Commentaria in Summam contra Gentiles, Liber I

After St. Thomas had determined the mode of knowing divine truth absolutely, he now determines it comparatively with respect to human reason ¹. In regard to this he does two things: first, he compares the truth that is believed to the truth known naturally; second, in the following chapter, he compares the first truth to natural reason itself.

I. First, therefore, he compares truth to truth. And he sets down this conclusion: The truth of faith is not contrary to the truth naturally implanted in us. Regarding which it must be noted that the first indemonstrable principles, known to us naturally, virtually contain the knowledge of all other things that can be known by natural investigation; and things are true insofar as they accord with the aforesaid principles. Therefore, from the fact that it is shown that the truth of faith is not contrary to the knowledge of the first principles, it is also evident that it is contrary to no other truth naturally known. Now this conclusion is proved in several ways.

First. That which is contrary to the true must be false: since the true is not contrary to the true, but only to the false, as appears from their definitions. But the first principles cannot be false, nor can they even be thought to be false. Likewise, that which is held by faith, so evidently confirmed by God, it is not lawful to believe to be false. Therefore etc.

For the clarification of the greater point, it must be noted that, just as the account of the true consists in the adequation of intellect and thing ², so the account of the false consists in inadequation: for which reason it is said in Metaphysics IV ³ that the false arises from this, that something is said or appears to be which is not, or not to be which is. True knowledge, therefore, will be that by which it is known that a thing is as it is; but false knowledge, that by which it is known that a thing is as it is not. And because to apprehend being and non-being are contraries, as is said in Peri Hermeneias II ⁴, therefore true knowledge and false knowledge are contraries. It is well said, then, that the false is contrary to the true, whereas the true is not, as is evident from their accounts: because an adequate cognition of a thing is not contrary to an adequate cognition of the thing; but rather an inadequate cognition of a thing—by which, namely, it is judged that what is, is not, wherein the account of the false consists—is contrary to the adequate cognition of the thing, by which it is judged that the thing is as it is, wherein the account of the true consists.

It must also be noted, for the clarification of the minor premise, that Saint Thomas speaks in different ways about first principles and about the things that are of faith, in order to show that we have knowledge of these in different manners. For principles must be most true and appear most true, in such a way that they cannot even be thought to be false: as the Philosopher says of this first principle, It is impossible for the same thing to belong and not to belong to the same thing at the same time, IV Metaph.⁵ For although someone might say in words that this is false, he cannot nevertheless think it in his mind: because then contraries would belong to the same thing at once, as the Philosopher argues. But those things which are of faith, although they are in themselves most true, do not yet have their truth apparent to us from the proper notions of their terms; rather, they are judged to be true only in a general way because they have been divinely revealed, as has been confirmed by miracles, as we said in the preceding chapter ⁶ Therefore, to intimate this different manner in which we stand with respect to knowing these things, Saint Thomas said of principles that it is evident that they are most true: but of what is held by faith he said that it is not lawful to believe it to be false.

2. From this reasoning of St. Thomas, the reasoning of Robert Holcot is excluded, in Book I of the Sentences⁷, where he argues that the things which are of faith are against natural reason, because natural reason dictates that the opposite is true. For it is clear from what has been said that this assumption is false.

It is also clear from what has been said that what he assumes in another respect is false, namely, that the articles of faith are contrary to reason not only for rustics but also for the wise: for instance, that a woman should conceive without the seed of a man. For it is said that they are not contrary to the reason of those truly wise. For if such men say that it is impossible for a virgin to conceive, they say this considering the order of secondary causes, but not considering the order of the divine power. And if anyone said this to be impossible for God, they were not truly wise nor truly philosophers. Hence Saint Thomas, on Boethius' De Trinitate, q. II, a. 3 ⁸, says that if anything is found in the sayings of the philosophers contrary to the faith, this is not philosophy, but rather an abuse of philosophy arising from a defect of reason.

II. Second. What is contrary to divine wisdom cannot be from God. But what is contrary to first principles is contrary to divine wisdom. Therefore it cannot be from God. Therefore those things that are held by divine revelation cannot be contrary to natural knowledge.

The minor is proved. What the teacher induces in the soul of the student contains the knowledge of the doctor, unless he teaches fictitiously. But the knowledge of principles naturally known has been implanted in us by God, since God is the author of our nature. Therefore divine wisdom contains these principles. Therefore what is contrary to them is contrary to divine wisdom.

Concerning this argument, it must be noted that the containment by which it is here said that the teacher's science contains the disciple's science is not the virtual containment of an active principle: since, as Saint Thomas says, Iª, q. CXVII ⁹, science is not an active quality, but stands only in the manner of a directive principle in operating. Now the teacher's science is said to contain the disciple's science insofar as it extends to the same knowables and to the same truths to which the disciple's science extends: for it is the same truth that the disciple knows and the master, because the master moves the disciple to know the same things that he himself knows. Hence that containment could be called perfectional and similitudinary: in the way in which a square contains a triangle, and one white thing another white thing.

2. But a doubt arises concerning the last inference. For it does not seem to follow: Divine wisdom contains the principles, Therefore what is contrary to the principles of divine wisdom is contrary to it. For this does not hold: Divine power contains whiteness because it can produce whiteness, Therefore what is contrary to whiteness is contrary to divine power. It will be said that, just as divine power can be the cause of contraries, inasmuch as it contains each of them virtually, so divine wisdom will be able to be the cause of opposed cognitions, as containing both virtually and supereminently. Nor must it follow that, if one cognition be contrary to another, it is therefore also contrary to divine wisdom.

To make this difficulty evident, it must be considered that the containment of which we are speaking here is not, as we have already said, the containment of an active principle, but that of a certain likeness and agreement, insofar as two cognitions agree in the same truth known. And because one cognition is not contrary to another except because they terminate in opposite enunciables—just as the cognition by which a man is judged to be risible is contrary to that by which he is judged not to be risible—therefore, if one cognition is contrary to another, it will also be contrary to that which is like it, since it agrees with it in the object known. For that which is contrary to this human cognition, Man is risible, is contrary to every other cognition, whether angelic or human, by which man is known to be risible. This consequence therefore holds well: Divine wisdom contains the knowledge of first principles; therefore the cognition contrary to the knowledge of those principles is also contrary to divine wisdom; because by this containment nothing else is understood than agreement in that truth known through divine wisdom and the knowledge of first principles.

To the objection, however, it is said that it is not similar: because there the argument concerns only the virtual containment of the active principle, according to which the same thing can contain contraries eminently; but here we speak of a containment proper also to science, which is perfectional and involves a certain likeness, unity, and fittingness in the same object, according to which one knowledge cannot contain opposite knowledges; although divine wisdom is indeed the cause of our natural cognition. — But when it is said that the science of opposites is the same ¹⁰, this is understood, as regards incomplex terms, to mean that the consideration of both opposites pertains to the same science, just as the science of the healthy and the sick is the same; but as regards complex propositions, to mean that by the same science it is known that one part of a contradiction is true and the other false.

III. Third. If such a contrariety existed, our intellect would be impeded from the knowledge of truth. But this cannot be from God. Therefore, etc. — The consequence is proved. By contrary reasons the intellect is impeded from the cognition of truth. Therefore, if contrary cognitions were sent to us by God, our intellect would be impeded from the cognition of truth.

For the proof of the consequence, it must be considered that the contrariety of argumentations is taken from the opposition of the conclusions to which they terminate: because an argumentation is a certain movement of reason, and movements of contraries terminate in contrary terms. It is therefore the same thing for reasons to be contrary as for them to cause contrary cognitions. And it is the same thing for the intellect to be impeded and confounded by contrary reasons as for it to be impeded by contrary cognitions caused by one or the other of them. Now divine wisdom is proportioned to demonstration with respect to this, that it causes cognition in us. On account of this, just as contrary reasons impede the intellect because they cause contrary cognitions, so, if divine wisdom were to cause contrary cognitions in us, it would impede the intellect from the cognition of truth. This cannot be from God by acting (except perhaps on account of a mystery or a utility), but well by not acting, that is, by not infusing the light by which something may be understood: just as neither is sin of fault from God except by not infusing grace.

IV. Fourth. Either these cognitions will be together in the intellect, or, when one arrives, the other departs. Not the first: because contraries cannot be in the same thing at once. Nor the second: because natural cognition always remains; for things that are natural, while the nature remains, cannot be changed. Therefore they are not contraries. — It is confirmed by the authority of the Apostle and of Augustine.

2. But a doubt arises. For it is natural for water to be cold, and yet coldness is removed from it while the water remains, namely when it is heated. Therefore it is false that things which are natural cannot be changed while their nature remains.

It is confirmed. For St. Thomas himself, in II-II, q. 57, a. 2, ad 1, says that natural things are always present in immobile things, but not in mobile things, of which kind is human nature. Therefore, although some knowledge is natural to man, it can nevertheless be separated from man while he remains.

3. In answer to these doubts at once, it is said first that "natural," as St. Thomas holds (Book IV, d. 26, q. 1, a. 1), is said in two ways: namely, either of what is caused by the principles of nature with necessity, or of what nature inclines toward. This proposition, therefore—that natural things cannot be changed while their nature remains—is to be understood of natural things in the first way; and it is true both in mobile and in immobile things. But of the natural in the second way it is true only in immobile things, not however in mobile ones: because according to a change of nature even such natural things can be changed and impeded, while the substance remains in its essential perfection. Hence St. Thomas does not contradict himself: for here he speaks of the natural in the first way, but in the cited passage of the natural in the second way.

It is said secondly that it is natural for water to have coldness, yet within a certain latitude: that is, from the essential principles of water there follows some degree of coldness within that latitude, nor can water fail to have some degree of that coldness; indeed, if the coldness were remitted to a degree below that whole latitude, say below the latitude which is from two to six, the nature of water would cease. Therefore, although water, left to itself and unimpeded, is led by nature, so inclining, to the highest degree of that latitude of coldness, it can nevertheless be prevented by violence from the contrary, so as not to have that highest degree of coldness; yet by no heating whatsoever can every degree of coldness be removed from it entirely, its nature remaining. Hence we may say that some degree of coldness is natural to water as caused absolutely by the principles of its nature, and this cannot be removed from water; but other degrees of coldness are natural to water as those to which the nature of water, impediments being removed, leads it; and these can be removed from water by violence and for a time.