Commentaria in Summam contra Gentiles, Liber I

After St. Thomas had made known his purpose in this work, he consequently showed what the manner of manifesting divine truth is ¹. Concerning this he does two things: first he enumerates the things that are to be manifested; second, he determines their manifestation itself, in the following chapter.

As to the first, assuming, according to the opinion of Aristotle and Boethius, that a trained man ought to seek concerning each thing only as much of faith as the nature of the thing admits, he sets down this conclusion: Of those things we confess concerning God, some are such that they can be known by the natural light of reason, while others exceed every capacity of human reason. He leaves the first part as evident: because the philosophers, who used natural reason alone, proved most things about God demonstratively, for instance that God exists and that God is one. — He proves the second part first by three arguments, showing that there are certain intelligibles concerning God which altogether surpass the human intellect; then he confirms it with authorities ².

I. The first argument is this. Whatever can be known in all respects by the natural light of the intellect, its substance also can be comprehended by that intellect. But the substance of God cannot be comprehended by our intellect. Therefore our intellect cannot know by its natural light all things knowable about God.

The major premise is proved. The principle of the whole science of a thing is the understanding of its substance: because, according to the Philosopher, the principle of demonstration is what the thing is. Therefore, according to the mode of cognition of a thing's substance will be the mode of those things that are known about that thing. If, then, the substance of some thing, say a stone or a triangle, is comprehended by the human intellect, no intelligible about it will exceed the capacity of human reason. Supply: — Therefore, conversely, if no intelligible about it exceeds natural light, indeed all things about it can be known naturally, and its substance will be able to be comprehended.

The minor is proved. Only those things that do not fall under sense can be grasped by the human intellect whose knowledge can be gathered from the senses, because our intellect, according to the mode of the present life, receives its knowledge from the senses. But from the senses our intellect cannot be led to see the divine substance, because sensible things are effects that do not equal the divine power. Therefore, etc. — He adds, however, that although sensible things do not lead to knowledge of God's substance, they nevertheless make us know of Him that He is, and other things of this kind which must be attributed to the first principle.

2. For the clarification of the major premise, it must be noted that the intention of St. Thomas is to speak of those knowables that belong per se to a subject: for science extends itself to such things, not to per accidens predicates. For such things, which are also called properties, are contained virtually in the substance of the thing as effects in their cause, where they have a distinction outside the intellect: for they are produced, according to the doctrine of St. Thomas ³, from the substance by a certain natural resultance. But where they are not distinguished, as happens with the passions of being, which are not really distinct from being, the ratio of the subject virtually contains the rationes of the passions, and one is the cause and ratio of the other only in intelligible esse. Since, therefore, the passions are contained in the subject as in their cause, whether with respect to real esse or with respect to intelligible esse, all the passions of any thing cannot be known of it unless its quiddity is known totally, nor can the quiddity of a thing be perfectly known unless all its properties naturally resulting from it are known: just as all the effects of a cause cannot be known in the cause except through a comprehension of the cause, nor can the cause, as such, be comprehended except through an inspection of all the effects into which it can issue.

3. As to the minor premise, it must first be noted that St. Thomas did not say simply that the substance of God cannot be known from sensible things, but added, "so that it may be seen in them what it is": for sensible things, when known, do indeed make us know the substance of God, since all things that are in God are his substance; but they cannot lead us to know him quidditatively as he is in himself, which would be properly to know the substance of God.

It must be noted, second, that an object is said to be adequate to a power in one way, and an effect of a cause in another. For an object is said to be adequate to a power according to a certain community of extension: namely, because whatever falls under the ratio of that object can be attained by such a power, and conversely, whatever can be attained by the power is contained under that object. But since it belongs to the ratio of an effect, insofar as it is such, to depend on its cause, the effect is said to be adequate to the cause, as Saint Thomas seems to intend in the Third Book, chapter 49, when in it the whole power of the cause is expressed. Now I take this to be the case when, by the power of the cause, an effect is produced of as great a perfection as the cause. But when the whole power of the cause is not expressed in the effect, namely because it is not of as great a perfection as its cause—which can indeed be discerned when the cause is able to produce an effect nobler than that one—then that effect is inadequate to the cause. Therefore, since there is no effect of the divine power than which it could not produce a nobler one, and none is of as great a perfection as God, no effect is adequate to it.

It must be noted, third, that because a power follows upon the essence of a thing and is proportioned to it, since the effect equals the power of its cause, the essence also seems to equal the essence: just as man begotten, in respect of his essence, equals the man who begets him. For this reason, from quidditative knowledge of an effect the cause can be known quidditatively. But where the effect does not equal the power of its cause, as happens in divine effects, neither can it equal the essence of the cause. And consequently, from the inspection of the effect itself the cause cannot be perfectly known: but only those things about the cause can be known through such an effect which must be found in the cause in order that such an effect be produced by such a cause; just as, in order that something be produced by another as by a first cause, it is necessary that that cause both be, and be intellectual, and be immaterial. Therefore, from knowledge of the effects of the first cause, though unequal effects, we can know that it is, and that it is intellectual and immaterial, and things similar to these.

II. But concerning this argument a doubt arises, because St. Thomas seems to commit the fallacy of figure of speech in the proof of the major. For he proves it thus: According to the mode in which the substance of a thing is known, such is the mode of those things that are known. Therefore, for that whose substance the intellect comprehends, all things intelligible about it can be known. Here, however, there is a transition from mode to the multitude of intellects, and thus from quality to quantity, where the fallacy of figure of speech is manifestly committed.

It is answered that, just as one essence is the one cause of all its passions, so all its passions agree in one account—namely in this, that they are its natural properties; and the mode of knowing a natural passion is proportioned to the mode of knowing the substance. For of that whose essence is known totally, it is necessary that its natural passion also be known totally. But from the fact that a natural passion is to be known and comprehended totally, it follows that there is no natural passion which is not known. Therefore no fallacy is committed: for the passage is not made immediately from mode to quantity; but from the mode of the essence to the mode of the predicate, which mode of things known numerical quantity accompanies. And Saint Thomas, studious of brevity, touched upon quantity explicitly, so as to give us to understand both the mode which immediately follows from the antecedent and the quantity accompanying it. The explicit argumentation will therefore be this: — According to the mode of knowledge of the substance of a thing is the mode of knowledge of the natural passion known of that thing. Therefore, of that whose essence is comprehended and known totally, its natural passion is comprehended and known totally: either actually, namely, or virtually. But then the natural passion of a thing is known totally when there is none which is not known of it. Therefore etc.

III. The second argument is taken from the degrees of intellectual beings. And it is argued thus: the higher and more elevated an intellect is, the more things it can understand which an inferior intellect cannot grasp. But the divine intellect exceeds the human most of all. Therefore God can know in Himself some things which the human intellect cannot grasp at all.

The major proposition can be seen in men. For the intellect of the rustic and the unlearned cannot at all grasp the subtle reasonings of philosophy, which the philosopher and a man of great genius grasps.

The second point is also evident. For the angelic intellect exceeds the human intellect more than the intellect of the best philosopher exceeds that of the most unlearned idiot: since the distance of one man's intellect from another's is contained within the limits of the human species, whereas the angelic intellect is superior in species. This can easily be perceived, because it knows God from a nobler and more abstract effect: for by the very substance of the angel, which is nobler both than sensible things and than the human soul itself, through which the human intellect ascends to God, the angel knows God by natural cognition, as will be shown below ⁴. But the divine intellect exceeds the angelic more than the angelic exceeds the human. This is made manifest because the divine intellect equals the divine substance and therefore perfectly understands itself; but the angelic intellect does not know what God is, since its own substance, by which it knows God, is an effect whose power does not equal its cause; and therefore the angel cannot know by natural cognition all that God knows of Himself. Therefore the divine intellect exceeds the human to the highest degree.

2. For the declaration of the major, with its proof, it must first be known, as Saint Thomas says, that something can come to be unable to be known by a power in two ways: either, I say, because it does not fall under the object of the power, as sound cannot be taken in by sight; or because, although it is contained under the object, it is nevertheless disproportionate to the power, as something very bright cannot be seen by the eye of a bat. Therefore, that certain philosophical subtleties are grasped by the intellect of one man but cannot be taken in by the intellect of another is not for this reason, that they are comprehended under the common object of the one intellect but not under the object of the other intellect; but because they are proportionate to the one intellect and disproportionate to the other intellect, since the one intellect can penetrate the natural quiddities, while the other, by its dullness, cannot.

It must be known, secondly, from the doctrine of St. Thomas (Iª, q. 85, a. 7, and II Sent., d. 32, q. 2, a. 3) that just as all human bodies are of one species, and yet this specific unity admits a breadth of diverse individual degrees—since one man is well-complexioned and adorned with beautiful form and comely appearance, while another is deformed and ugly and badly complexioned—so too, together with the specific unity of souls there stands a diversity of their individual degrees, so that as one body is substantially more perfect than another individually and of nobler complexion, so one soul is individually nobler than another, and by this one man is endowed with a more excellent intellect than another. For individual forms are created commensurate with bodies substantially, such that by its commensuration to this body this soul is distinguished from that one individually. Hence as one body is more nobly complexioned than another, so one soul must be nobler than another. — Yet for all that, one man is not on this account more a man than another, though he is a more perfect man: because we use the word "more" only in forms in which change occurs between more and less; which does not occur in the intellectual soul, since each one preserves immutably that substantial perfection it received from the beginning. One man, therefore, can be of better power in understanding than another because he has a better and nobler soul; although this can also arise from a better disposition of the sensitive powers, inasmuch as the intellect depends upon them for its operation.

IV. The third argument proceeds from the greater. It seems that we know all that is knowable about sensible things rather than all that can be known about God, since the former are closer to us and more proportionate to us. Yet we are ignorant of many properties of sensible things, or we cannot discover their complete explanation. Therefore, much less can we naturally know all that is knowable about God.

V. It is confirmed by the authority of the Philosopher, II Metaphysics, and by many authorities of Sacred Scripture⁵ For Aristotle says that our intellect is related to the most manifest things in nature as the eye of a bat is to the sun. And in Job 11 it is said, "Perhaps you may find traces," etc.; and in chapter 36, "Behold, God is great," etc.; likewise in I Corinthians 13 it is said, "We know in part," etc.

On the authority of the Philosopher, it must be noted that this does not imply total ignorance of divine things, but rather a certain obscure knowledge and difficulty of cognition. For just as the bat cannot fix its keen sight upon the very splendor of the sun, so neither can our intellect naturally understand the divine essence as it is in itself, comprehending its quiddity.

Hence the error of the Manichaeans is refuted, and that of many unbelievers who at once supposed that those things which are revealed by God through the ministry of angels, and which cannot be investigated by human reason, must be rejected as false. The same thing happened to them as to an unlearned man who would say that what philosophers say is false because he could not grasp it.

VI. Concerning this part of the conclusion which Saint Thomas proved⁶, Scotus agrees in part, and in part dissents. For he holds with Saint Thomas that there are many truths about God knowable which no one can discover naturally, since their cognition cannot be caused by the agent intellect and the phantasms. But in this he dissents, because he holds that this cognition is indeed supernatural when the possible intellect is compared to the agent; yet, when it is compared to the actual knowledge in itself, it is natural to it, since the possible intellect is naturally perfected by any cognition whatsoever, and is naturally inclined toward any cognition whatsoever. Saint Thomas holds the opposite of this, taking natural potency properly, and not as extending itself also to the obediential, in III Sent., d. XXVI, q. 1, a. 2, and De Veritate, q. XVIII, a. 2, where, on the mind of the Commentator, IX Metaphysics, he holds that a natural passive potency does not extend itself except to those things to which its natural active potency extends itself. From this, in the question in De Veritate, he concludes that the possible intellect is not naturally in potency except to those forms which are made intelligible by the agent intellect.

The position of Saint Thomas is confirmed by the course and reasoning of Aristotle in Book III of De Anima, where he proves the necessity of the agent intellect, text 17⁷. For by this argument he proves that there must be posited in the soul an agent intellect, because in a nature in which there is a passive potency, an active potency must be posited. Now it is clear that Aristotle is speaking of a proximate and proportionate active potency; otherwise his argument would not prove his thesis. Therefore, if some passive potency is naturally inclined toward some act, it must be that it can receive that act from some natural and proportionate agent.

But if it is pressed further, as Scotus presses it, IV Sent., d. XLIX, q. XI, ad 2, that in the body there is a receptive potency for the intellectual soul, and yet it cannot be produced by any natural agent — it is answered, according to the mind of St. Thomas, Pot. q. III, a. 9, ad 5 and 6, that it is not necessary for every natural agent to produce the essence of the form; it suffices that it be a dispositive cause of the matter, and be the cause of the union of the form with the matter. For if the form is not subsistent, the natural cause is the cause of the form itself; but if the form is subsistent, as is the rational soul, the natural cause is the cause of the disposition of the matter and of the union of the form to the matter, but not the cause of the form. Hence this consequence is denied: No created agent, whether natural or otherwise, can produce the intellectual soul; therefore, matter cannot be reduced to act with respect to the intellectual soul by any natural agent — for it is said that the opposite of the consequent can stand together with the antecedent: for a natural agent can reduce matter to the act of the form by causing the dispositions toward the form and the union of the form to the matter, and yet not cause the form itself.