Commentaria in Summam contra Gentiles, Liber III

Furthermore, in order that it may become more evident that our will does not suffer necessity from celestial bodies, St. Thomas wishes to show that not only can they not inflict necessity upon human choice, but also that not even bodily effects proceed with necessity from them in these lower realms ¹. Regarding this, however, he does two things ²: first, he shows the proposition; second, he answers a certain argument of Avicenna ³.

I. As to the first, he argues first as follows. These lower things are mutable, and not always in the same state: on account of matter, which is in potency to many forms; and on account of the contrariety of forms and powers. Therefore, the impressions of celestial bodies are not received in these things by way of necessity. — The consequence is proved. Because the impressions of natural causes ⁴ are received in effects according to the mode of the recipients.

Secondly. Celestial bodies are remote causes of lower effects: the proximate causes, however, are the active and passive powers in these lower things, which are contingent causes, since they can fail for the most part. Therefore etc.

— The consequence is proved. Because an effect does not follow from a remote cause of necessity unless the intermediate cause is also necessary. This is illustrated by a likeness in syllogisms, in which, when the minor premise is contingent, nothing follows except a contingent conclusion, even though the major premise is necessary.

Note that by the effects proceeding in these lower realms St. Thomas intends all those particular effects that occur in the sublunary region. The first argument proceeds concerning all of these: whether, I say, they are posited to proceed immediately from the heaven, or by the mediation of particular causes. But this second argument proves concerning those effects alone that proceed from the heaven through the mediation of lower powers.

Thirdly. If it were so, then things in the lower realms would always be in the same state. This is false. Therefore etc. — The assumption is proved. Because the motion of celestial bodies is always in the same way.

Note that this argument is founded upon this manifest proposition: An effect proceeding of necessity from a cause that is always in the same state, always happens in the same way.

Fourthly. The individual things that occur in these lower realms from the impression of celestial bodies are contingent: since any one of them can be impeded. Therefore the connection of those things that happen in lower realms from the impression of the heavens is not necessary. — The consequence is proved. Because one necessary thing cannot be made from many contingent things: since all can fail together just as any of the contingent things can.

Note that this argument directly concludes against those who say that the connection of the things that occur here by the impression of celestial bodies is necessary, although some happen contingently.

Fifthly. That which matter requires is not removed by the action of celestial bodies: since celestial bodies are natural agents, which require matter upon which they may act. But the matter upon which celestial bodies act consists of lower bodies corruptible by nature, which just as they can fail in being, so can fail in acting: and consequently they do not produce effects of necessity. Therefore etc.

II. Note that this argument differs from the first and the second. Because, since lower bodies can be compared to higher ones both as matter alone, and as a second and instrumental agent to the principal agent, we can consider lower bodies in three ways. First, as having the character of matter alone, upon which celestial bodies act. And according to this consideration the first argument proceeds. — Secondly, as having the character of a proximate agent alone, in relation to celestial effects produced through their mediation. And according to this the second argument proceeds. — Thirdly, as having simultaneously both the character of matter and the character of a secondary and instrumental agent in relation to the heaven itself. And according to this, this fifth argument proceeds. For it is concluded that the effects of the heavens do not occur in these lower realms of necessity, because, since lower things can fail in acting according to the nature of their own condition, the impression of celestial bodies does not remove this from them. For an agent does not remove from the matter upon which it acts, and which it uses as an instrument, that which is due to the matter itself, and which is presupposed in the matter: but, presupposing its condition, it uses it for its effect. For although an agent sometimes removes preexisting dispositions from the matter which it uses simply as matter, and introduces new dispositions, as is evident in generation, namely because they are incompatible with the form to be introduced; nevertheless, from the matter upon which it acts as an instrument which it uses for its effect, it does not remove its natural dispositions, which it presupposes as dispositions of the matter, and not as the terminus a quo of its action or motion.

III. To these arguments it could perhaps be said, as Albumasar, at the beginning of his Introductorium, strives to defend the possible, that it is necessary that the effects of celestial bodies be completed, yet possibility is not thereby taken away from lower bodies: because every effect is in potency before it is produced, but when it is already in act, it passes into necessity; and thus it is not excluded that the effect is at some time possible, although it is necessary that that effect be produced at some time.

But, says St. Thomas, the possible cannot be defended in this way. Which is shown. Because, since the possible is twofold, namely, one that follows upon the necessary, and another that is opposed to the necessary; it is not necessary to defend the first, because effects are not said to be caused of necessity in opposition to this; but the second. Moreover, something is not said to be possible or contingent in this way solely because it is sometimes in potency and sometimes in act: because thus the possible and contingent would also be found in celestial motions. But the possible taken in this way has this in its definition, that it is not necessary for it to be produced when it is not: namely, because it does not follow of necessity from its cause. This is illustrated in the contingent sitting of Socrates, and in his necessary death. Therefore, if it follows of necessity from celestial motions that their effects will at some time be in the future, the possible and contingent which is opposed to the necessary is removed.

2. For the clarity of this refutation, it must be considered that, according to this response, the possible is taken in two ways. In one way, as it is opposed to the impossible. And thus that is called possible which is not impossible to be, or to which to be is not repugnant. And because not only the contingent, but also the necessary is not impossible to be — otherwise, as St. Thomas deduces, necessary to be would be necessary not to be, since impossible to be is necessary not to be — on that account he says that such a possible follows upon the necessary; just as, namely, the more universal follows upon the less universal, as animal upon man. — In another way the possible is taken as it is opposed to the necessary. And then the possible is the same as the contingent, namely that which can be and not be, just as the necessary cannot not be.

If, therefore, the effects of celestial bodies occur of necessity, namely because they cannot not occur, it follows that they are not contingent to occur and not to occur; and thus, that they are not possible with the possibility opposed to the necessary. Therefore, those positing that the effects of the heaven occur necessarily cannot preserve the possible that is opposed to the necessary.

IV. As to the second ⁵, the argument of Avicenna is adduced, in the tenth book of his Metaphysics, chapter 1, to prove that the effects of celestial bodies occur of necessity. For he argued: If the effect of celestial bodies is impeded, this occurs through either a natural or a voluntary cause. But every such cause is reduced to some celestial principle. Therefore that impediment proceeds from certain celestial principles. Therefore, if the entire order of celestial bodies is taken together, it is impossible that its effect should ever be thwarted.

St. Thomas says that this argument was also used by certain Natural philosophers who denied chance and fortune, on the grounds that, according to them, of every effect there is some determinate cause; but when the cause is posited, the effect is posited of necessity.

2. He answers, however, according to the mind of Aristotle in VI Metaph., text 7: and he says first, that this proposition is false, Whatever cause is posited, it is necessary that its effect be posited. Because the proper and per se sufficient cause of some effect can be impeded by the concurrence of another cause, so that the effect does not follow.

He says secondly, that the other proposition is also false, Everything that is in any way whatever, has a per se cause. For it is not true of those things that are per accidens, but only of those that are per se. He illustrates this in the white and the musical, which are not together through any cause, since they have no order to one another: but whatever things are together through some cause have an order from that cause.

He says thirdly, in responding to the argument of Avicenna, that, given some effect, we will say that it had some cause from which it did not follow of necessity, because it was able to be impeded by some cause concurring per accidens. And although it were possible to reduce that concurring cause to some higher cause, yet the concurrence itself that impeded cannot be reduced to any cause. And thus it is false that the impediment of this effect proceeds from some celestial principle.

As to the third point ⁶, the conclusion is confirmed by the authority of Damascene, in the second book; by the authority of Aristotle, in II de Somno et Vigilia; and by the authority of Ptolemy, in the Quadripartitum and Centiloquium.

V. For the clarity of the response to the argument of Avicenna and of the ancient philosophers, it must be considered first, with respect to that proposition, some cause, although it be the per se and proper sufficient cause of some effect, can nevertheless be impeded, that a cause is called sufficient when it has such great power from its own form that, no other cause of its order concurring, it can produce the effect: just as fire is the sufficient cause of heating; for it can heat by itself alone, no other particular effective cause concurring. By contrast, an insufficient cause is called that which does not have such great power from its own form that by itself alone, no other cause of its order concurring, it can produce the effect: just as, when many drag a ship together, which none of them could drag per se, each one of them is called an insufficient cause of that pulling. Moreover, it is not unfitting that some cause have as much power as is required for the production of some effect, and yet be impeded from the production of that effect: just as fire can be impeded from the heating of something, say wood, by something vehemently cold either diminishing its power and heat, or introducing some contrary disposition into the wood. Whence this consequence is not valid: This cause, on account of some supervening impediment, does not produce this effect; therefore it is not a sufficient cause of that effect: for it can be impeded, and yet in itself be sufficient. The sign of this is that, with the impediments removed, no other cause of its order assisting, it would produce that effect. For from this it is proven to have as much power as the production of that effect demands. Whence, when it is said that a cause is that upon which an effect follows of necessity, it is understood of a sufficient cause not impeded. Therefore it was very well said by Aristotle and St. Thomas that it is not true that, whatever cause is posited, it is necessary that the effect be posited; and that there can be some proper and sufficient cause of some effect, which nevertheless, on account of some supervening impediment, will not achieve its effect.

2. It must be considered secondly, concerning this proposition, An effect per accidens does not have a per se cause, that an effect per accidens can be considered in two ways: in one way, absolutely and in itself, insofar as it is a being; in another way, insofar as it is an effect per accidens. If it is considered in the second way, thus it is manifest that it does not have a per se cause: for to whatever cause it is compared as an effect per accidens, it is evident that that cause is not its per se cause, although it were the per se cause of something else; for causes must proportionally correspond to effects, as is held in II Phys.⁷, namely so that a per se cause corresponds to a per se effect, but a cause per accidens corresponds to an effect per accidens. — If, however, it is considered in the first way, thus it is not unfitting that an effect per accidens have some per se cause in some way. For since an effect per accidens cannot be reduced to a per se cause insofar as it is such, as is said in the Prima Pars, q. 115, a. 6, and at the end of the first book of Perihermenias ⁸, by St. Thomas, because it is not truly a being, since it is not truly one; yet if it happens that some effect which in itself, and in relation to proximate causes, is not truly one, because it includes two things having no order between themselves from their own natures, has some unity and some order in comparison to some cause, it is not unfitting for that effect to have a per se cause; because such an effect, although in comparison to some causes it is an effect per accidens, nevertheless in comparison to another cause it will be a per se effect. Just as the meeting of two servants, in itself, and compared to the particular causes of both, is a being per accidens: because the motion of one servant has in itself no order to the motion of the other; likewise the finding of the fellow servant along with the walking of the servant has no order, and no unity according to its own nature, nor according to its proper cause. Therefore a meeting of this kind, if it is referred to the motive power of both, or to their intention, does not have a per se cause, but only a cause per accidens: since the motive power or intention of the one does not have efficacy over the motion and intention of the other. If, however, the meeting of these servants is considered in comparison to the master sending them so that they might meet and cross each other's path, then these motions and the finding of the fellow servant along with the motion have some unity of order from the intention of the master sending and ordering one motion with the other, and the motion of the one to the finding of the fellow servant. And therefore, as such, such a meeting is a per se effect, and has a per se cause. When, therefore, it is said that an effect per accidens does not have a per se cause, it is understood of it insofar as it is an effect per accidens and insofar as it is a being per accidens: but not insofar as it is in some way a per se being and a per se effect.

3. It must be considered thirdly that, although every effect per accidens in these lower realms, except the evil of fault, is referred to God as to a per se cause, because with respect to Him they are per se effects, both ordered and intended; and some are also referred as to a per se cause to the power of a celestial body: nevertheless, not all effects of this kind are reduced to celestial power as to a per se cause, but rather some are also found to be per accidens compared to a celestial body. For since an effect that happens outside the intention of some cause is from it per accidens; and the intention of a cause is nothing other than its inclination to the production of the effect: whatever happens outside the inclination of a cause, whether it be something positive or something privative, happens per accidens from such a cause. Because, therefore, the heaven is an acting cause in these lower things for the most part, and sometimes failing, namely in the fewer instances; if it is inclined, for example, to stir up a storm, and a storm does not occur but rather clear weather, from the concurrence of some impeding cause: both the clear weather itself, and the non-occurrence of the storm, are said to be per accidens in relation to the influx of the heaven, because it is outside its intention and inclination. Likewise, if by acting upon the body it inclines the soul of a man to something, and the will, which is not directly subject to the celestial body, chooses the contrary: that which is done voluntarily is said in relation to the heaven to occur per accidens, because it occurs outside its inclination and outside its intention.

4. From these things it is clear that what St. Thomas says in responding to the argument of Avicenna is true: namely, that it is not necessary that all celestial effects occur of necessity on the grounds that every effect must be reduced to some per se cause, because the effect was able to be impeded from occurring by some cause concurring per accidens; and that, although it happens that that impeding cause is reduced to some celestial principle, yet it does not impede such an effect except by reason of its concurrence with the power and inclination of the cause toward such an effect, which concurrence is per accidens; for it happens to this cause, according as at this time it is inclined to the production of this effect, that there is at the same time another cause which at that same time acts in a way that is impeditive of its effect. Such a concurrence per accidens, however, does not have any natural per se cause, but only per accidens: although the concurring cause, which happens to impede, has in itself some cause.

VI. But against the aforesaid two doubts arise. The first is, because it seems that such a concurrence of diverse causes has a per se cause: contrary to what is said here. For the concurring cause that impedes does not act except by the power of the heaven: since all lower causes act in the power of a higher. Likewise, the cause that was disposed toward the production of its effect was inclined to its effect by the power of the heaven. Therefore both particular causes were simultaneously moved to their effect by one cause, namely celestial power. Therefore their concurrence was per se intended by the heaven.

The last consequence is proved. Because St. Thomas says, in VI Metaph.⁹, that the blooming of this herb or of that, if it is referred to the particular power that is in this plant or in that, seems to have no order to the blooming of the other: on the contrary, it seems per accidens that, while this herb blooms, that one blooms, because the cause of the blooming of the one is not the cause of the blooming of the other. If, however, it is referred to the power of a celestial body, which is a common cause, the concurrence of these bloomings is found not to be per accidens, but to be ordered by some first cause, which simultaneously moves both herbs to blooming. For from these things it is clear that, where concurring causes are simultaneously moved by the same cause, such a concurrence is not per accidens. And consequently, if diverse particular causes are simultaneously inclined to operation by the heaven, it follows that their concurrence will not be per accidens, but per se intended.

From this it further follows that nothing is per accidens in these lower realms in relation to the power of the heaven: since all concurring causes, of which one impedes the other, are moved by the power of the heaven.

2. The second doubt is¹⁰, because St. Thomas does not seem to assign here any other reason why it is not necessary to reduce every effect to a per se cause, except because an effect per accidens has as its cause the concurrence of diverse acting causes, of which one impedes the other, of which concurrence there is no per se cause. But against this seems to be his statement in VI Metaph.¹¹, where he posits that an effect of a celestial body can per accidens not occur on account of the indisposition of the matter. Therefore not every event per accidens has as its cause the concurrence of diverse acting causes.

VII. For the clarification of the first doubt, it must be considered that, although the heaven is the universal cause of all natural effects in these lower things, there are nevertheless in the heaven diverse powers, and diverse influences of diverse stars and diverse constellations; which powers, indeed, although they are ordered among themselves if considered in themselves, yet, according to the way they issue into operation and are terminated at their effects, seem to have no per se order, since one power does not extend itself to the effect of another. For just as all the powers of the soul are ordered in themselves, insofar as they originate from its essence by the intention and inclination of the soul—and therefore their concurrence in the one essence of the soul is per se, and intended by the soul, and by God creating the soul—yet many of them, with respect to actual operation, have no per se order, but the concurrence of their operations is per accidens, just as the fact that, while sight sees something, taste perceives something sweet, is per accidens, since neither is the action of sight required for the action of taste, nor conversely: so all the powers of the heaven are indeed ordered insofar as God, who is their immediate cause, appointed their order, yet the concurrence of the actual operation of one with the actual operation of another, or the effect of one with the effect of another, can be per accidens; just as it is per accidens that, while one star moves some matter to coldness, another star at that time moves another matter or the same matter to heat, if regard is had to the particular powers themselves. Whence it happens that, if diverse causes are moved to act by one heavenly power, the concurrence of those causes in acting is per se in order to the heavenly power, because it is according to the inclination and intention of one power moving both causes to operation at the same time; but if diverse particular causes are moved to their effects at the same time by diverse heavenly powers that are not subordinate, the concurrence of those causes in acting is per accidens, even when related to the heavenly powers, because they are not moved to act from the intention of one power, but from the intention of diverse powers not having an order among themselves with respect to their actual operations and their effects, and consequently not intending any unity between the operations and the effects.

2. It is said, therefore, that the mind of St. Thomas in this place is that the concurrence of acting causes does not always have a heavenly power as its per se cause, because they are not always moved to their proper actions by the same heavenly power. But in the sixth book of the Metaphysics he maintains that it sometimes has a heavenly power as its per se cause, because they are moved to act by one and the same heavenly power, just as two plants are sometimes moved to flowering by one heavenly power. Because, however, the concurrence of a cause disposed and ordered to the production of some effect with a cause hindering that effect from happening does not arise from one heavenly power moving both causes to operate, but from diverse powers, of which one moves one to the production of one effect, while the other moves the other to an action hindering the action of the other; therefore the concurrence of those causes, of which one hinders the other, is not per se, even when related to the heavenly power. And because St. Thomas is speaking here of such a concurrence by which a cause is hindered from its effect, he therefore says absolutely that it is per accidens, and does not have any heavenly principle as its per se cause. But in the sixth book of the Metaphysics he speaks of the concurrence of causes universally: namely, whether it is a concurrence of mutually hindering causes, or of causes not hindering one another. Therefore he did not say absolutely that their concurrence does not have a heavenly cause, but he said that some concurrence, namely of causes not hindering one another, can have a heavenly power as its per se cause.

To the argument, therefore, the first consequence is denied. Because although in mutually hindering causes each of the causes is inclined to its actions by a heavenly power, yet they are not moved by one heavenly power, but by diverse ones. And therefore the concurrence of those particular causes is per accidens, even when compared to the power of the heaven.

3. But if it should be urged that, although these causes, of which one hinders the other, are referred to diverse heavenly powers, yet it is necessary to refer them finally to the first motion of the heaven, which is one; and thus their concurrence will have the motion of the heaven itself as its per se cause: — it is said that the motion of the heaven does not act on these lower things per se, but by means of the powers of the heavens and of the stars. Therefore, as it moves these lower causes, it does not have the character of one cause, but of many, by reason of the diverse powers by which it moves, although in itself it is one. For this reason it is not necessary that the concurrence of these causes, on account of the unity of the heavenly motion, have a per se cause.

4. If it should likewise be urged that all the particular powers of the stars depend on the universal power of the first sphere flowing into these lower things, for every lower cause acts in the power of a higher cause; and thus every concurrence of lower agents depends on one power; and consequently is per se: — it is answered that that universal power can be considered in two ways: in one way, in its universality absolutely, as it is in the first sphere itself; in another way, as it is limited in some lower power and determined to some particular effect. If the concurrence of lower agents is compared to the universal power itself taken in the first way, in this way it is certainly conceded that every concurrence of lower natural causes is per se, and none is per accidens: on the ground that every lower acting power is moved at the same time to act by a numerically one cause. But if it is referred to it taken in the second way, the concurrence can be per accidens with respect to some power. For in this way some lower agents, mutually hindering each other, are not referred to that power as it is one, but as it is multiplied and variously limited in lower things; and it happens accidentally to it thus limited that, while it moves one of the particular causes to this particular effect, limited in another way it moves at the same time to another effect; and therefore it is outside its intention that some hindering cause should act at the same time.

Therefore the statement of St. Thomas is not understood in the first way, but in the second. For even when it is said that some natural effect in these lower things happens per accidens in order to a heavenly power,¹² this is not to be taken in the first sense, as if, namely, some natural effect could happen outside the inclination of all the heavenly powers, or of that first universal power taken in its universality; but it is to be taken in the second sense. For it is not unfitting that the effect to which this particular heavenly power—or even that universal power limited in this particular power—inclines does not happen in these lower things, but another happens, on account of other causes, outside its intention and inclination.

VIII. To the second doubt¹³ it is answered: and it is said first, assuming that St. Thomas is speaking of the concurrence of an acting cause that hinders, that we can speak of the effect of a heavenly body in two ways: namely, either of that which it produces by means of some particular cause able to fail; or of that which it produces per se and immediately. If we speak of that which it can produce by means of some defectible cause, in this way it can be that the effect does not follow, on account of some efficient cause hindering the action of the other cause as it goes forth from it. — But if we speak of that which it produces immediately, in this way it cannot be hindered through the action of any acting cause that hinders the action itself as it goes forth from the agent: since a heavenly power cannot be weakened or altered. But it can be hindered on the part of the matter. Because, since a heavenly power acts only through motion, and is finite and limited, it requires matter that is disposed and determined for the reception of the heavenly influx. Now it happens sometimes that the matter is not disposed for the reception of such an influx, either on account of its thickness, or on account of coldness or heat, or something of this kind, whether that indisposition be from nature or caused by some extrinsic agent. And then, on account of the concurrence of such indisposed matter with the power of the heaven, it happens per accidens that the heavenly effect does not follow. Therefore, what is said in VI Metaphysicae does not contradict what is said here: because there St. Thomas is speaking of an effect of which the heaven alone is the cause; but here he is speaking of an effect of the heaven by means of a contingent producible cause.

It is said secondly, that from the words of St. Thomas it is not gathered that he is speaking here only of the concurrence of an acting cause hindering the action of another as it goes forth from the agent: but he is speaking indifferently of concurrence, whether it be a concurrence per accidens of an acting cause hindering the action as it goes forth from the agent; or a concurrence of an acting cause hindering by making the matter indisposed; or a concurrence only of the matter itself indisposed from its own nature. For in every concurrence of this kind it is true that, although the hindering cause considered in itself can be referred to some heavenly principle, yet not every concurrence has a heavenly power as its per se cause, but there is some concurrence which, since it is per accidens, cannot be referred to one heavenly cause.

IX. Lastly, it should be observed that this determination of St. Thomas, namely that heavenly bodies do not act of necessity in these lower things, does not contradict what has been said above many times, namely that the motion of the heaven, or that the heaven is a necessary cause. For that is understood, as he says in VI Metaph.,¹⁴ in the sense that heavenly bodies, and their motions and actions, as far as is in them, have necessity: because, namely, neither are the bodies themselves corruptible or alterable; nor, as far as depends on them, can they not act. But it is not repugnant to this that their effects can fail on account of the indisposition of the matter, or on account of the contingency or freedom of secondary causes.