Commentaria in Summam contra Gentiles, Liber III

After St. Thomas determined concerning divine providence according as it extends commonly to all things, he now begins to treat of it according as it particularly extends to human beings ¹. Concerning this, however, he does two things: first, he shows by what things human choices are governed; second, he infers certain corollaries, chap. XCI. — Concerning the first he does three things: first, he shows that the heavenly bodies are not the cause of human choices; second, that neither are separated substances, chap. LXXXVIII; third, that they are subject to divine providence, chap. XC.

Concerning the first he does two things: first, he shows that the heavenly bodies do not make impressions upon our intellects; second, that they are not the cause of our choices, in the following chapter.

I. As to the first, two conclusions are posited ². The first is: Of those things which pertain to the intellect, the heavenly bodies cannot be directly the per se cause.

It is proved first thus. The intellect in the order of nature surpasses all bodies. Therefore it is impossible for the heavenly bodies to act directly upon the intellect. Therefore they cannot be the per se cause of those things which pertain to the intellect. — The consequence is proved. Because the order of divine providence is that inferior things are ruled and moved by superior things.

2. For the evidence of this reason, it must be considered that, on the part of the effect, that is called the per se cause of some effect which by its own power and its own action attains the effect according to itself, not by reason of something else to which it is conjoined. But that is said to be an accidental cause which does not attain the effect according to itself by its own action, but something else, to which it is conjoined. Just as we say that one who digs a grave is the per se cause of the grave; but of the finding of a treasure he is an accidental cause.

It must be considered secondly, that it happens that one thing acts upon another in two ways: in one way, directly; in another way, indirectly. Something is said to act directly upon another when its action and influx reaches it as a patient, causing something in it. But it is said to act indirectly when its action does not reach it by causing something in it, but reaches something else from which something results in it. In the first way, we say that fire acts upon the water which it heats; in the second way, we say that it acts upon men between whom discord has arisen from the receipt of hot water.

It must be considered thirdly, that acting directly upon some patient is necessarily inferred from this, which is to be the per se cause of that which comes to be in such a patient: for an agent cannot be the per se cause of something made in something unless it acts directly upon the subject and patient; for what is caused by an agent in something must come to be through some action of the agent terminated at the patient as at a subject. But to act per se is not inferred from this, which is directly: because even an accidental agent can act directly, inasmuch as by its action it attains something, though not primarily, but through another. Also, to act upon a patient indirectly is necessarily inferred from this, which is to be an accidental cause of that which comes to be in the patient. And because, when some consequent necessarily follows from some antecedent, the negation of the antecedent is also necessarily inferred by the negation of the consequent, therefore St. Thomas, from the fact that the heavenly bodies do not act directly upon our intellect, infers that they are not the per se cause of those things which come to be in the intellect: for they neither cause per se those things which come to be in the intellect, nor does their action attain the intellect.

II. Secondly. Those things which pertain to the intellect are altogether outside motion, per se speaking, as is clear in VII Phys.: indeed, through rest from motion the soul becomes prudent and knowing. Therefore etc. — The consequence is proved. Because, since nothing is caused by motion except inasmuch as the agent moves and the patient is moved, those things which are immobile, as being altogether outside motion, are not caused by motion. But a body does not act except through motion.

Note that St. Thomas adds to the antecedent per se speaking: because those things which come to be in the intellect can be in motion per accidens, by reason of the phantasms concurring toward intellection.

Thirdly. The intellect is neither a body nor a corporeal power. Therefore the heavenly bodies cannot directly make an impression upon it. — The consequence is proved. Because, since nothing is caused by a body except inasmuch as, while it is moved, it moves, that which receives the impression of a body must be moved: but nothing is moved except a body.

Fourthly. Every agent and mover must be in some way in act with respect to those things which it causes. But heavenly bodies are not intelligibles in act: since they are sensible singulars. Therefore they cannot cause intelligibles. Therefore etc. — The major premise is proved. Because everything that is moved by something is reduced by it from potency to act. But nothing is reduced to act except by that which is in act. — But the last consequence is proved. Because our intellect is not in potency except to intelligibles in act: namely, as to forms to be received immediately in itself.

This reason proves in particular that the heaven is not the cause of the intelligible species.

III. Fifthly. What is subject to a heavenly body according to its operation is also subject to it according to the principle of its nature. But the intellective part is not caused by any corporeal principles, but is entirely from without. Therefore its operation is not subject to heavenly bodies. — The major is proved. Because the proper operation of a thing follows the nature of the thing itself, which is acquired for generated things through generation together with the proper operation. It is shown in the heavy and the light.

2. Concerning this reason a twofold doubt occurs. The first is because, if nothing can be subject according to operation to a body which is not caused by it according to its substance, it follows that man could not be the cause of the operation of some instrument of which he is not the cause. Which nevertheless seems manifestly false: for he is the cause of the cutting of the sword, and yet he is not its cause.

The second is because, although the major is true of an action following nature necessarily at once unless it is impeded, yet it does not follow that the cause of intellection is also the cause of the intellective nature: because intellection is not such an operation, as is clear.

3. To the first it is said, first, that the reasoning proceeds concerning the operation following nature per se, but not concerning the operation of an instrument, which does not belong to the instrument except through a new motion by which it is moved by something. For the action of an instrument is attributed rather to the one using the instrument than to the instrument itself: for we say rather that the man cuts the wood than that the sword does.

To the second it is said that this reason seems to conclude concerning the action of the agent intellect, which is to make intelligibles in act, or to actuate the possible intellect. For just as in the preceding reason he showed that the heavenly body is not the cause of the intelligible species, so by this reason it is shown that it is not the cause of that action by which the agent intellect forms the intelligible species themselves. Therefore the assumed proposition very well infers the proposition at hand. Because this operation of the agent intellect naturally follows the agent intellect, when fitting phantasms are posited in the imagination and duly disposed, just as heating naturally follows fire. On that account, just as the generator of fire, who is the cause of heating, is also the cause of the nature of fire; so also what is the cause of the operation of the agent intellect must be the cause of its nature.

IV. Sixthly. The intellect in its operation abstracts from time, just as from place³: since it considers the universal, which is abstracted from here and now. Therefore etc. — The consequence is proved. Because those things which are caused by heavenly motions are subject to time, which is the number of the first motion.

It must be observed first, that St. Thomas suitably argues from the understood object, inasmuch as it is such, that the operation of the intellect is not in time. Because, since being abstracted from place and time does not belong to the universal according as it is in the singular—indeed, as such, it is determined to a definite time and to a definite place—but it has separation from these conditions according as it is the object of the intellect: it is necessary that intellection itself, which is specified by the understood object inasmuch as it is understood, be outside time; for the nature of a thing must be determined by the specifying form to its mode of being.

It must be observed secondly that, although the operation of the intellect is not in time per se, yet time is mixed with it per accidens, by reason of the phantasms, which are required for it, as has been shown in the preceding⁴ according to the mind of St. Thomas: just as also the universal itself, which per se abstracts from place and time negatively, yet by reason of the singular in which it is, is determined to a definite place and a definite time.

V. Seventhly. Understanding transcends the species and form of any agent body. Therefore no body can understand through its corporeal form. Therefore much less can it cause understanding itself in another. — The first consequence is proved. Because nothing acts beyond its species: namely, as a primary and per se agent. — But the antecedent is proved. Because a corporeal form is material and individuated; but understanding has its species from the object, which is universal and immaterial.

2. Concerning the last consequence a doubt occurs. For there are many things which an agent cannot cause in itself, and yet causes in another: for the sun causes forms in these inferior things, which nevertheless it does not cause in itself. Although therefore something does not cause in itself the operation of understanding, yet it does not follow that it cannot cause it in another.

It is answered that this consequence holds concerning the act of understanding inasmuch as it exceeds the form of the agent. For if a body cannot cause intellection in itself on account of its excess above the form and species of the body, much more will it not be able, on account of the same reason, to cause it in another: for it would seem more likely, if it had causality over such an act, that it would cause it in itself than in another, from the fact that it is an immanent operation. But if it cannot do this, much less will it be able to do the other. That consequence therefore does not hold in virtue of that proposition, 'An agent which cannot cause something in itself, neither can cause it in another,' as the objection assumes; but in virtue of this one: 'What cannot cause intellection in itself, on account of the excess of intellection itself above its form and species, much less can cause it in another.' But this latter is manifestly most true. For that reason St. Thomas did not take care to prove that consequence, as being per se manifest.

VI. Eighthly. Our soul understands according as it is united to intellectual substances, which are superior in the order of nature to the heavenly bodies. Therefore etc. — The antecedent is proved. Because the soul cannot understand except according as it obtains the intellectual light from there. — But the consequence is proved. Because according to that by which something is united to superiors, it is not subject to inferiors.

For the evidence of this reason, it must be considered that that by which something is united to superiors, as if through a certain continuation, since it is a certain participation in the superior, seems to pertain to the nature of the superior, although it is found in an all the more excellent mode in that superior. Whence from the superior and the inferior, as to that, in a certain way one thing is made: or at least between them there is such an immediacy that nothing worthier can mediate between them. And for that reason what is inferior to that superior is also inferior in the order of nature to that which is thus continued to that superior. And consequently, just as it cannot act upon the superior nature, so it cannot act upon that which is continued to it, as to that in which they are united. Since therefore, by reason of the intellectual light, there is a certain continuation between the human soul and superior intellects, and the intellectual operation proceeds from such a light: it very well follows that the heavenly bodies, which are inferior to intellectual substances, cannot act directly upon the human intellect, just as neither can they upon superior intellects. And according to this does this reason proceed.

VII. Ninthly. And it is a reason directly against the position of the philosophers. To posit that the heavenly bodies are the cause of our understanding is a consequent of the opinion of those who posited that the intellect does not differ from sense: as is clear from the Philosopher, II De Anima, text 150⁵. But this opinion is false. Therefore etc.

For the manifestation of the major premise he introduces first the opinion of Democritus, Empedocles, and other ancient Natural Philosophers, who, positing that the intellect does not differ from sense, said that, since the transmutation of inferior bodies follows the transmutation of superior bodies, the intellectual operation also will follow the motions of the heavenly bodies. — It is manifested by the authority of Homer, expounded by Augustine, IV City of God, chap. XI, saying that such is the intellect in earthly gods and men, as the Father of men and of gods brings on⁶ in a day.

He introduces secondly the opinion of the Stoics, who posited that the life of men is led by a certain fatal necessity. For they said that the cognition of the intellect is caused by the fact that the images of bodies are imprinted upon our minds: as Boethius relates, V De Consolatione. Against which opinion it is argued from Boethius himself: because the intellect composes and divides, and compares the highest to the lowest, and knows universals and simple forms, which are not found in bodies, and to which the exterior sense does not extend.

Thirdly, Plato and Aristotle are introduced against the aforesaid opinions, who, positing that the intellect differs from sense, attributed the cause of our knowledge not to bodies, but to immaterial things: the former to the Ideas, the latter to the agent intellect.

The authority of Scripture is also introduced, Job 35, and the Psalm, where it is said: Who teacheth man knowledge.

VIII. The second conclusion is⁷: Although the heavenly bodies cannot directly be the cause of our intelligence, yet they operate something toward this indirectly, namely by acting upon something from which the action of the intellect is either helped or hindered.

It is proved. Because in us the operation of the intellect cannot be completed without the operation of the corporeal powers, which are the imagination, and the memorative and cogitative power. The sign of this is twofold. One is that, when the operations of these powers are impeded on account of some indisposition of the body, the operation of the intellect is impeded: as happens in frenetics, that is, those seized in mind, and lethargics, that is, the forgetful. Another is that the goodness of the disposition of the human body makes one apt for understanding well, from the fact that the aforesaid powers exist stronger: as is clear from II De Anima. But the disposition of the human body is subject to the heavenly bodies: as is clear from Augustine, V City of God, chap. VI; and from Damascene, the second book.

From which St. Thomas infers first that, just as a physician can judge of the goodness of the intellect from the disposition of the body as from a proximate disposition, so an astrologer can from the celestial motions as from a remote cause.

Secondly, he infers that the saying of Ptolemy in the Centiloquium concerning the goodness of intelligence can be verified according to this mode, when he says that, when Mercury in the nativity of someone is in any of the houses of Saturn, and he himself is strong in his being, he gives goodness of intelligence deep down in things.

IX. But against this second conclusion and its corollaries it can be argued by the reasons of Giovanni Pico, a most ingenious man, in the book Against the Astrologers ⁸, who holds that the heavenly bodies are universal causes of these inferior things, and that the diversity of effects occurring in these inferior things is to be referred only to proximate causes, and not to any constellations, or positions of the stars. From which it follows that the cause of the diversity of intellects arising from the diverse disposition of the body is some particular power, and not the diverse position of the stars. Whence it comes about that it is also false that an astrologer can judge of the goodness of the intellect from celestial motions, as is said here; and that the saying of Ptolemy, which St. Thomas strives to verify, cannot be saved.

For he argues first thus. The heaven is a universal cause. A universal cause does not distinguish effects, but only proximate causes do, both specific and singular. Therefore the heaven is not the cause of the diversity of effects in these inferior things.

It is confirmed first ⁹. There is no position of the stars under which a lion is not born from a lion, a horse from a horse. Therefore the diversity of things is to be ascribed not to the position of the stars, but to the diversity of particular causes.

It is confirmed secondly ¹⁰. Those born at the same moment from diverse parents, within the same latitude and longitude of the same region, we see to be most diverse in fortune, genius, and body. Therefore their diversity arises from particular causes, which are diverse, not from the position of the stars, which is one.

Secondly it is principally argued thus ¹¹. The heaven acts upon these inferior things by light and motion only, by which nothing else is communicated to matter than motion, light, and heat. But these flow from all the stars. Therefore there are not diverse influxes of the heavens according to the various position of the stars.

X. For the evidence of this difficulty, it must be considered first, from the doctrine of St. Thomas I Sent., d. xxxviii, a. 5, and in many other places, that, since the first and universal cause effects particular effects by mediating secondary causes, its power must be received in the secondary cause, so that it may be brought, as it were, through it to the effect. But because whatever is received in another is received according to the mode of the recipient, the power of the universal cause receives a certain limitation, and determination to determinate effects, from the secondary cause in which it is received. For that reason it was said above ¹² that many effects happen contingently, although the first cause is necessary, on account of the contingency of the secondary cause, in which the power of the first cause receives limitation. And by the same reason, while some universal cause acts toward the generation of a horse, by mediating a horse it generates a horse; and while it acts toward the generation of an ox, by mediating an ox it generates an ox. By like reason, while it acts by mediating a horse of weak power, it generates a weak and feeble horse; and while it acts by mediating a strong horse, it produces a strong and robust horse; and so of others.

Pico therefore, an otherwise most learned man, seems to be deceived, because, since he saw that the heaven is a universal cause, he thought that the diversity of things cannot be referred to its power: although nevertheless the opposite, on account of this reason, is to be held. For if the heaven is a universal cause, without which no corporeal thing either acts or can act, it is necessary for us to confess that the heaven is the cause of all diversity, as being that which moves all secondary causes to act, from which diverse effects arise. For that reason we posit that the diversity of genius arises from the impression of the heaven, indirectly however and transversely and by a certain occasion: since the heaven, as a universal cause, effects diverse corporeal dispositions according to which the sensitive powers are varied, which the intellect uses in its work.

But we do not refer the variety of these corporeal dispositions to the heaven in such a way as if it arose from it alone, with no mediating cause intervening: but because the heaven uses a secondary cause, which is made more vigorous while acting when the heaven exists in such a disposition, than if it were not such disposed. The heaven itself also, by mediating some particular cause, removes the impediments by which the fitting disposition of matter, or also the action of the secondary agent cause, could be impeded. For it is not unfitting that some effect should arise from secondary causes as they are the instruments of another agent, which would not happen solely from the power of their own nature: just as we see that by the operation of art wonderful effects are made by mediating fire, and other natural causes, which would not arise solely from those natural causes.

XI. It must be considered secondly, from the doctrine of St. Thomas, II Sent., d. 15, a. 1 and 2; Prima, q. 70, a. 1, ad 2; ¹³ in Qu. de Spirit., a. 8, ad 12; and II Caeli, lect. 10, that although all the stars act by motion and light as by a power common to all, nevertheless, besides the common power of light, individual stars have their own proper powers by which they are the producers of diverse effects, which powers follow upon the species of each star. And because according as a star is diversely related by its motion to another star and to lower things, it produces diverse effects, therefore according to diverse aspects and conjunctions stars imprint diversely and operate diversely, according as a lower star participates in the power of a higher star; and according as from several acting powers something is effected that could not be done by a single power alone; or even according as one star, from its determinate power, is naturally apt either to help or to hinder another star from its proper effect; just as we see in lower things one cause helping another, but another hindering, for a cause is helped toward its effect by the application of heat, which is hindered by the application of cold. So also we say, following the opinion of Ptolemy cited here, that if Mercury, at someone's birth, should be in one of the houses of Saturn, and itself strong in its being, Mercury is helped by that position toward causing—yet through the mediation of secondary causes which it uses as instruments—that disposition of the body which is most suitable for the sensitive powers, from which disposition of the sensitive powers it is brought about that someone can most effectively use the operation of the intellect, whence someone is said to be of the best talent. And therefore St. Thomas says very well that the astrologer can judge of goodness of talent from the motions or from the position of the stars as from a remote cause, concerning which goodness the physician will judge from the habit of the body as from a proximate cause.

Hence what our Pico says, that if the stars have any power besides light and motion, it is universal to all lower things, is completely false. For certain powers are given to stars for determinate effects, not for all effects: although by the common nature of light they can accomplish something in all these lower things. And yet those powers can be called universal, insofar as they are not determined to only one individual, but are extended to many individuals and to manifold differences of their effect, and cooperate with many particular causes disposed in various ways.

Moreover, because my purpose is not to attack the opinions of others, but only to interpret the statements of St. Thomas in this Book, and to defend them from all calumny, I will not linger over the refutation of this opinion, but will respond only to the objections.

XII. To the first, ¹⁴ therefore, speaking absolutely, the minor premise is denied. For I say that a universal cause distinguishes effects through the mediation of secondary causes: which is proper to a corporeal universal cause, although through itself a cause of this kind does not distinguish such effects.

If, however, it is understood that a universal cause does not have in itself diverse powers by which it may produce diverse effects, but that this is proper to secondary causes:—it is said first, that it is not unfitting for a corporeal universal cause according to diverse parts to have a diverse power for producing diverse effects, through the mediation of particular causes: just as diverse arts use diverse instruments for diverse effects. Now the heaven, understanding by the name of heaven the totality of the spheres and stars, we say has diverse powers according to the diversity of the spheres and stars; and is a universal cause not only insofar as by motion and light it operates upon all things, but also insofar as by diverse powers of this kind it acts upon all lower things, namely by producing one effect through one power, and another through another.

It is said secondly, that any star also can be called a universal cause, although it has a certain power distinct from the power of another star, and produces an effect distinct from the effect of another. Both because by motion and light, which are common to all celestial bodies, it acts upon these lower things; and because by its proper power, following upon its species and nature, it can produce diverse effects, insofar as the powers of many particular causes are unitedly contained within it, just as Pico also thinks that all lower effects are unitedly contained in light.

2. To the first confirmation, the consequence is denied. For that only a lion is generated from a lion is also by the power of the stars: because the heaven does not actuate particular effects except through the mediation of a secondary cause, and for producing diverse and determinate effects it uses diverse and determinate secondary causes, just as a craftsman uses diverse instruments for diverse effects. Hence, just as this is invalid: The blacksmith's art produces only such an effect through such an instrument, and only such through such an instrument. Therefore the diversity of these effects does not depend on the craftsman, but only on the instruments; so this is invalid: No matter how the stars are disposed, only such effects proceed from such particular causes. Therefore secondary causes alone are the causes of diverse effects, and not the position of the stars.

It is said secondly that, although only a horse is born from a horse, nevertheless there is a certain disposition of the stars under which a horse is able to generate a horse, and if it did not exist, it would not generate (which disposition nevertheless does not consist in an indivisible point, but has a latitude), and so of others. Hence we see that certain animals are fit for generation at certain times of the year which at other times of the year do not generate.

3. To the second confirmation, the consequence is denied. For that there are diverse fortunes or dispositions of those born at the same moment, and in the same longitude and latitude, does not prove that the position of the stars does not act upon these lower things: but it proves that it does not act necessarily, and that the influx of the heaven receives a limitation in the secondary cause. For because celestial bodies do not act except in matter, and not except through the mediation of particular agents, the influx of celestial bodies can be hindered both from the indisposition of the matter and from the indisposition of the particular agent, in which the power of the heaven receives limitation. Hence it stands together that the position of the stars is naturally apt to produce this effect; and yet in one case it is not produced, on account of some hindering factor, whether it be a lower cause or even another constellation; while in another, in which hindrances do not occur, it is produced. For this reason it is granted indeed that the diversity of these effects is referred to secondary causes as to proximate causes: yet it is denied that diverse effects ought not to be referred to diverse positions of the stars as to remote causes.

Moreover, it could be argued conversely thus: Sons who are generated from the same parents, and are instructed by the same master and teacher, and educated with the same foods, are found to be of diverse morals, and to be driven by diverse and varied fortune. Therefore their diversity proceeds in some part not from particular agents, but from a diverse position of the stars.

4. To the second principal argument, ¹⁵ it is said first, that the antecedent is false. For as has been shown, according to the mind of St. Thomas, the stars, besides motion and light, have proper powers following their species, by which they produce determinate effects in these lower things.

It is said secondly that, even granting the antecedent, the consequence does not hold. Because, as is said in On Spiritual Creatures, in the article cited above, light is not of the same nature in all stars. Therefore, besides the common effects following upon the common nature of light, each star by its light can produce some particular effect.

XIII. But against the aforesaid responses, insofar as they posit that besides light there are particular powers in the stars; especially against the statement of St. Thomas in II Caeli, ¹⁶ that all celestial bodies, according to the common power of light, have the property of heating; but according to proper powers, they also have the property of cooling, Pico argues thus: ¹⁷ The light that is posited in celestial bodies either contains eminently all four primary qualities, or not. If the first, it is argued thus: Something less perfect than what belongs to it from its common nature cannot belong to anything from its proper nature, since a more contracted difference always adds a degree of perfection to a universal difference. But that quality which contains every quality is more perfect than that which is only productive of coldness. Therefore, etc. — If the second, then thus: Nothing is suitable to anything from its proper nature that is repugnant to the properties belonging to it from its common nature. But to heat belongs to stars from the common power of light. Therefore to produce cold cannot belong to any of them from a proper and peculiar power.

XIV. For the evidence of that statement of St. Thomas, and also of those things that have been said, it must be considered that we can understand in two ways that the heaven, or a star, cools and produces other effects through its proper power, but produces heat through the common nature of light. In one way, that that proper power is a quality really distinct from light. — In another way, that it is the light itself determined to the species of this star: so that this light, insofar as it is light absolutely, or according to the common nature of light, has the property of heating; but insofar as it is such a light, namely following the species and nature of this determinate star, say Saturn, it has the property of cooling, and of producing other determinate effects.

Now although each sense can be saved according to the mind of St. Thomas, yet in the places cited above ¹⁸ he seems to incline toward the second sense. For he attributes the diversity of effects proceeding from the stars to the rays of diverse stars. ¹⁹ — And expressly in II Sent., where cited above, ²⁰ he says that, besides the nature of light which is common to all celestial bodies, each star has a determinate power following upon its species, by reason of which its light and motion have the property either of cooling or of moistening. — Similarly in d. 13, a. 3, he says that every alteration that is in lower things is perfected through the power of light, because the heaven is the primary alterant.

Now I understand this concerning a star to which light is connatural: for according to that light, insofar as it is such light, it operates all its effects that are proper to itself. But if light comes to it from without, and with a certain variation, as we see in the moon, perhaps it is then necessary that its natural power by which it cools and moistens be distinct from the received light, by which it heats in some way.

2. But whichever sense is held, the objection does not proceed: although it seems rather to be brought against the first sense. Hence, when it is asked, whether light contains eminently all four primary qualities: — holding the first sense, it is said that it does not, but contains only heat, and the quality that accompanies heat. But when it is argued to the contrary, because nothing belongs to anything from its proper nature that is repugnant to what belongs to it from its common nature: — although this properly holds truth concerning an essential common nature, yet it is said that this is true of that which is intrinsically repugnant to the common nature or to its natural property; but it is false of that which is repugnant to it extrinsically, namely by reason of the effect alone. Now it is said that, because the heaven is remote from all contrariety, the heating power in it and the cooling power are not contraries, nor are they intrinsically opposed, just as the species of contraries in the intellect are not contraries: but they are opposed extrinsically only, insofar as one is productive of heat, and the other is productive of cold, which are opposed qualities. Therefore it is not unfitting that they be simultaneously in a celestial body: for in a universal cause it is not unfitting for powers that in particular causes are dispersed and contrary to be united and to exist without contrariety; just as all the powers of creatures are in the highest degree united in God. And the reason for this is that in a universal cause the effect does not have to be according to the same ratio, but it suffices that it be in it in a more eminent way and virtually only: just as heat produced by the sun is not in the sun according to its specific ratio, but only virtually, insofar as in light there is a power productive of heat. — Hence, if it were insisted that contrary effects require contrary causes: it is evident that this has truth concerning particular and univocal causes only, but not concerning equivocal causes, of which kind is the heaven.

Holding, however, the second sense, it is said that in the light of any star having the property of cooling and producing other qualities, all those qualities are eminently contained, not insofar as it is light absolutely, because as such it has the property only of heating: but insofar as it is such light, following this star. But when it is argued to the contrary, because something less perfect than what belongs to it from its common nature cannot belong to anything from its proper ratio: — it is evident that it is not argued against the aforesaid sense. Because we do not say that, beyond the light containing all those qualities, there is another power in the star productive only of coldness: but that its light, which, insofar as it is light, is only productive of heat, insofar as it is light following this star, has the power to be also productive of other qualities and other effects; which is more perfect than merely heating.

It is said, moreover, that that quality which is productive of cold, according as it is in the heaven, is not less perfect than that which is productive of all four qualities, since they are one and the same power in reality: just as the divine power productive of man is not in God less perfect than the power productive of all things.

XV. But another doubt arises. For it seems to follow, if in one star there is a heating power and a power productive of coldness, whether they are one or diverse powers, that it will simultaneously cause heat and cold in the same thing, for instance that the moon will simultaneously heat and cool the air: since a star is a natural agent. But this is impossible.

2. It is said first that, since the heaven is a universal and corporeal cause, it does not act upon these lower things except through the mediation of secondary causes. Therefore it does not follow that it induces contrary qualities in one and the same subject: but in diverse subjects, according as particular causes operate upon diverse subjects; for through the mediation of fire, it heats some things; but through the mediation of water, it cools and moistens others.

It is said secondly, that the diversity of matter also contributes to the diversity of effects. For just as the heaven by the same light hardens clay and melts wax on account of the diverse disposition of the matter, so the diverse disposition of the matter brings it about that something receives heat from the heaven, but not coldness; while on the contrary another receives cold, but not heat.

It is said thirdly, that perhaps, according to the opinion of those holding that contrary forms in remiss degrees can be simultaneously in the same subject, it is not unfitting that cold and heat in degrees in which they are compatible be simultaneously caused by the heaven in one and the same subject, if we posit that the heaven alters something to heat or cold immediately—that is, not through the mediation of a particular hot or cold agent—by its diverse powers, say the air. For just as it is not unfitting, if a hot and a cold thing are brought near to wood, and the hot thing is stronger, that the wood receive heat from the one, but from the other a certain degree of coldness not repugnant to the degree of that heat: so it is not unfitting for a star, say the moon, simultaneously to cause coldness in the air by reason of its proper power, but to cause some degree of heat in it by the power of light. Hence, although it belongs more to the moon to cool by the power of its proper quality than to heat, nevertheless from the common nature of light it also causes in the air cooled by it some degree of heat not repugnant to its coldness. On account of which nights of the full moon are said by Aristotle, in the book On the Parts of Animals, ²¹ to be warmer: because, namely, the more light the moon has, the more it heats the air according to some degree; although by its proper power it always introduces a coldness more intense than the heat.

It can also be said that it does not follow that contrary qualities are simultaneously caused in the same thing by one star, but only that one power hinders the other from producing its effect in another. For just as heated water is hindered by the incoming heat from cooling, and therefore only heats; so the moon, which according to the property of its nature is cooling, upon the arrival of the fullness of light is hindered from cooling the air, or from producing so much coldness. Nor is it unfitting to posit this in the moon: because the reception of light is not against nature for it, but natural. Therefore, just as it is natural for it to cool when light is removed, so it is natural for it to heat, or to cool less, upon the arrival of light.

These things I would say as far as occurs to me for now. If anything better should occur to the mind, with God's help, I will bring it forward.