless it is moved per accidens. — This argument is taken partly from Book VII and partly from Book VIII of the Physics.

To make this argument clear, we must first consider that the proposition "No body moves locally unless it is itself moved" is to be understood here of purely local motion, in which one body is moved by another not through the impression of some form that would be the formal principle of the motion, but solely by the impulse of the mover. Since, as we have sufficiently said, the mover (namely, the immediate mover) and the moved must be together, on which see Physics VII ¹¹, a mobile cannot change its place unless the mover also changes place, either as a whole or in part. For if, while the mobile passes from one place to another, the mover did not change its place, then the mover would no longer be together with the moved.

According to this gloss, the objection concerning the generator of heavy and light bodies, and of the magnet drawing iron, and similar cases, is resolved:

because these things move by imprinting a form through which the things moved are moved, and not by mere impulse from without. For the generator moves heavy bodies by giving them the gravity by which they descend; and the magnet moves iron by imprinting on it the quality by which it is moved toward itself.

It should be noted, second, that by "power in the body" the Philosopher and St. Thomas understand a material power extended along with the extension of the body. For such a power, when the body is moved, whether by rectilinear or circular motion, is moved per accidens. But a power that would be in the body indivisibly would not be moved per accidens if the body were moved circularly, as was shown above ¹² it was shown to be the mind of St. Thomas.

V. Second argument. God is of infinite power. Therefore there is no power in a body, nor is the body itself a body. — The consequence is proved: because no infinite power exists in magnitude, since it cannot exist either in infinite magnitude, because such magnitude does not exist, as is proved in Physics III and De Caelo I; nor in finite magnitude. Therefore, etc. — That it cannot exist in finite magnitude is proved: because it would move in an instant, which is repugnant to motion, as is proved in Physics VI. The consequence is proved: because the effect that a lesser power produces in a longer duration, a greater power produces in a shorter one; but infinite power is greater than every finite power; therefore it will move in a shorter duration than any finite power whatsoever. But not in a shorter time: for then infinite power would move in an equal time with finite power, as is evident from Aristotle's deduction, made by dividing the power. Therefore in an instant.

That God is of infinite power, which was the antecedent, is proved. For He moves through infinite time. But no finite power can move through infinite time: for if this were posited, a part of that body, having a part of the power, would move in less time; for the greater something is in power, the longer a time it will be able to sustain motion; and thus it would follow that finite time measures infinite time, as is deduced by dividing the body and its power into parts.

This argument is manifestly Aristotle's, from Physics VIII ¹³.

VI. Against this argument of Aristotle Saint Thomas brings forward many objections and resolves them ¹⁴. The first objection is Avicenna's, as it is reported by the Commentator, Physics VIII, comment. 78. For Aristotle in his demonstration supposes that the body which causes the first motion is divisible. But this could be denied, and it could be said that that body is not divisible: as is also evident in the case of the celestial body.

Saint Thomas responds (and this is Averroes' response) that a conditional can be true whose antecedent is impossible. And if anything destroys the truth of such a conditional, that thing is impossible. Just as, if something destroyed the truth of this conditional, If a man flies, he has wings, it would be impossible. Aristotle, therefore, does not use this antecedent as true, namely, that such a body is divisible: but rather uses this conditional as true, If that body were divided, its part would be of lesser power than the whole. The truth of which conditional would indeed be destroyed if the first mover were supposed to be a body. Therefore the latter is impossible.

2. But in this response a doubt is raised concerning the truth of that conditional ¹⁵, if we understand it as the Philosopher takes it, namely by comparing the part of the power to the part of the thing moved. For as is the proportion of the whole to the whole, so is the proportion of part to part, and consequently of time to time, as is clear from Physics VII, text 36 ¹⁶. Therefore, in the same time that the whole moves the whole, the part will move the part. Therefore the power of the whole in comparison with the whole moved is not greater than the power of the part in comparison with the part moved.

To this objection, which seems to be against both Aristotle and Saint Thomas, some reply that the proposition assumed by Aristotle, No finite power can move for an infinite time, is to be understood thus: namely, that no power having finite duration can move a mobile that is finite in duration for an infinite time. But with the proposition so understood as needing proof, it is clear that the part of a power in respect of its duration, i.e., the part that endures less, moves a part of the mobile in respect of its duration in less time. From these points it follows that the time of motion cannot be perpetual while both mover and moved are corruptible. Therefore what is adduced from Physics VII is not to the point: because there it is understood with respect to intensity, whereas in this argument we speak with respect to the extension of duration.

3. But it is argued that this response is not Aristotle's meaning. In the proposition under discussion, finite power is taken in the same way in which infinite power is taken in the conclusion to be proved by it, namely, "The power of the first mover is infinite"; for the terms in the premises and the conclusion are taken in the same signification. But in the said conclusion, infinite power is understood not only as regards duration, but also intensively and according to vigor. Therefore, in the premises as well, power must be understood as infinite according to vigor, not only according to duration. — The minor is proved from Aristotle's procedure. For he proves that the first mover is not in magnitude, arguing that an infinite power cannot be in a magnitude, whereas God is of infinite power. He proves the major, however, as regards finite magnitude, because if infinite power were in a finite magnitude, it would move in no time. Now this does not follow from the infinite duration of a power, but from the infinity of its vigor. Therefore, in that proposition, infinite power is understood according to vigor, and not merely according to duration—unless we wish to say that Aristotle equivocated, taking infinite power according to vigor in the major, but infinite according to duration in the minor.

4. But against this exposition, before we answer the doubt, a doubt arises from Aristotle's procedure in Metaphysics XII. ¹⁷ For, when he had shown the perfection of the first substance, in text 42 he inquires whether one such substance alone is to be posited, or several. But in text 43 he concludes that there must be as many substances of this kind as there are motions of the stars, on account of the aforesaid cause: which Saint Thomas, expounding this, says is because they are moved with everlasting motion, and consequently with infinite power.

From these, a twofold argument is drawn against our interpretation. The first is that there are many substances of the same condition as the first. But there cannot be several possessing infinite power in respect of vigor. Therefore the first is not infinite in respect of vigor, but only in respect of duration. Therefore that conclusion, "The first mover is of infinite power in respect of vigor," is wrongly expounded.

The second reason is that there are as many of them as there are motions of the heavenly bodies, on account of the cause assigned concerning the first mover according to the Philosopher, namely that they move with everlasting motion and consequently with infinite power. But they are not infinite powers in respect of vigor, but infinite only in duration. Therefore the assigned cause concerning the first mover, that it is not in magnitude, namely because it is of infinite power, must be understood as referring to infinity of duration, not to infinity of vigor.

5. To make this evident, it must be considered that, since the Philosopher has shown, XII Metaph. ¹⁸ that there must be one substance entirely separate and first, the conditions attributed to that first substance insofar as it is first cannot belong to others, since there are not several firsts: just as what belongs to a man insofar as he is a man does not belong to non-men. Since, therefore, having infinite intensive power belongs to the first substance insofar as it is first, as does being the best and most noble, as will be shown below ¹⁹, the same cannot belong to the other movers of the heavens, since they do not have the character of the first substance. Other conditions, however, which do not belong to it insofar as it is first, can belong to others that share uniformity with it.

When, therefore, the Philosopher says, "Whether there is one such substance or many," the sense is not "Whether there is one that has all the conditions demonstrated above concerning the first, or whether there are many such," for it is certain that there is only one first. But, since he immediately concluded that there is a first substance, eternal and immovable, separate from sensible things, not existing in magnitude, and impassible and unalterable, he inquires whether there is only one such substance, namely eternal, immovable, and impassible. This can be established from the words of St. Thomas. For at the beginning of the lesson ²⁰ he says: After the Philosopher has shown the perfection of immaterial substance, here he inquires about its unity or multiplicity: understand, immaterial substance.

By this the answer to the first argument is clear. For it is said that in the Philosopher there are several substances of the same condition as the first with respect to immateriality, eternity, and impassibility, but not with respect to all conditions.

To the second it is said that, when the Philosopher says there are many for the aforesaid reason, he does not give the reason why the first substance is not in magnitude, but the reason immediately stated in the text of article 43, namely that eternal motion must proceed from an eternal and in itself immobile substance, and that one motion must come from one mover. Hence what Saint Thomas says, that they move with infinite power, is to be understood not according to infinite vigor, which belongs to the first cause alone, but according to duration. For since they move through infinite time, their motive power must be of infinite duration, that is, eternal, which is the same thing. Therefore these substances themselves must also be infinite in duration, that is, eternal.

VII. Returning, therefore, to the principal doubt ²¹, according to the doctrine of Saint Thomas in Book VIII of the Physics ²², it can be answered, first ²³, that Aristotle speaks by comparison to some mark within a magnitude. For thus more time is required for the whole mobile thing to traverse some mark of magnitude than for a part of it to traverse that same mark. The objection, however, proceeds from the whole and the part taken absolutely, not in comparison to a mark of magnitude.

2. But against that reply an objection is urged. First, because Aristotle makes no mention of space, but says there are only three things, namely the mover, the thing moved, and time.

Then, because once a part is cut off from the whole, the velocity is considered with respect to the midpoint of the part and of the whole—not with respect to a point in space, but to the whole space.

Then because Aristotle speaks both of circular motion and of straight motion. In circular motion, however, motion is not considered with respect to a determinate sign in space.

3. For the clarification of these points it must be considered that, since the time of motion is divided in two ways, namely according to the parts of the magnitude over which the motion takes place, insofar as the whole movable passes through one part of the magnitude before the whole; and according to the parts of the movable, insofar as some point of the magnitude is passed through first by one part of the movable than by the whole, and first by one part than by another: in Book VII of the Physics ²⁴, as Saint Thomas says in Book VIII of the same work ²⁵, the whole power is compared with a part of the power according as the time of the motion is divided in relation to the division of the magnitude: for it is true that in the amount of time in which the whole movable, moved by the whole power, passes through some magnitude, in that same amount of time a part of the movable, moved by a part of the power, will pass through that same magnitude; for as is the proportion of the whole power to the whole movable, so is the proportion of the moving part to the part of the movable, if the parts of the mover and of the movable are taken proportionally. In Book VIII, however, of the Physics the Philosopher takes time according as it is divided in relation to the division of the movable. For if a power is constituted from ten parts, as Albert says ²⁶, from which it has it that in ten hours it moves the whole movable, namely by making in each hour one part of the movable pass through some point, it is certain that one part of the power, existing in one part of the mover, will make one part of the movable pass through the said point in one hour. And universally it is true, when time is divided in this way, that a greater power will move in a greater time and a lesser in a lesser time.

To the first objection, then, it is answered that the Philosopher enumerated only those things whose division he needed for his argument, namely the mover, the thing moved, and time. But he had no need of a division of magnitude, since motion was taken by comparison to a determinate sign of it. Therefore he did not enumerate magnitude.

To the second it is said that although, when a part is cut off from the power, the velocity is considered according to the middle point of the part and of the whole with respect to the space, if time is divided for the division of the space; yet if time is divided for the division of the mobile thing, the velocity will be considered with respect to a determinate sign in the magnitude.

To the third it is said that even in circular motion a part traverses some degree of magnitude, whether real or imaginary, in less time than the whole. For in the lower spheres some part of an orb, say the body of a planet, traverses some degree of a higher orb in less time than the whole orb; and the supreme sphere traverses some degree of an imagined higher orb first according to part, and in less time, than according to the whole.

VIII. Second, to the principal doubt it can be answered ²⁷ that Saint Thomas in this passage does not take the part of the mover in relation to the part of the thing moved, as Aristotle took it: but only by comparing it to the duration of the motion. For the greater a power is, the more it can continue its motion and its operation. This is to be understood of a power per se, and not of one belonging to a thing per accidens. For the greater fire is in power, the longer it can continue heating, and so with other things. Therefore a part of that power, as a lesser power, will be able to continue the motion for less time. From which it is clear that that objection against Saint Thomas's argument in no way has force: since he does not assume the proposition that is being attacked.

IX. The second objection which Saint Thomas brings against Aristotle's argument ²⁸ is this. For someone might say that, although the body is divided, there can nevertheless be in the body some power which is not divided when the body is divided, such as the rational soul. And thus the argument does not conclude whereby it is proved that no finite power can move for an infinite time: for it proceeds from this supposition, that in a part of the body there is also a part of the power.

It is answered that throughout the whole course of the principal argument it is not proved that God is not joined to a body in the way in which the rational soul is joined to the human body, for this is of another kind; but rather that He is not a power in the body as a material power is, which is divided by the division of the body. For it is thus established that every such power is lesser in a part of the body than in the whole.

It must be considered, for a fuller understanding of this, that some of the forms by which something acts are in themselves indivisible and are received indivisibly in their subject. This occurs when the whole is in the whole as in its adequate recipient, and the whole is also in each part of its adequate recipient: as the intellectual soul is in the human body. Such a form is not divided with the division of the recipient; for if it is whole in each part, one part of it cannot be in one part of the recipient and another in another. — But some forms, though indivisible in themselves, nevertheless take on division and extension in a subject only per accidens: as whiteness, as color, as cold. For if these were separated from every subject, they would lack all quantitative division; but they are not in a subject such that the whole is in the whole and the whole in each part, but rather the whole is in the whole and a part in a part. Hence, with the division of the subject, they themselves are also divided. Such are called material powers. And that God is not among such material powers is proved on this ground.

X. The third objection ²⁹ is that, if the power of any body is finite, and nothing can endure through an infinite time by a finite power, it follows that the heavenly body is corruptible.

To this objection, first, Saint Thomas brings forward the responses of others and rejects them; second, he sets forth the true solution ³⁰.

2. Some respond, namely Alexander, as the Commentator adduces in VIII Physics, comm. 79, whose opinion is there more fully examined by Saint Thomas ³¹, that the heavenly body indeed of itself is capable of ceasing, but from another, which is of infinite power, it acquires the perpetuity of its duration. To this response the words of Plato in the Timaeus ³², which are also brought forward by Simplicius, on I On the Heavens ³³, seem to lend favor.

But against it one argues on the basis of the Commentator, in XII Metaph., comm. 41. For according to Averroes it is impossible that what of itself can not be should acquire perpetuity from another. For it would follow that the corruptible would be changed into the incorruptible.

3. Therefore the second is the response of the Commentator, who says that in the heavens there is no potency to esse, but only to ubi, according to the Philosopher, Metaphysics VIII, text 12. ** Therefore there is not in it a potency to non-being either. Hence the argument does not conclude, since it presupposes that in the heavens a potency to esse is found.

Against this response Saint Thomas argues that, even if it be granted that in a heavenly body there is no passive potency for esse, there is nevertheless in it a quasi-active potency, which is the power of being. Hence Aristotle says in I Caeli, text 20, that heaven has the power to be forever.

4. It must be noted, with regard to that proposition of the Commentator, that what can of itself not be cannot acquire perpetuity from another, that corruptible and incorruptible are opposites and are distinguished by genus, as is said in Book X of the Metaphysics ³⁴, when they arise from an intrinsic and essential principle. And since one genus cannot be transmuted into another, therefore what is by nature corruptible, or able not to be, cannot become essentially incorruptible. But that something corruptible by nature should become perpetual through something superadded involves no impossibility, as Saint Thomas says, II Sentences, distinction 19, question 2, ad 4, and On Evil, q. 5, a. 5, ad 10: for it always remains corruptible according to its nature. Therefore the proposition of the Commentator, if understood in this sense—that it is impossible for what can of itself not be to acquire from another a perpetuity founded upon its essential principles—is true. But if it means that such a thing cannot acquire perpetuity even through something superadded to its essence, it is false.

It must also be noted, in the argument against the Commentator, that Saint Thomas does not admit as true what he is thought to hold, namely that in the heavens there is no potency to esse, since he himself holds that the heavens are composed of matter and form, as is clear in Book VIII of the Physics, lecture 21, and as will perhaps be explained below ³⁵; but rather as something assumed as true in the Commentator's reply. And even if its truth were granted, the reply does not remove the difficulty.

Concerning what Saint Thomas says, that in the heavenly body there is a sort of active potency, which is the power of being, it must be noted that the power of being pertains to the potency of form, not to the potency of matter, as Saint Thomas says in I On the Heavens, lecture 6. For form, according to its own condition, gives esse to matter, and different forms give different esse. Hence some give corruptible esse, others incorruptible; some more enduring, others less, speaking of variable esse. Now one ought to seek no other reason for this than the very nature of the form, although the condition of matter also concurs: yet this condition must be such because of the nature and condition of the form, and not conversely; for matter exists on account of form, but not form on account of matter. Therefore, since form is not properly an effective principle, yet approaches the causality of an active principle, since we see that every agent acts through some form; therefore Saint Thomas says that the power of being is a sort of active potency, but not simply active.

XI. Second, he gives his own reply ³⁶. And he says two things. First, that because motion, according to its intelligible character, has quantity and extension, therefore its infinite duration requires an infinite motive power. — Second, that although a finite body endures infinitely, it does not follow that the power of being is infinite in a finite body: because esse has no extension of quantity, especially in a thing whose esse is unchangeable, as is the heaven, and therefore it is not reached by time except accidentally. For it makes no difference whether something endures through the power of being for an instant or for infinite time.

To make this reply evident, it must be considered that the greater and more perfect the power of a cause is, the greater a perfection it produces in its proper effect; and conversely, the more perfect an effect is in its own right, the more perfect and efficacious a cause it requires: for causes must be proportioned to their effects. Since motion is the proper effect of motive power, to which extension and successive duration properly belong; and therefore, the longer a motion's duration, the more perfect it is according to this aspect of duration: hence motion of longer duration demands greater power in the moving cause; and if it were infinite in duration, it would require infinite power, otherwise the perfection of the cause would not answer to the perfection of the effect. Therefore Saint Thomas rightly says that infinite duration of motion requires infinite motive power. — He speaks, however, of the motive power that is first, not of the motive power that is proximate and as it were the instrument of the first cause, as he declares in Book 8 of the Physics ³⁷

It must also be known that, since time is the measure of motion first and per se, everything falls under time insofar as it is subject to change and variation. Therefore, although no substantial esse, as such, falls under time of itself, yet if it is joined to motion or variation, it must necessarily be measured by time; but if it is unchangeable, it in no way falls under time. From this it follows that greater power is required for something to endure for a longer time in changeable esse: and if something were to endure in changeable esse for infinite time, there would need to be an infinite power from which it would have infinite duration, just as infinite motion requires infinite power in the first mover. But for something to endure for infinite time in unchangeable esse, infinite power is not required, since that esse does not fall under time, and therefore the infinitude of time contributes nothing to the magnitude of the power. For that unchangeable esse depends absolutely on the form of the thing, from the fact that it is joined unchangeably to potency; and it makes no difference whether it endures only for an instant or for infinite time, since it is in no way measured by time, but by a measure that is permanent and indivisible. Hence what the Philosopher says, that heaven has the power to be forever, is not to be understood as if the very power of being were directly and per se the cause of its perpetuity, but indirectly and consequentially, namely insofar as it gives an unchangeable esse, and consequently one not falling under time and corruption, from which it follows that heaven is forever after it has had that power of being. Hence it has the power to be forever negatively, namely because no time determines a limit to it.

It must also be noted, when Saint Thomas says that unchangeable esse is touched by time only per accidens, that it is one thing for substantial and changeable esse to be touched by time per accidens (for we said above that it too falls under time only per accidens), and another for unchangeable esse. For the per accidens attributed to changeable esse is understood as opposed to what is first, and is the same as what is through another: for it does not belong to it of itself that it be measured by time except because it is subject to variation; yet variability belongs to it per se, though not first. But the per accidens that belongs to unchangeable esse is understood as opposed to what is per se: for it is said to be touched by time because it is conjoined to motion, which is measured by time per se and first, although motion produces no variation in its esse; just as we say that the musician is heated per accidens because he is conjoined to what is heated, although alteration does not vary the musician as such.

The response of Saint Thomas to the doubt, therefore, is that by a finite power something cannot endure for an infinite time if that thing is measured by time either primarily or not primarily but still per se, as is the case with motion and variable esse. But that which has unvariable esse, such as the heaven, can well endure successively for an infinite time by a finite power, because it is touched by time only entirely per accidens.

XII. The fourth objection is ³⁸, because it does not seem unfitting that a mover which is not altered in moving, even though its power is finite, should move for an infinite time. For, since motion consumes nothing of its power, it will be able to move thereafter just as before: just as the power of the sun, which is finite, can by nature act upon these lower things for an infinite time, because in acting its active power is not diminished.

To this objection Saint Thomas responds, first, and second, he removes a certain doubt. He responds, therefore, that that proposition, A finite power cannot move for an infinite time, is to be understood of the finite power of a finite body, and that such a power cannot of itself move for an infinite time. The reason for this is that, since a body does not move unless it is moved, if it happens not to be moved, it will also happen not to move. But insofar as concerns itself, every body that is moved can fail to be moved: because it is moved between the termini of motion, which are opposites. Therefore, of itself it does not befit it to be moved through perpetual time. And thus it does not befit it of itself to move through perpetual time. — But as to what is objected concerning the heavens: — it is said that a body which can of itself be moved and not moved, move and not move, can have the perpetuity of its motion from another; but that other must be incorporeal: on account of which the first mover must be incorporeal. And in this way the sun can move lower things perpetually, not indeed of itself, but by the power of an incorporeal substance.

Second, he removes a doubt that could arise. For someone might say that what can of itself be moved and not moved cannot acquire from another the perpetuity of motion: just as the Commentator says that what can be and not be cannot acquire from another the perpetuity of being ³⁹. — He responds, however, that the reason is not the same for motion as for esse. For motion is a kind of flowing forth from the mover into the thing moved, that is, something unstable, having succession, and consisting in a certain becoming. But esse is something fixed and at rest in the thing, that is, existing all at once as a whole, and not consisting in becoming. Therefore a mobile thing can acquire from another a perpetuity of motion which it does not have of itself, according to the influx of the moving cause. But what is of itself in potency to non-being cannot, by the way of nature, acquire from another the perpetuity of being.

XIII. Concerning this reply, a twofold doubt arises. The first is that, according to the teaching of Saint Thomas ⁴⁰, the motion of the heavens will not cease naturally, but only by divine power. And according to Aristotle it is naturally perpetual. Therefore, insofar as it is from itself, it cannot fail to move: for if from itself and by its own nature it could fail to move, it could naturally be at rest, and thus cease from motion. Therefore that proposition of Saint Thomas is false, that every body which moves is able not to move. The second is that, if a body having finite power can acquire perpetuity in moving from some source, so as to move through perpetual time, then for something to move through infinite time there is not required that it have infinite power, but it suffices that it have finite eternal power. The demonstration of Aristotle assumes the opposite. And thus from the perpetuity of motion he will not demonstrate the first mover to be of infinite power.

2. For the clarification of the first doubt, it must be considered that the motion of the heavens, as Saint Thomas says in Pot., q. 5, a. 5, is not natural to them in such a way that they attain it by means of some natural power inherent in them; rather, because in the heavens themselves there is an aptitude and passive principle for such a motion. Therefore the perpetuity and permanence of the motion of the heavens is not to be considered by comparison with some natural power and form of theirs, but by comparison with the moving intelligence, whatever that may be. From this it follows that, insofar as it comes from the heaven itself—in which there is an aptitude for receiving motion from another—there is in it also an aptitude for not being moved: for if the extrinsic mover were to cease from moving, the heaven itself would not be moved. And universally, everything that is moved, insofar as it is moved, is in potency to being moved and to not being moved, insofar as, if the mover moves it, it is moved, but if it does not move it, it is not moved. For since the termini of motion are opposites, and what is moved is in potency to either terminus, while it is under one terminus it can be moved by the mover to the other terminus, and afterwards cease from motion, should the mover cease to move it.

To the argument, therefore, the consequence is denied. For when it is said that it will not cease naturally, this is understood to mean that in the heaven itself there is no natural power by which it tends toward rest, as heaviness is in heavy bodies, which inclines them toward rest in a place below; but just as it has motion from an extrinsic form, so from that form it will have rest, if ever it should come to rest. — To the proof, the consequence is denied. For although of itself and by its nature as matter it can be unmoved, it does not follow that it is at rest naturally, in the sense in which we here speak of natural rest, namely, that which proceeds from the inclination of a natural form. — As for what Aristotle says, that the motion of the heaven is naturally perpetual, he says this not because he thinks the heaven's motion proceeds from its natural form, but because he judged that the moving intelligence moves it necessarily. Yet this is not repugnant to the heaven's being able, of itself, not to be moved.

3. For the clarification of the second doubt, it must be noted, from the doctrine of St. Thomas in Physics VIII ⁴¹, that since time of motion can be divided in two ways—namely according to the parts of the mobile thing and according to the parts of the magnitude or space—a twofold infinity can belong to motion: namely, according to the parts of the mobile thing, and according to the parts of the magnitude over which the motion takes place. The first would be when a mobile thing traversed some determinate spatial magnitude according to infinite parts of the same quantity, but not of the same proportion; which certainly could not be unless the mobile thing were an infinite body. The second would be if one finite body traversed infinite parts of the same quantity, or traversed the same finite space infinitely many times by repetition. The first infinity belongs to motion per se, as arising from its own subject; the second, however, per aliud, as arising from something extrinsic. — And just as there is an infinity belonging to motion per se, and an infinity that belongs to it through another, so too there is a twofold mover: one, namely, which moves from itself first and does not have from another that it move, such as the first mover; another, however, which does not move per se first, but has from another that it move, namely secondary movers. And thus there can be a twofold cause of the infinity of motion: namely, a primary one, which causes infinite motion per se first and not through another; and a secondary one, which is the cause of infinite motion not per se first, but because it is moved by another. — But since an effect per se must correspond to a cause per se, as we are taught by Aristotle in Physics II ⁴², because the power of a cause is determined not with respect to its effect per accidens, but with respect to its effect per se; therefore that cause which is first and per se, not in virtue of another, causing infinite motion, must be of such power that it could cause infinite motion per se—which is to say, that it could move an infinite body, were such given. And because this requires infinite power, therefore the primary cause of the infinity of motion, which causes it first and by itself, must possess infinite power: but not the secondary cause, which has the perpetuity of moving not from itself first, but from another. Therefore the perpetuity of motion, which is its infinity per accidens, does not argue an infinite power in the secondary agent: because an infinity per accidens can belong even to a finite incorruptible power, from the fact that it moves because moved by another; as was said in ⁴³ that the sun has from another that it perpetually move these lower things.

That this is Aristotle's meaning is evident from the propositions taken from him. For in order to prove that a finite power cannot move a finite thing for an infinite time, he assumes that a greater power moves in a greater time and a lesser in a lesser, which holds true only where the time of the motion is divided according to the division of the mobile, as we showed above ⁴⁴. From which proposition it is concluded that a finite power cannot move for an infinite time, namely taking the time as infinite on the side of the mobile, if the conclusion is to accord with what was premised; and from what follows, that infinite power is required for such an infinite motion. And thus, since that the first cause may be able to move an infinite mobile is required for the first cause of the infinity per accidens of motion, as we showed, it follows that the first cause of the perpetuity of motion must be of infinite power.

To the doubt, therefore, the consequence is denied that what moves is infinite as the first and per se cause of the infinity of motion. But it does follow well that a secondary cause need not be infinite, because it has from another, and not from itself, the power of perpetuating motion. This we concede.

4. But against that determination a doubt arises. Suppose, per impossibile, that there were no cause of infinite power, but there were some eternal intelligence of finite power; such an intelligence could sustain perpetual motion: for, as Saint Thomas says in Physics VIII,⁴⁵ in order for something to be the cause of infinite motion by reiteration, it is not required that it have infinite power; it suffices if it have finite unmoved power. Therefore eternal motion does not necessarily argue an infinite power in some cause.

It is answered first that, in that case supposed—though it is impossible—that intelligence would indeed cause the perpetuity of the motion, from the fact that its motive power would be perpetual and immobile; yet it would not cause it as the first and per se cause of such perpetuity: for this would not be by reason of its own proper power, but by reason of a condition conjoined to it, namely, the immobility and perpetuity of its power. And then an effect would be posited without its first and per se cause, which is impossible. Nor is it any wonder if, one impossibility being posited, another impossibility follows. But if it be argued: "That intelligence would be the first cause, because it would have no other prior to itself; therefore it would be the first and per se cause of the perpetuity of motion"—the consequence is denied. For it can stand that something be first in some order by reason of some supposition made, and yet not be the first and per se cause of some effect: just as Adam is the first man, and yet is not the first and per se cause of man insofar as he is man.

To the second it may be answered that, given that case, such an intelligence would not cause perpetual motion: since it would not have the power to cause it except as moved by an intelligence of infinite power. — But when Saint Thomas says that for the eternity of motion it suffices, by reiteration, to have a finite immobile power: this is understood on the supposition of a first infinite mover. Therefore, that being removed, it would either not move at all, or for a certain and determinate time. — But if it be urged that that substance would always remain the same; and that the same thing, remaining the same, is naturally inclined always to do the same: — it is said in the same way that, speaking of a cause which by its own nature moves as moved, the same thing, remaining the same, is naturally inclined always to do the same, while the influence of the first cause remains: but not when that is removed.

XIV. The fifth objection is⁴⁶. Just as from infinite power being in a magnitude it follows that it moves in no time, so also if it were outside a magnitude. Therefore, from the fact that it is impossible for power to move in no time⁴⁷, it does not follow only that infinite power is not in a magnitude, but that no power is infinite absolutely.

2. Saint Thomas answers this objection in three ways⁴⁸. First, according to the Commentator, Physics VIII, comm. 79, that the potentiality which is outside magnitude is finite or infinite only equivocally. Therefore, from its infinity it does not follow that a finite proportion is removed in other things, namely in times and motions. But that which is in magnitude is finite or infinite according to the same account as time and motion: because the finite and the infinite are found in the same way in magnitude, motion, and time, as is said in Physics III and VI. Therefore the infinite in one of them removes a finite proportion in the others.

Note that the Commentator says finiteness and infiniteness equivocally belong to separate power and to quantities, because in them it does not belong according to one and the same account. For in quantities, finite and infinite are said according to a certain extension, and according to the privation of the end of the quantity; but in a separate form, they are said according to perfection. Therefore, according to him, power outside magnitude and power in magnitude are not comparable. Although Saint Thomas does not reject this response of the Commentator here, he nevertheless rejects it in Physics VIII⁴⁹, as we shall bring forward in the second response.

XV. Second, it is answered, according to the mind of the Commentator as well, Metaphysics XII, commentary 41, that since the heaven has two movers—namely a proximate one, which is of finite power, and a remote one, which is of infinite power—from the proximate one it has the finite velocity of its motion, but from the remote one its infinite duration. On account of this, if a power that is infinite were outside magnitude, it would not follow that it moves in an instant: for it can move a body mediately. But if an infinite power were in a magnitude, it would of necessity move in an instant: for it must move the body immediately, since a body is not moved except by being moved by another.

The sense of this reply is that, since a power outside magnitude moves through the mediation of a power existing in the magnitude, its action is limited by the power existing in the magnitude; for the power of the first cause operates according to the condition and nature of the second cause. For we see that the sun generates a man by means of a man, and a horse by means of a horse. Therefore, if the power existing in the magnitude is finite, and consequently naturally apt to move with a finite velocity, an infinite power outside the magnitude, moving through its mediation, will not move with infinite velocity but with a finite and determinate one. But the power existing in the magnitude, because it moves the heavenly body itself immediately—otherwise it would not move the lower bodies, since a body does not move unless moved—if it were infinite, would necessarily move in no time: for it cannot receive limitation from a second cause, since it moves not through another cause but immediately through itself.

2. It must be noted, however, that Saint Thomas considers this first response the better one, although he also says of it in VIII Phys.⁵⁰ that it is insufficient, because the first response is against Aristotle: since Aristotle himself posits that the power which moves for an infinite time is infinite and outside magnitude; from which it appears that the infinity of such a power is comparable to the infinity of time according to the proportion of cause and effect, although the infinite is not found in them according to the same ratio. — It is also false that the infinity of a separate power does not take away the proportion between the duration of its motion and the duration of the motion produced by a finite power. For the speed of motion follows the magnitude of the power of motive force which belongs to it per se, which is the magnitude of perfection: not, however, that which belongs to it per accidens, namely with respect to the extension of the subject. For the more perfect a power is, the more active it is, not the more extended: for intense heat in a small quantity heats more than remiss heat in a large quantity.

The second response, however, does not remove from a separate power a finitude or an infinity comparable to motion and time according to some proportion of cause and effect. Nor does it take away from the infinite separate power that it could move, insofar as it is in itself, in an instant. For according to this response, if it moved immediately, it would necessarily move in an instant; but because it moves mediately, it can move in time. Now the motion of the heavens, according to the Commentator, has a finitude of velocity from its proximate mover, because it is of finite power. Therefore on this account the second response is better than the first.

3. It must also be noted that Saint Thomas seems to think that the Commentator understood the infinity of the first mover differently in Metaphysics XII⁵¹ than he did in Physics VIII⁵² For in Metaphysics XII he grants that it is infinite, but in Physics VIII he denies it, as he also seems to deny it in De Caelo II, comm. 38, 39; 63 and 71, and in De Substantia Orbis, chapter III, when speaking of the infinity of vigor. — But if anyone wished to hold that the Commentator does not understand it differently, but everywhere held that God is not of infinite vigor, one could reply to the authority of Metaphysics XII, in conformity with what is said in Physics VIII, that Averroes does not grant that God has infinite power in vigor, but has a certain infinitude said equivocally with the infinitude of virtue existing in matter, by which he acts toward the eternity of motion. Therefore, if such a virtue outside magnitude is posited as infinite in its own way, that is, not limited nor finite as those things are which are of the genus of quantity, it does not follow that it would move in no time: for that infinitude is not comparable to the infinitude of the velocity of motion, since it is of another kind from quantitative things. But if there were infinite virtue in a magnitude, it would move in an instant: because it would have an infinitude comparable to infinite velocity, inasmuch as it would be quantitative according to the same ratio as time and motion. For according to this virtue, namely that which is in matter, velocity and slowness of motion are to be considered: a sign of this is that on account of the finitude of the virtue which is in the orb as its soul, the velocity of its motion is finite. — But if anyone wished to hold that according to the mind of the Commentator God is of infinite vigor, one could say regarding the statement in Physics VIII that He is neither finite nor infinite with an infinitude from which motion in an instant would follow: for that infinitude of vigor which is outside magnitude is not quantitative, so as to be compared with the intensive quantity of motion; though it is compared with extensive quantity, namely with His eternal duration, because He Himself possesses both eternity and perpetuity. For eternity is not limited to the genus of quantity, since it is found in non-quantitative things; but intensio is found only in quantitative things, since it depends upon participation in a material subject. — As for the other passages in which he seems to say that there is no virtue infinite in vigor, it could be said that he speaks of conjoined virtues, which are called the souls of the orbs, and not of virtue separated from matter.

Third ⁵³, an answer is given still better, and it is said that the power which is not in magnitude is intellect, moving through will; but that which is in magnitude is not intellect, because intellect is not a power in a body; hence it moves not through intellect and will, but through the necessity of nature. For this reason that which is outside magnitude moves, not according to the property of its power, but according to the exigency of the mobile thing. Therefore it does not follow that it moves in an instant. But that which is in magnitude, namely as a material power extended with the extension of its subject, as we explained above ⁵⁴, moves according to the property of its nature and power: just as a body moves according to the property and condition of its quantity. Therefore it follows that it moves in an instant. — You have the explanation of this answer in Book VIII of the Physics ⁵⁵ by Saint Thomas.

2. Nevertheless, for a fuller understanding of what is said here and there, it must be considered that the first cause of perpetual motion, if it is posited as infinite in power, whether it is posited within magnitude or outside magnitude, can, as far as its power's condition goes, move in an instant. For just as no finite power is proportioned to it in strength, so, of itself, it can cause motion proportioned to no finite motion in speed. Hence an infinite power within magnitude and one outside magnitude do not differ with respect to being able to move in an instant, as far as the sufficiency of the power is concerned; nor do they differ with respect to not being able to move in an instant because of the resistance of the movable thing, for this is common to both powers. But they differ with respect to the exercise of this power and with respect to moving in act. For if it is posited outside magnitude, it will not move according to the whole of its capability and according to the condition of its nature, but according to what befits the nature of the movable thing and the end conceived beforehand by such a substance; and because the nature of the movable thing does not admit it, nor does the intended end require that the motion be in an instant, therefore it will not move in an instant, but in time. If, however, it is posited within magnitude, it will move according to the condition of its nature as a material form, and according to the whole of its capability. Therefore it will necessarily move in an instant. Hence the Philosopher does not make this conditional, If an infinite power is within magnitude, it could move in an instant: but this one, If it is within magnitude, it will move in an instant.

3. But this response is better than the second, because the latter did not explain why, given an infinite power existing outside magnitude, it does not follow that it moves in an instant. For what was said—that this is because motion has its velocity from the proximate mover, and that this is of finite power—does not satisfy. For just as a proximate agent cannot move in an instant by its own power, so it cannot move for infinite time; but the first agent can do both of itself. For one may ask, since moving through perpetual time belongs to it by the power of the first mover, which cannot belong to it by its own proper power, why does not moving in an instant likewise belong to it in the power of the first agent, since both are contained in the power of the first mover? And thus no sufficient reason is assigned why the motion of the heavens should be of finite velocity, given an infinite power existing outside magnitude, namely that the proximate mover is of finite power; for by the same reasoning it ought to be of finite duration. — The third response, however, sufficiently explains why an infinite power outside magnitude does not move in an instant, while an infinite power within magnitude indeed can, as appeared.

4. But a doubt arises. For material power and force do not always act according to the condition of nature and according to its whole power absolutely, but according to its power in relation to the disposition of the subject. For the heat of fire does not always heat according to how it could heat absolutely, but according to how the subject is disposed to be heated. Hence the same heat heats one thing more, another less. Therefore, since the infinite power is in magnitude and is material, it does not follow that it moves according to its whole power, but according to the disposition of the mobile. Now no mobile is disposed so as to be moved in an instant. Therefore it does not follow that it moves in an instant, but in time.

It is answered that it is one way with a finite material power and another with an infinite one. For something can resist a finite power according to some proportion, but not an infinite power, since nothing finite has proportion to the infinite. Hence it comes about that a finite material power is sometimes impeded from acting according to its whole capacity absolutely, on account of the indisposition of the subject resisting the power; but an infinite power cannot be impeded by the subject's indisposition from acting according to its whole capacity, since no finite resistance has proportion to infinite virtue. For if there were fire of infinite heat, it would heat according to its whole capacity, and could not be impeded by any indisposition of the subject. Therefore this conditional is true and necessary, If infinite power were in a magnitude, and consequently material, it would move in an instant, even given that the mobile thing is not of itself disposed to instantaneous motion with respect to a finite virtue. Nor is that proposition, Material virtue does not always act according to its whole capacity, but according to the disposition of the subject, true of infinite virtue; but it is indeed true of finite virtue, as is proved.

XVII. It must be noted, however, that besides the answer given here, St. Thomas touches upon another in Book VIII of the Physics ⁵⁶ and in the First Part, q. xxv, a. 2, ad 3: namely, that the reason for the difference between an infinite immaterial power and a material one, with respect to moving in no time, is that a mover outside magnitude is not a univocal agent, but one of a higher order. Hence it is not necessary that magnitude be receptive of the whole of its effect. Therefore, since by virtue of its efficacy two effects belong to it—namely, the eternity of motion and instantaneous motion—it is not necessary that magnitude be receptive of both effects, such that its whole power be manifested in the motion of a body. Therefore, although a body may be receptive of eternal motion from an infinite immaterial substance, it need not nevertheless be receptive of motion in no time. — But a corporeal mover, in moving another body locally, is a univocal agent: inasmuch as it moves only locally, and is itself moved. Hence nothing prevents an effect proportionate to the power existing in magnitude from being received in magnitude. And therefore, if it were infinite, the effect proportionate to it, namely motion in no time, would be received in the mobile thing. Since this is impossible, it follows that it is impossible for infinite power to exist in magnitude.

XVIII. The third argument for the principal thesis ⁵⁷ is this. The first motion is continuous and regular. Therefore the first mover is not a body. — The consequence is proved. Because continuous and regular motion cannot come from a bodily mover, since such a mover moves by attracting or expelling; but in such motions the thing moved is not always in the same disposition toward the mover, but is sometimes nearer, sometimes farther. — This argument has its foundation in Book VIII of the Physics, where it is proved that the first motion is continuous and regular.

It must be noted that the proposition, No motion from a corporeal mover can be continuous and regular, is true if the motion is from a corporeal mover as from a first and principal mover; but not if it is from it as from an instrument. For the motion by which the lower spheres are moved with the diurnal motion is continuous and regular, even though it is from the first movable body: because it is not from it as from a principal mover, but as from the instrument of the moving intelligence.

2. But a doubt arises concerning this argument: because it seems to rest on a false foundation. For a local mover does not always move by attracting or expelling, but also by pushing. Hence the Philosopher, in VII Physics ⁵⁸, reduces other local motions by which something is moved by another not to attraction and expulsion, but to pulling and pushing, which is a kind of expulsion and impulsion. Nor does it seem true of attraction that the mobile is sometimes nearer to, sometimes farther from the mover: for the thing pulling is never separated from what is pulled, as is said in VII Physics⁵⁹.

It can be answered, as far as occurs to me at present, that this argument supposes the first mover does not change its own place in moving the thing moved by it, since it has been shown to be immobile⁶⁰. Now it is evident that such a mover moves another body only by expulsion or attraction, in which the thing moved either makes itself stand apart from it, or makes what stands apart approach it, whether as a whole or in part. But in both ways it happens that the thing moved is at one time nearer to the mover and at another farther away.

When, however, it is urged that the pulling thing is never separated from the pulled thing: — it is said first that, supposing the pulling thing is not moved, it is false that it is never separated from the pulled thing; rather they are joined only at the end, as is clear when a magnet attracts iron. For a body that is not moved can pull in no other way than the magnet pulls iron, namely by the impression of some form on account of which the pulled thing is moved toward the pulling thing. But what Aristotle says, that the pulling thing is never separated from the pulled thing, is understood of what pulls by local motion alone, not however by the impression of some form. Hence traction is taken here in one way, and in another way in Book VII of the Physics.

It is said second that, although the mover is never entirely separated from the thing moved—that is, it must be joined to what is moved either according to the whole that is moved or according to a part—it need not always be joined to it according to the whole, but it suffices that it be joined according to a part. And this would happen if the extrinsic mover of the celestial body were a body existing in a determinate position, say in the east. For, by expelling from itself one part, to which it is immediately joined, through the upper hemisphere, it would draw to itself another part, which moves from west to east, through the lower hemisphere; and thus it would be joined to what is moved not according to the part that is moved, but according to the part that is expelled.

XIX. The fourth argument⁶¹. The end of the first motion cannot be a body or a power in a body. But God is the end of the first motion. Therefore He is neither a body nor a power in a body. — The major premise is proved. Because the end of perpetual motion must always be, and in every way in act: since motion that is toward an end passing from potency into act is not perpetual, as it ceases once act has been reached. But no body or power in a body is of this kind, since it is moved either per se or per accidens. — The minor premise, however, is proved. Because the end of the first motion is the first mover, which moves as the desired. — This argument also has its foundation in Book VIII of the Physics⁶², where it is shown that a power in a body is moved either per se or per accidens.

2. But concerning this argument a doubt arises: for there seems to be no difference, with respect to motion, between an end that passes from potency into act and an end that is always in act. For it is universally true that, once the end is attained, motion ceases: for once health, which is brought forth from potency into act, is attained, healing ceases; and once the place below, which is an end preexisting in act, is attained, the motion of the heavy body downward ceases. And so it will follow that, if there is some end of the first motion, it can in no way be perpetual.

It is answered that the proposition, "Once the end is attained, motion ceases," is not true of every end, as is stated in IV Sent., d. XLVIII, q. II, a. 2, ad penultimam rationem in oppositum; rather, it holds true only of an end that follows upon the motion, for such an end is related to the motion as a terminus to a road. But of an end that accompanies the motion it does not hold true. Now the end of celestial motion is assimilation to God in causality, as it were an intrinsic end; for the extrinsic end, of which this argument speaks, is God himself. This assimilation to God, however, accompanies the very motion. Therefore the motion of the heavens does not cease once this end is attained; indeed, the heaven moves perpetually on account of this end, namely that it be maintained in being attained. Moreover, the perpetual uniform motion is preserved on account of the immobility of God himself. From this it follows that the heaven, by its uniform motion, is always assimilated to him in causing.

XX. But since the arguments set forth above proceed on the supposition of the eternity of motion, whose opposite the faith holds, someone might believe those arguments to be ineffectual. Therefore Saint Thomas shows that they do not on this account lose their efficacy. For although the faith holds that the motion of the heavens will at some time cease, it does not posit that this will happen either because of the impotence of the mover or because of the corruption of the mobile thing, since in either way that motion would grow sluggish through the long passage of time, as appears in these lower things; rather, it believes that it will cease by the will of God. Therefore Aristotle's arguments are founded upon what is possible in nature. This being granted, they are most efficacious, even though we hold that the opposite is the case de facto.

Finally, the conclusion is confirmed by the authorities of Sacred Scripture: namely, John 4, "God is a Spirit"; likewise 1 Timothy at the end, "To the King of ages," etc.; likewise Romans 1, "The invisible things," etc.

XXI. As to the third⁶³, a threefold class of errors is excluded: namely, that of the Physicists, who all, except Anaxagoras, held God to be a body; that of the pagans, who held the elements of the world and their powers to be gods; and that of the Jews and other heretics, namely Tertullian and the Vadiani or Anthropomorphites, and others who fashioned God with bodily lineaments; as well as that of the Manichaeans, who held God to be a certain infinite substance of light. The occasion of all these errors was that, in thinking about divine things, they had recourse to the imagination, through which nothing but the likeness of a body can be grasped. — It should be noted that "Anthropomorphite" is a Greek word, compounded of anthropos, which means man, and morphe, which means figure. Thus they were so called because they described God in human figure.