Commentaria in Summam contra Gentiles, Liber II

There were also some who, although they did not say that the intellectual soul is a body, nevertheless said that the intellect is a bodily power, holding that the intellect does not differ from sense: except perhaps accidentally, as is said in Book IV, d. XLIV, q. 1, a. 1, qu.^a 1, inasmuch as they said that man has intellect above the other animals because in him, on account of his excellent complexion, the sensitive power is more vigorous.

I. Against these, Saint Thomas also argues¹. And first thus: Sense is present in all animals, but intellect is not. Therefore sense is not intellect. — The antecedent is proved as to the second part: because other animals besides man do not perform diverse and opposed operations, but the same and uniform operations of the same species, as is evident in the swallow; for every swallow builds its nest in a similar way.

For the declaration of this reasoning, it must be noted, from the Philosopher, Metaphysics IX Metaph., texts 3 and 10², that rational powers differ from irrational ones because rational powers can extend to opposites, namely to act and not to act, when the passive is brought near the active in that disposition in which the passive can suffer and the active act; and they can also extend to opposite and contrary actions, just as a physician by the art of medicine can introduce health and sickness. Irrational powers, however, cannot fail to act when the passive is brought near in a sufficient disposition; nor can they extend to opposite actions except per accidens, but are determined to one: as heat cannot fail to heat when a disposed thing capable of being heated is sufficiently brought near to it; nor can it cool except per accidens, insofar as by opening the pores it makes the hot within exhale, or in some other way. Similarly, a sheep, seeing a wolf coming, cannot fail to flee, nor can it love or pursue and desire him. On account of this difference of powers Saint Thomas argues most fittingly from the effect that brute animals do not have intellect, because they do not perform diverse and opposite operations: that is, they do not have dissimilar and opposite operations with respect to the same object, but all things of the same species have the same and uniform operations.

But it must be noted that when we say that the rational powers can be directed toward opposite actions, or toward opposites, this is not to be understood with respect to all the things to which a power extends: because, as is taught by Saint Thomas, Prima, q. 62, art. 8, ad 2, and IV Sent., d. 49, q. 1, a. 3, quaestiuncula 2, ad 1, this is not true of those things toward which they are naturally ordered and which are determined for them by another. For the will cannot fail to adhere to the good insofar as it is good; nor can the intellect fail to assent to the first principles known naturally. The proposition of the Philosopher therefore holds true with respect to opposites that fall under choice, and with respect to those things that are ordered to an end: as is said in II Sent., d. 7 ³, a. 1, ad 1. — Although one could say, following the words of Saint Thomas which we have cited, that the rational powers, insofar as they are rational, are always related to opposites. But with respect to those things toward which they are determined, and toward which they are naturally inclined, they are not rational powers, but rather irrational and natural ones.

2. But a doubt arises concerning what has been said, namely that brute animals do not perform diverse and opposite actions. For where there is the voluntary, diverse action is possible. But, as the Philosopher says in Ethics III, ⁴, children and other animals share in the voluntary. Therefore etc.

It is answered, according to the doctrine of Saint Thomas at Iª IIae, q. 6, a. 2, that the voluntary can be taken in two ways: namely, according to its perfect notion; and according to its imperfect notion. In the first way, the voluntary is properly said from the will. And it is said to be so when, the end having been apprehended, someone deliberating can be moved toward the end or not moved. And thus it does not belong to brute animals. — In the second way, it is said from some participation in will, on account of some conformity to it. And it is said to be so insofar as one who apprehends the end is moved toward the end, though not by deliberation, but suddenly and necessarily. It is in this second way that Aristotle understands the voluntary to belong to brutes, but not in the first way. — Hence, when it is assumed that where there is the voluntary there can be a diverse operation: it is said that this is true of the voluntary according to its perfect notion, but in that way it does not belong to brutes, as has been said; not however of the voluntary in the second way.

It can also be answered in a second way, as Saint Thomas answers in II Sent., d. xxv, a. 1, ad 6, that Aristotle does not take "voluntary" properly, in which sense the major premise is true, but broadly, namely insofar as the voluntary is distinguished from the violent. For thus everything whose principle is within itself is said to be voluntary. And thus, since brute animals have within themselves the principle of their operations, their operations are called voluntary improperly. But where there is a voluntary of this kind, it does not follow that contrary and dissimilar operations can be there.

II. Second. Sense is not cognitive except of singulars; but the intellect is cognitive of universals. Therefore, etc. — The antecedent is proved as to its second part: because we know this by experience. As to the first part, however: because sense knows through individual species, received as they are in bodily organs.

2. Concerning this proposition, that sense is cognitive only of singulars, there is a doubt. For every power is cognitive of its object. But the object of each sense is universal: for the object of sight is color in the universal, not this color; and so with the other senses. Therefore sense is not cognitive only of singulars.

To make this evident, it must be considered that the universal, as universal, can be considered in two ways: in one way, as it has objective esse in the intellect; in another way, as it has esse fundamentally in things. Now, just as it has esse in two ways, so it can be known in two ways: in one way, through complete abstraction from singulars; in another way, insofar as it has its foundation in singulars. In the first way, it is known only by the intellect, whose role it is to abstract one thing from another. In the second way, it can also be known by sense: namely, when sense is directed to a singular thing only insofar as it grounds a universal nature; for thus we say that sight sees universal color, because it does not see this white thing except insofar as it grounds the character of color, and likewise this black thing and the other colors. Hence the particular is that which is known materially, but the universal is that which is known formally, namely as that under whose character the particular is known.

To the argument, therefore, it is said that sense certainly knows the universal in the manner described, and as the reason for knowing: but this is not against what is said here. For Saint Thomas speaks of that which is known materially, as first terminating the act of knowing. Now such a thing is singular on the part of sense, but universal on the part of the intellect: although the universal is also known formally by sense as the reason for knowing, holding on the side of the object.

III. Third. The senses know only corporeal things: since sensible qualities, which are the proper objects of the senses, and without which the senses know nothing, exist only in corporeal things. But the intellect knows incorporeal things as well: for instance, wisdom, truth, and the relations of things. Therefore, etc.

It must be noted that when Saint Thomas speaks of the knowledge of corporeal things through sense, he does not mean knowledge of corporeal substance with respect to its substance and essence: for, since substance is not known by sense in this way except per accidens, the comparison of sensitive knowledge with respect to corporeal things to intellectual knowledge with respect to incorporeal things, which are known per se, would not be fitting. Rather, by sensitive knowledge of corporeal things he means knowledge of them as they are under their proper sensible qualities, that is, as they are signified by the name "colored" and other such names of accidents. For it is thus that they are known per se by sense.

IV. Fourth ⁵. The sense does not know itself, nor its own operation, but this belongs to a higher power, as is proved in the book On the Soul. But the intellect knows itself and its own operation. Therefore etc. — The first part of the antecedent is proved by the example of sight, which neither sees itself nor sees itself seeing.

2. Concerning this proposition, that Sense does not know its own operation, a doubt is raised. For Saint Thomas seems to say the opposite in Verit., q. 1, a. 9, and q. x, a. 9, where he holds that sense turns back upon its own essence, though by an incomplete return, insofar as it knows its own act, since sense knows itself to be sensing. He holds the same in II de Anima, according to the division of the Commentator, in his exposition of text 138 ⁶.

3. For the clarification of this point, it must be considered, from the doctrine of Aristotle in book II of De Anima—and this is the mind of the Philosopher, text 149 ⁷—that all the particular senses take their origin from one common root, and to that root all the changes of the particular organs are terminated: which root, because it is the common principle and common end of all the particular senses, is called the common sense. Hence it comes about that the common sense, insofar as it is continued with sight and terminates the change of sight, is called sight; but insofar as it terminates the change of the sense of hearing and is continued with hearing, it is called hearing; and so with the others, so that, inasmuch as it completes and terminates the sensible changes of all the senses, it likewise in a way acquires the names of each of the individual senses.

We can therefore take the particular sense in two ways: in one way, for the common sense, insofar as it has continuity with the particular sense, on account of which the particular sense, for instance sight, sometimes receives that name; in another way, for the particular sense itself considered in itself, as distinguished from the common sense.

4. If we take the particular sense in the first way, then the sense senses itself sensing. For since the common sense, as the principle of sight and the terminus of vision, is called sight, we say that sight sees itself seeing: namely, as regards that it is, but not in that it knows the quiddity of vision. And in this way St. Thomas understood the matter, in the passages cited, when he said that the sense knows itself to sense. To this sense the Commentator spoke, II de Anima, text 139 ⁸, that the senses, that is, sensations, move the powers just as sensible things outside move the senses: for by "powers" he understands the common sense as continued to the particular senses. And similarly the ancient expositors are to be understood as saying that the sense senses itself sensing. Hence at the end of the exposition of text 138 ⁹, St. Thomas says that the power by which we see that we see is not extraneous to the visual power, but differs from it by reason. This I understand thus: not that the cognitive power of vision is entirely the same in reality with the sight which is the particular sense, and is distinguished only by the work of the intellect; but because such a power, although it is distinguished in reality and by subject from the particular sight, nevertheless as regards its operation and as regards its power of sensing, has a certain continuity and connection with it, inasmuch as it is the common root of the particular senses and the common terminus of all sensible alterations; and consequently it is distinguished from the particular sight as a root from a branch, and as the principle and end of a line is distinguished from the line. For just as, although the point which is the principle or end of a line is another entity than the entity of the line, it is not nevertheless so extraneous to the line as to have nothing to do with the line—indeed it is something of it, namely its principle or end—so, although the common sense, to which it belongs to know the actions of the proper senses, is a power really distinct from the particular sight and having another organ, since one is in the first cell of the head, the other in the eyes; it is not nevertheless entirely extraneous to sight, indeed it is its root, or principle and origin, and also its end and terminus as regards alteration. And this St. Thomas calls being distinguished from another by reason, in this passage: namely, not to be entirely extraneous to another, but to be something of it, in the way in which we would say that a point is distinguished from a line by reason.

5. But if we take the particular sense in the second way, then the sense does not perceive itself perceiving. And it is in this way that St. Thomas takes the sense at this place.

V. That this response accords with the mind of St. Thomas is evident from what he says in the First Part, q. 78, a. 4, ad 2. For he says that the intentions of the senses are perceived by the common sense, as when someone sees that he sees. He then adds: "For this cannot be done by a proper sense, which knows only the form of the sensible thing by which it is altered, in which alteration vision is completed; and from which alteration there follows another alteration in the common sense, which perceives the vision." — Aristotle must be understood in a similar way in On Sleep and Waking ¹⁰, where he says that sight does not see itself seeing. We can also know from this that this is the mind of St. Thomas, indeed of Aristotle himself, because Aristotle investigates the common sense from this twofold operation, namely from the cognition of the acts of the proper senses, and from the cognition of the diversity of objects belonging to different particular senses, as is clear in the exposition of St. Thomas and of the Commentator there ¹¹, and also at commentary 136. For this would not occur unless those operations were excluded from the particular senses, and therefore it is necessary to find another sense besides those very senses to which these things belong.

VI. But against this solution a doubt arises. Because in the Questions on Truth ¹², where Saint Thomas says that sense senses itself sensing, he adds that this does not happen except through a certain return, albeit incomplete and imperfect. Now if it were not the particular sense but the common sense that knew the act of sense, then sight or another sense would not be said to return to itself: for such a return occurs only through cognition of one's own act after cognition of one's own object, as appears there. Therefore, when Saint Thomas says that sense senses itself sensing, he is not taking "sense" to mean the common sense continued to the particular sense, as the response says. It is answered that, according to the response given, sense is also said to return to itself imperfectly. For, since the common sense perceives the act of the particular sense only insofar as it is something of it and insofar as it has continuation with it, what belongs thus to the common sense can also be said of the particular sense. Hence, because it knows the act of sight, it can be said that sight sees itself seeing, and consequently returns to itself—not because sight, strictly taken, has an act by which it knows its own vision, but because that which is something of it, insofar as it is something of it, has the act by which it knows the vision.

VII. Fifth ¹³. The sense is corrupted by an excessively powerful sensible object; but the intellect is not corrupted by an excessively intelligible object—indeed, one who understands greater things can afterward understand lesser things all the better. Therefore, and so on. How the sense is corrupted by the excess of a sensible object was shown above in this second book, chapter LV ¹⁴.