Commentaria in Summam contra Gentiles, Liber II

It has been shown with effective arguments that the position, indeed the fiction, of Averroes is impossible. Now, since Averroes strove to confirm his fiction with the sayings of Aristotle, Saint Thomas proves that it is also against the mind of Aristotle ¹, with many sayings of Aristotle himself.

I. And first he argues as follows ². Aristotle defines the soul as the first act of a physical organic body having life in potency; and he says that this definition, stated universally, applies to every soul—not speaking under doubt, as Averroes feigns, as is clearly evident from the Greek text and Boethius's translation. Indeed, he wishes it to be extended to the intellect: as is clear from the fact that in the same chapter he adds, saying of the soul he had defined that it has certain separable parts—which can be understood of nothing other than the intellect. Therefore the intellect is not a separate substance.

If it is said that this definition does not apply to every soul except equivocally, and that Aristotle shows this when he adds, "But concerning the intellective and the perspectival power nothing is yet manifest," the reply is that by these words the Philosopher does not wish to exclude the intellect from the common definition of soul, but from the proper natures of the other parts; just as one who says that one genus of animal is winged as opposed to walking does not take away from the winged animal the common definition of animal. Hence Aristotle also adds, "And this alone is capable of being separated, as the everlasting from the corruptible." From these words it is clear that he holds the intellect to be other than the other parts of the soul on account of its everlastingness, which does not belong to the others; but it is not his intention, as Averroes imagines, that it has not yet been declared whether the intellect is a soul, as with the other principles—since the old text does not read "nothing is declared," or "nothing is said," but "nothing is manifest," namely with respect to what is proper to the intellect, not with respect to the common definition of soul. Moreover, if "soul" were said equivocally of the intellect and the others, Aristotle would first have distinguished the equivocation, as is his custom, so as not to proceed in an equivocation, which is unbecoming in demonstrative sciences. ³nothing is declarednothing is saidnothing is manifest

This reasoning, taken from the words of Aristotle, Saint Thomas explains more fully in the Book which he published against the Averroists ⁴. But since he says that from the Greek text it is to be held that Aristotle speaks not doubtfully but assertively in his definition of the soul, it must be noted that before those words of text 7, where it is said, If, however, something common to every soul must be stated etc., in text 6 the Philosopher had spoken absolutely, defining the soul: Διὸ ψυχή ἐστιν ἐντελέχεια ἡ πρώτη σώματος φυσικοῦ ζωὴν ἔχοντος δυνάμει, which words Boethius interprets thus: Whence the soul is the first act of a physical body having life in potency. But in text 8 he says, καθόλου μὲν οὖν εἴρηται τί ἐστιν ἡ ψυχή, which Boethius interprets: Universally, then, it has been said what the soul is. In these passages it is evident that the Philosopher handed down the definition of the soul not doubtfully but assertively; and that he used a mark of conditionality not because he doubted, but so that, proceeding from the supposition of the antecedent, he might conclude a brief definition of the soul, in place of what he had said having life in potency, by putting organic.

It must also be noted that when Saint Thomas says that Averroes badly interprets Aristotle where he says, But concerning the intellect and the power of vision nothing is yet manifest, this is because the old translation has it so, as Saint Thomas cites it. For the Greek text also reads thus: οὐδέπω φανερόν, that is, it is not yet manifest. Hence it is not the Philosopher's meaning that nothing had yet been said or declared about the intellect, namely whether it is a soul; rather, he enumerated the intellect among the parts of the soul, and he wished the definition of soul to be common even to the intellectual soul. But what he meant was that what is proper to the intellect, by which it is distinguished and separated from the other parts of the soul, is not yet manifest from those things; as is clear from the words immediately following, where he says, But another kind of soul seems to be this, and this alone to admit of being separated, as the perpetual from the corruptible. For since it is a part of the soul, it is distinguished from the others in reason, as the perpetual from the corruptible.

II. But from the words of Themistius, in On the Soul, chapter XXIII ⁵, one might answer these objections as follows: since the rational soul is twofold—namely, one kind is conjoined, which gives man his being and his species, and is corruptible; the other is separate, which Themistius calls abiding without; just as the perfection of what is transparent is twofold, namely the sun and light—Aristotle seeks a definition common to every soul that gives being, and this per se and first; but not a definition common to the soul extrinsically. It is nevertheless true that he sometimes interposes something about that separate soul: for it seems to him and to others that in some way one definition applies to both, though analogically.

A twofold sign of this is taken from Aristotle's words. First, because, when he had arrived at the end of the first and most common definition, he adds, as something manifest, ⁶ that certain species of soul are the act of a body and certain are not. This could not be if that definition belonged univocally to every soul; for it is manifest that everything to which that definition belongs is the act of a body. And therefore it belongs per se and in the first instance only to the soul joined to a corruptible body.

The second reason is that Aristotle adds there ⁷: Further, it is unclear whether the soul is the act of the body as the sailor is of a ship. Now he does not doubt this concerning souls united to bodies, but concerning the separated soul. And thus it appears that conjoined souls and the separated soul are not act in the same way: and for that reason that definition is said equivocally, as the Commentator held. Hence he immediately adds: Therefore, in a figurative way, let the soul be so determined and described—that is, not determining how many souls there are, or whether that definition applies to them univocally.

III. But against the principal statement of this response, namely, that the soul conjoined, which is corruptible, is defined first and per se: yet that he sometimes interposes concerning the separated soul, because the definition of soul belongs to it in a certain way, in an analogous mode, an objection is raised. For Aristotle, wishing to prove that the soul is the act of the body, in text 24 ⁸, argues thus: The soul is that by which first we live, sense, are moved, and understand. Therefore it is an act. According, therefore, to the mind of Aristotle, the soul which he defined, and of which he proves that definition, is the principle by which first we understand. But this is not the conjoined soul which you say is corruptible, namely the cogitative, because it is not through it that we first understand, although it somehow concurs in our understanding: but it is the soul having intellect, since he himself in III de Anima ⁹, speaking of the possible intellect, says: Now by intellect I mean that by which the soul opines and understands. Therefore that definition was not given of the corruptible soul alone, but also of the incorruptible, which is truly intellective.

Furthermore, dividing the powers of the soul which he had defined, in text 27 ¹⁰, he says: But we call the powers of the soul the vegetative, the sensitive, the appetitive, the motive with respect to place, and the intellective. Therefore the intellective is a power of the soul which he had defined. Therefore he did not define only the corruptible soul.

If it is said that by intellectivum he means the cogitative power: it is argued against this. Because further on, in text 29, ¹¹, wishing to show how all the aforementioned powers belong to certain beings, he concludes: But in some there is also the motive power by place, while in others the intellective and the intellect, as in men, where it is clear that he also explains intellectivum as meaning intellect. For there too Averroes, in commentary 29, ¹², says: And let us also take as evident that the cogitative power and the intellect exist in other modes in animals.

2. To the first sign brought forward, it is answered first. If it be granted that Aristotle is speaking of the species of soul (which is nevertheless false), it is said that he speaks of act as dependent on matter in its esse. For since some soul depends on matter in its esse, as being educed from the potency of matter, therefore it is not separable from the body. But another soul, because it is not an act educed from the potency of matter, and hence does not depend on matter in its esse, as is the intellective soul, is separable from the body. Yet with this it stands that every soul is univocally an informing act of matter; and thus the definition of soul is univocally common to all souls.

It is said second, that the Philosopher speaks there of the parts of the soul that are potestative, which are its powers. This is evident from the fact that he raises as a question whether the soul has parts. For there is no doubt whether it has subjective parts and species; but there is indeed doubt whether it has potential parts, since concerning each one it is doubtful whether it is a soul or a power of the soul ¹³.

It is said third, that the authority of the Philosopher favors our position more than the opposite. For when he says that certain powers of the soul, which he had defined, are not the act of the body, that is, are not affixed to any determinate organ, it follows that the intellective soul also, whose power is the intellect, is comprehended under that definition of the soul.

3. To the second sign it is said that the Philosopher does not introduce that doubt because he doubts whether the intellective soul is an informing act, while he does not doubt concerning the soul joined to a corruptible body; but because, having said absolutely ¹⁴ that the soul is the act of the body — which he himself understood of an informing act, as is clear from what he said, ¹⁵ that one need not ask how from soul and body there comes to be one thing; and from what he said ¹⁶ that the soul is a substance according to reason and what-it-was-to-be — he had not yet perfectly explained how it was an act: namely, whether in the manner in which a mover can be called the act of the thing moved, or in the manner in which form is the act of matter; and therefore it was not yet fully manifest whether the soul was united to the body as a sailor to a ship, or in some other way. And so he said, "Let the soul be determined and described thus figuratively": namely, because he had not yet shown the truth exactly and clearly; not because the definition of soul would not apply univocally to every soul. Hence, in order to exclude this objection, which arises from Plato's opinion, he shows from the operations of the soul, of which it itself is the principle, ¹⁷ that it is not united to the body as a sailor to a ship, but as form to matter: since that by which something first operates is its form; but the soul is the first thing by which we live, sense, are moved, and understand ¹⁸; therefore it must be the act and form of the body. And thus he shows that it has been plainly declared that the soul which he had said to be the act of the body is an act in the manner of informing, and not merely in the manner of moving.

IV. Second, ¹⁹ Saint Thomas argues principally from the words of the Philosopher. The intellect is a power of the soul. Therefore it is not a separate substance. — The antecedent is proved. First, because the Philosopher enumerates the intellect among the powers of the soul. Second, because in text 21 he calls the visual power a power.

Third. The intellect is a part of the soul, as is clear from the beginning of Book III of the De Anima ²⁰, where it is said: "But concerning that part of the soul by which the soul knows and understands." Therefore, and so on.

Fourth. The intellect is that by which the human soul understands. Therefore, etc. — The consequence is evident, because that by which something first operates must be its form, as is clear from what was said above ²¹ — The antecedent, however, is proved from On the Soul III, text 5, where the Philosopher says: I mean by intellect that by which the soul opines and understands.

Saint Thomas explains these arguments more fully in the Treatise against the Averroists ²². Therefore they are required there.