Commentaria in Summam contra Gentiles, Liber III

After St. Thomas has shown what sort of order exists among intellectual substances, he wishes to determine concerning the order of bodies ¹.

I. And he posits this conclusion: Lower bodies are disposed by higher bodies.

It is proved first. Lower intellectual substances are ruled by higher ones, so that the disposition of divine providence descends proportionally all the way down to the lowest things. Therefore lower bodies are also ruled by higher ones. — The consequence is proved. Because in bodies also there is higher and lower, just as in spiritual substances.

2. Second. Celestial bodies are higher in place. Therefore they are more formal. Therefore they are more active. Therefore they act upon lower bodies. Therefore etc.

The first consequence is proved. Because by as much as any body is higher in place, by so much is it found to be more formal. — It is proved by a sign. Because the higher place is the place of the lower body. Which is a sign that it is more formal: since it belongs to form to contain, just as it does to place. — It is also proved from the order of the elements.

Note, concerning the proof of the antecedent by a sign, that St. Thomas does not intend to argue in the second figure thus: It belongs to form to contain; A higher place contains the lower; Therefore it is a form: for then the argument would be in the second figure from purely affirmative premises, against the rules of syllogisms. But he intends to argue from the likeness and proportion of place to form in respect of containing, arguing thus: Form and place agree in containing. Therefore that place which contains another approaches more to the character of a form. But a higher place contains the lower. Therefore it is more formal than it.

It should be observed, however, that although it belongs both to form and to place to contain, this is nevertheless in different ways. For place is said to contain quantitatively, insofar as it comprehends in itself the quantity of the located body. But form is said to contain formally and virtually, insofar as it gives being and species to the body: for as long as it remains under the form, it retains its being and its species; but when the form departs, it loses both being and species.

Concerning the proof of the first consequence, and the other consequences adduced, it must be considered from the teaching of St. Thomas on II De Caelo, lect. 20 ², that, since the container has the character of that which determines and bounds, while the contained has the character of that which is terminated and bounded, a body that naturally contains another body is reasonably posited to have more of the character of form than that which is contained: for it belongs to form to determine and bound, but to matter to be determined and bounded by form. And because, by as much as a body is higher in place in the natural order, by so much is it compared to lower bodies as container to contained, it is therefore fittingly said that it is also more formal. — But because form is act, therefore such a body is also more actual than the others. — And because every agent acts through its form, it also follows that it is more active.

II. Third ³. Celestial bodies are perfected in their natures without any contrariety; but lower bodies are not perfected in their natures except with some contrariety. Therefore celestial bodies are of more universal power than lower bodies. Therefore they move and dispose them.

The antecedent is proved exemplarily in certain contrarieties. — And from motions. Because to the circular motion of celestial bodies there is nothing contrary, and therefore in them there can be no violence; but the motions ⁴ of lower bodies are contrary.

The first consequence is proved ⁵. Because that which is perfected in its nature without contrariety is of more universal power than that which is not perfected except in contrariety. — It is explained. Because contrariety arises from the differences that contract a genus. — A sign of this is that in the apprehension of the intellect, because it is universal, the species of contraries are not contrary.

The second consequence is proved. Because universal powers are motive of particular ones.

2. Concerning the antecedent, it must be considered that lower bodies are perfected in their nature with contrariety can be understood in two ways. In one way, because their nature is composed of contraries. And it is not understood in this way here. For the elements, which are among the number of lower bodies, since they are simple bodies, are not composed of contraries.

In another way it can be understood because some quality follows upon their nature and their natural form, to which the quality of another body is contrary. And in this way it is understood. For dryness and heat accompany the nature of fire, to which the moisture and coldness of other bodies are contrary. But no quality of this kind accompanies the nature of celestial bodies.

III. Concerning the proof of the antecedent ⁶, a doubt arises. For the motion of a celestial body from west to east seems to be contrary to its motion from east to west: since they are to maximally distant places. Therefore it is false that nothing is contrary to the motion of celestial bodies.

It is confirmed. Because straight motion is contrary to circular motion.

2. For the evidence of this, it must be considered from the teaching of St. Thomas on I De Caelo, lect. 8 ⁷, that, since circular motion is from the same to the same, two maximally distant termini cannot be assigned in it that terminate that motion as terminus a quo and terminus ad quem: for even if some point is maximally distant from the terminus from which the motion begins—namely, that which is diametrically distant from it—that is nevertheless not the terminus of such a motion, but has the character of a middle. Whence it happens that such a motion cannot be said to be between contrary termini. Hence the motion of the first moved body from east to west is not from these points as from terminus to terminus, but as from terminus to middle, through which that moved body returns to the east. From this it follows that the motions of a celestial body cannot have diversity among themselves in such a way as to be motions made between contrary termini, as are upward motion and downward motion, of which one is from the center to the circumference, the other from the circumference to the center: but because what is the terminus of the one is the middle of the other, to which they arrive by contrary ways; just as the first moved body, which is moved from the east, returns to the east passing through the west, which is the terminus of the motion from which the motion of the planets begins, and at which it terminates; and conversely the motion of the planets, beginning from the west, passes through the east, which is the beginning of the motion of the first moved body. Moreover, these moved bodies arrive by different ways at that which is the middle of the motion of the one moved body and the principle of the other: for the first moved body, passing from the east toward the west through the upper hemisphere, returns to the east through the lower hemisphere; but a planet, passing to the east through the lower hemisphere, returns through the upper hemisphere to the west. And thus the east is arrived at by both motions through different ways. Which does not make a contrariety of motions, but a diversity. Therefore those motions of celestial bodies are not contrary, although they are diverse.

St. Thomas also touches upon two other reasons there why these motions are not contrary. One of which is that those motions are not upon the same poles: since one is upon the poles of the world, but the other upon the poles of the zodiac.

The other is that they are not in the same circle, but the motion of the planets is in lower circles: and consequently they are not between the same termini, nor do they take place across the same distance. Now contrariety must be regarded in respect of the same distance: as is evident in straight motions, the contrariety of which consists in the distance of the center and the circumference.

3. To the argument, therefore, it is denied that the motion of celestial bodies from west to east, returning to the west, is contrary to circular motion from east to west, and returning to the east.

When it is proved because they are between maximally distant termini: — it is said first, that this is false. Because the east is the terminus a quo and the terminus ad quem of one of those motions, and the west of the other.

It is said secondly that, although east and west are taken in the same circle as two maximally distant termini as their distance is measured by the diameter, which is the greatest straight line drawn from one point of the circumference to another point, they are nevertheless not maximally distant as they are termini of a motion made upon a curved line. Nay rather, in the motion of the first moved body, the point that, while the moved body recedes from the west, approaches nearer to the point of the east from which the first moved body first receded, according to distance measured by a curved line, proceeding according to the order of motion, is further distant from the point of the east than the point of the west. For example: let there be a circle A B C D, such that A and C are diametrically opposed. In proceeding from A to B, and to C, and to D, and finally returning to A, D is more distant from A than C is, because the arc between A and D is greater than the arc between A and C. Just as in the zodiac the distance between the beginning of Aries and the beginning of Capricorn, proceeding from Aries to Taurus, and successively, according to the order of the signs, returning to the beginning of Aries, is greater than between the beginning of Aries and the beginning of Libra, which are diametrically opposed: for the arc between the beginning of Aries and the beginning of Capricorn, according to the said order, is greater than the arc between the beginning of Aries and the beginning of Libra, since the latter is a semicircle, while the former is greater than a semicircle. And, to state it briefly, in a circle there are not two maximally distant termini, if their distance is measured by a curved line or arc: unless perhaps there were given two immediate points in a circle, of which one would be the beginning and the other the end; which is clearly impossible.

It is said thirdly that, positing that there were two maximally distant termini, it still does not follow that such motions are contrary. Because beyond this, it would be required that those motions be upon the same axis, and upon the same poles. Which does not happen in the present case.

4. To the confirmation ⁸ it is said, according to St. Thomas in the same place ⁹, that if straight motion is contrary to circular motion, this is only by reason of the differences of the same genus: for differences of the same genus are contrary, as is said in X Metaphysics ¹⁰ (according, however, as contrariety is taken for the excess and defect of differences under the same genus, as St. Thomas explains on V Physics ¹¹). But these motions are not contrary by reason of their species, according as one species is corruptive of the other, in which way we say that nothing is contrary to the motion of celestial bodies. For it is not unfitting that there be contrariety in this way in celestial bodies: just as there is contrariety according to even and odd, and the like, although there is no corruptive contrariety there.

IV. Concerning the proof of the first consequence ¹², when it is explained from the condition of the intellect, it must be observed that the sense of that explanation is that, because our intellect is universal in its apprehension, that is, it is not limited to apprehending this limited nature rather than that; nay, it can even apprehend the very nature of a genus without any determination to any species, and can be perfected without determination by any difference contracting the genus: therefore the species of contraries in it have no contrariety, although they represent contraries. For the illimitation and universality of the intellect brings it about that it is foreign to all contrariety, and that in it all intelligibles, however contrary they may be in their proper natures, can be gathered together without contrariety. And this is a sign that the contrariety of one nature to another arises from its limitation by some difference contracting the genus.

It should be observed, however, that it is not to be understood that contrariety arises from limiting differences as if all species that are constituted by the differences of the same genus were contrary, or had contrary qualities: but because in those species in which contrariety of this kind is found, this arises from their differences. From this, moreover, it follows that a nature which is perfected without any contrariety is of more universal perfection and power than a nature that is perfected in some contrariety. For if contrariety follows the limitation of a nature by some difference, it follows that a nature that is far removed from all contrariety is limited by none of those differences from which contrariety arises, but is above all natures and differences of this kind; and consequently that it is not limited to the operation of only one of such natures, say of fire or of air, but by its power exceeds each of such natures, and thus is of more universal power.

V. Fourth ¹³. Celestial bodies are more like separate substances than other bodies are, insofar as they are incorruptible; and they are closer to them, insofar as they are moved by them immediately. Therefore etc. — The consequence is proved. Because by intellectual substances all other things are ruled.

Fifth. Things that approach nearer to immobility ought to be motive of other things: because the first principle of motion must be something immobile. Celestial bodies are more immobile than lower bodies: insofar as they are moved by only one species of motion, namely local motion, whereas lower bodies are moved by all species of motion. Therefore etc.

2. Sixth ¹⁴. The motion of the heaven is first among all other motions. Therefore it is the cause of all other motions. — The consequence is proved. Because the first in any genus is the cause of those that come after.

The antecedent is proved. Because local motion is first among all motions, in time, in nature, and in perfection. And similarly circular motion is first among local motions. And only the motion of the heaven is found to be regular and uniform. — The first part is proved. Because local motion alone can be perpetual, as is said in VIII Physics, text 54 ¹⁵. And without it there cannot be any of the other motions: as is clear by running through the species of motion. And it does not vary a thing according to something inherent in it, namely something absolute, but only according to what is extrinsic, namely according to place: and therefore it belongs to a thing already perfected. — But the second part is proved. Because circular motion alone can be perpetual, as is proved in VIII Physics, text 64. And it is more simple and one: since it is not divided into beginning, middle, and end, but is whole as it were as a middle; and it bends back to the beginning. — But the third part is proved from comparison to the motions of heavy and light things, which are intensified at the end.

Concerning the proof of the antecedent, it must be considered first, that prior by nature is sometimes taken as it is distinguished against prior in duration: and thus both what is prior in the order of generation, and what is prior in perfection, is called prior by nature. But sometimes it is taken as it is distinguished against prior in the order of generation: as, I say, it is the same as prior in perfection. When it is said here that local motion is naturally prior, it is given to be understood that prior by nature is taken in the first way, but not in the second way, since it is distinguished against prior in perfection: for in this way local motion is prior in the order of presupposition, insofar as it is presupposed by all other motions.

It must be considered secondly, that circular motion is said to be whole as it were as a middle, and not to be divided into beginning, middle, and end, because in circular local motion there is no taking any point from which the whole moved body begins to depart, and any to which it finally arrives: since the whole simultaneously changes place conceptually, but not in reality; and in a circle no point is beginning and none is end, except according to the designation of the intellect.

VI. But concerning the aforesaid, a manifold doubt occurs. The first is: Motion receives dignity and perfection from the terminus ad quem: as St. Thomas holds in the Prima Pars, q. xlv, a. 1, ad 2. But the terminus ad quem of local motion is not more perfect than the terminus ad quem of other motions, and especially of generation. Therefore it is not more perfect than other motions, as was being said.

The second is ¹⁶. Where there are no extremes, there is no middle: since a middle is not spoken of except in relation to extremes. Therefore, if circular motion is not divided into beginning, middle, and end, it cannot be said to have the character of a middle as a whole.

The third is ¹⁷. A motion that does not have a beginning and an end is perpetual. Therefore, if circular motion does not have a beginning and an end, every circular motion will be perpetual. This is false. Therefore etc.

The fourth is ¹⁸. Circular motion is always at the end, as is said in I Meteorology ¹⁹. Therefore it is false that it is not divided into beginning and end.

VII. To the first of these, some answer that motion can be taken in two ways: in one way, as to its entity, according to which it exists, and according to which it is the same as the terminus; in another way, according to its formal character. If it is taken in the first way, it is thus conceded that local motion is not more perfect than the others. — But if it is taken in the second way, it is thus more perfect than the others. Because, since motion is compared to its terminus as potency to act, and as imperfect to perfect; by how much the terminus is more imperfect, by so much the motion is more perfect, because it is the privation of a lesser perfection; just as, by how much the terminus is more perfect, by so much the motion is more imperfect, as being the privation of a greater perfection.

2. But although that answer is that of most learned men, namely Capreolus, on II Sentences, d. xiv ²⁰, and Paulus Soncinas, VII Metaphysics, q. xxv, it nevertheless does not seem to me to be true, nor to be according to the mind of the Philosopher and St. Thomas. For from whatever a thing has species, from that it receives the dignity and perfection belonging to it from its character: since the essential perfection of a thing consists in the perfection of its species. But it is clear from V Physics ²¹ that motion receives its species from the terminus ad quem. Therefore it also takes its perfection from it. If therefore the terminus ad quem of local motion is more imperfect than the termini of other mutations, local motion according to its formal character cannot be more perfect than other mutations. And thus it is repugnant that, insofar as it is the same as the terminus, it is more imperfect than others; and that according to its proper character, it is more perfect.

3. Therefore it seems to me that it should be said that, since motion implies a respect to the moved body, and to the terminus of motion, from the fact that it is the act of the moved body insofar as it is movable ²², or insofar as it tends to the terminus of motion, we can speak in two ways of its perfection: in one way, of that which belongs to it from its order to the terminus of motion; in another way, of that which belongs to it from its order to the subject. The first belongs to it formally and from its proper character: as belonging to it from that from which, insofar as it is motion, it receives species. But the second belongs to it materially and extrinsically: as belonging to it from the moved body, which is its matter. If therefore change of place is considered as to its formal perfection, it is thus not more perfect than other mutations, but more imperfect. — But if it is considered as to its material and extrinsic perfection, it is thus more perfect than other mutations: which is to say that its subject is more perfect and more actual than the substances of the others. For local motion requires its subject, insofar as it is such, to be in potency either to something extrinsic only, namely to place; or in potency to where, which implies a relation; but not in potency to any intrinsic absolute form. But all other mutations require a subject in potency to an intrinsic form, either substantial or accidental: since they vary the subject from form to form.

The first statement is shown, first, by the authority of St. Thomas, in the Prima Pars, in the place cited ²³, where, speaking of mutations taken formally, he maintains that motion receives dignity and perfection from the terminus ad quem. — Secondly it is also shown from De Malo, q. xvi, a. 10. For there, from the order of motions that belongs to them according to their proper character, he argues that a spiritual substance can move bodies locally, although it cannot move them formally, because weak effects can be produced immediately by a more remote agent. For it is clear that in this reason it is included that change of place, according to its character, is both weaker and more imperfect than other mutations.

The second statement is proved because Aristotle, in VIII Physics, text 58 ²⁴, explains that this motion is more perfect than the others from the perfection of the subject. Whence the Commentator forms his argument in this way: Translation belongs to a more perfect thing. But what belongs to a more perfect thing is more perfect. Therefore etc. For it is clear that this proposition, What belongs to a more perfect thing is more perfect, holds true regarding the perfection of the matter of the form.

Both of the last-mentioned points are shown at the same time from the reply which St. Thomas gives to the first argument, in the passage cited in the Questions on Evil. For when he had argued that a spiritual substance cannot move bodies locally, because local motion is more perfect than the other motions, yet it cannot move by the other mutations, he answers that local motion is more perfect on account of the perfection of the movable thing, in which according to it the least variation occurs. For it is manifest that this reply tends to this, that local motion is not formally and simpliciter more perfect, but only secundum quid and materially. On this account, in VIII Physics, in the exposition of text 59, ²⁵ formulating the argument of Aristotle, he says: The less a motion takes away from the movable thing, the more perfect is its subject, and thus the motion itself is also more perfect in a certain way. Local motion is of this kind. Therefore, etc. For from these things it is clear that he means that local mutation is not formally and simpliciter more perfect than the others, but secundum quid and materially, since he proposes that the motion which takes away less from the subject has a more perfect subject, and from this it is more perfect in a certain way.

3. To the argument for the other opinion, ²⁶ indeed, it is said that it is based on something false, namely that motion is nothing other than the privation of the term. For this is entirely false. For motion is not formally a privation, but the act of a subject deprived of the term of motion, and tending through motion toward it.

VIII. But concerning this determination a twofold doubt occurs. The first is: The motion of the first movable thing is the measure of all other motions, as is clear from X Metaphysics, text 4. ²⁷ But each thing is measured by the first and most perfect of its genus. Therefore such a motion is according to its proper nature prior and more perfect than other motions, and not only materially, by reason of the subject. Therefore, etc.

The second is: St. Thomas proves, both here and in very many other places, that all bodily motions are traced back to the motion of the heavenly bodies as to a cause, because local motion is prior to the others in time, nature, and perfection. ²⁸ But to be the cause of the others seems to belong to it from its own proper nature, since the heavenly body has from it that it is the cause of other motions; for, according to St. Thomas, if the motion of the heaven ceases, all other natural motions will cease. ²⁹ Therefore, etc.

2. To the first it is answered that a twofold quantity can be considered in motion, according to which to be measured can be attributed to it. One is the essential and quidditative quantity, according to which it holds a determinate grade in the genus of beings and in the genus of motion. The other is the quantity of speed and slowness, namely inasmuch as in a greater or lesser time so much of space is traversed, according to which it is said to hold a determinate grade in speed. If we speak of motion as to its first quantity, thus it is not true that all other motions are measured by local mutation, but the generation of all of them is the measure; for which mutation is formally and quidditatively more perfect or more imperfect is known from the fact that it approaches more or less to the perfection of generation. — If, however, we speak of motion as to its other quantity, thus all other motions are measured by the local motion of the first movable thing, namely as by the swiftest and simplest motion. But that perfection does not belong to it from the absolute nature of local motion, but from the fact that it is the motion of the first movable thing, to which it belongs to be moved most swiftly and simply. Therefore it does not follow that from its formal nature it is more perfect than the others, but only materially and from the subject.

3. To the second it is likewise said that it belongs to the motion of a heavenly body to be the cause of the others, not from the formal nature of motion, but from the perfection of the subject. For because it requires a subject in potency only to place (ubi), and not to another intrinsic absolute form, therefore it alone can belong to the first heavenly body, which by its motion is the cause of all other motions. Hence the assumed minor is false. — For the proof of which, it is said that the heavenly body does not have from motion that it is the cause of other motions as from a form through which it acts, but as from a disposition necessary to it for moving, because it is proper to a body that it does not act by an action appropriate to it inasmuch as it is a body, unless it is moved. And on this account, when motion ceases, that action of the heavenly body ceases.

IX. To the second doubt ³⁰ it is said that St. Thomas does not say that the whole motion is a middle absolutely, but as it were a middle: because, namely, it is not properly a middle, in that it has neither a beginning nor an end in the magnitude that is traversed, as was argued; but it has a certain likeness of a middle, inasmuch as it is something extended. For just as the extended in a line, which is between the indivisibles at which the line is terminated, is a middle between them, so the whole circular motion is considered as a certain extension of motion, and therefore has a certain likeness of a middle. Yet it falls short of the proper nature of a middle, inasmuch as there is not in it to take two extremes in act by which it is terminated, just as also in a circle there are no such two extremes.

2. To the third doubt ³¹ it is said that, although circular motion does not have a beginning and an end in comparison to the magnitude over which the motion occurs, it nevertheless has a beginning and an end of duration, according as it is divided by the division of time; for there is some instant from which the circular body begins to be moved, and some instant at which its motion is terminated. Therefore it does not follow that every circular motion is perpetual.

3. To the fourth doubt ³² it is said, according to the mind of Aristotle in VIII Physics, ³³ that circular motion can be said to be always in the beginning, in the middle, and in the end: because on a circular magnitude any point can be taken as a beginning and as a middle and as an end, in that there is no point on such a line that is in act a beginning or an end. But according to our designation, some part of the movable thing can be designated, and in the containing place some point corresponding to the beginning of that part can be designated; and thus one can say that the movable thing begins to be moved from such a designated point of the magnitude; and that designated point will be the beginning from which motion begins according to our designation, not according to reality. When, therefore, it is said here that circular motion has neither a beginning nor an end, it is understood according to reality: inasmuch as that which is moved circularly always remains in the same real place according to reality, and there is not on the part of the magnitude any beginning or any end in act. But that which is said, that it is always in the end, in I Meteorology, is understood with respect to our potential designation, according to which we can take any point of the magnitude as a beginning and as an end of the motion of some part of the movable thing.

X. Seventh. ³⁴ Heavenly bodies alone among corporeal things are unalterable, namely by corruptive alteration. Therefore they are the cause of all alteration. Therefore they are the cause of all motion in these lower things.

The first consequence is proved. Because as the simply immobile is related to motion simply, so that which is immobile according to this motion is related to such a motion: when, namely, to move belongs to such an immobile thing. But the simply immobile is the cause of all motion.

The second consequence, however, is proved. Because alteration in these lower things is the cause of all motion: since through it one arrives at increase and generation; but the generating thing is the per se mover in the motion of heavy and light things.

2. Note that the motions of lower things can be compared in two ways: in one way, in relation to one and the same thing; in another way, in relation to diverse things. — In relation to one and the same thing, they can also be considered in two ways: in one way, according as they are attributed to it as to a cause; in another way, according as they are attributed to it as to a movable thing.

If they are considered according as they are attributed to one thing in the character of the cause of the other, thus the generator of heavy things has this order: that first it alters the matter from which the heavy thing must be generated; secondly, it generates the heavy thing; thirdly, it gives local motion. And thus alteration precedes the other motions. — If, however, they are attributed to one thing in the character of a movable thing, so that it is one and the same movable thing for all those motions, generation precedes all other motions. For all motions, namely of alteration and of increase and local motion, presuppose their subject in act; but this occurs through generation.

If, however, these motions are considered in diverse movable things, thus local motion precedes alteration: because something cannot be altered anew unless the altering and the altered thing become near, which does not occur without the local motion of either the altering or the altered thing. Alteration, however, precedes generation: because something cannot be generated unless first the proper matter, from which it must be generated, is disposed through alteration. But the other motions follow generation.

Therefore the order of motions assigned here in these lower things, which is according to the mind of Aristotle in VIII Physics, ³⁵ is understood according as they are considered in movable things.