Commentaria in Summam contra Gentiles, Liber II

After Saint Thomas determined concerning the immaterial object of the cognition of the separate substances, he now determines concerning its material object¹. And first, concerning the universal object; second, concerning the particular object, in the following chapter.

On the first point he does two things: first, he determines the material object; second, he raises a certain doubt².

I. As to the first, the following conclusion is proposed: By the aforementioned intelligible forms, a separate substance knows not only other separate substances but also the species of corporeal things.

The first is proved. Under intelligible being are also contained the species of corporeal things. Therefore a separate substance knows material things. — The consequence is proved. Because, since the intellect of separate substances is perfect by a natural perfection, its object, namely intelligible being, must be comprehended universally.

Note that the foundation of this argument is that, because the intellect is by nature meant to be informed by some likeness of all the contents falling under its formal object, since cognition comes about only by means of a likeness; therefore, since the intellect of a separate substance is not in potency to any intelligible species of those things it can naturally know, but possesses them all in act; and since the intelligible is its formal object; it must have within itself the species of all intelligibles, and thus can understand every intelligible, even material ones, through the species by which it is in act.

II. Second. Separate substances are above corporeal substances. Therefore they are in them in some way. Therefore intelligibly. — The first consequence is proved: because what is contained in a lower species is contained in some way in the higher, as is evident in numbers. — The second is also proved: because what is in something is in it according to the mode of that in which it is.

Note that Saint Thomas did not say simply and absolutely that what is in the inferior species is contained in the superior, but added, in a certain way. For it is not universally required that, according to the substance of the superior, the inferior species be contained in the superior perfectly with respect to all things belonging to it, since by its proper difference the inferior is distinguished from it; but it must be contained in the superior in some manner. For among things of the same order, what is of a lower grade is contained in what is of a higher grade insofar as in the inferior there is some participation of the superior: as in black there is some participation of white, insofar as it participates something of light, which is formal in it. But among things of different orders, those of the lower order are contained in those of the higher order perfectly and totally according to some esse, though not according to the same mode of being: as corruptible bodies are contained virtually in incorruptible bodies, but incorruptibly; and all creatures are contained in God both incorruptibly and immaterially. Since therefore the separate substances are of a higher order than corporeal things, it is necessary that corporeal things be in them according to the mode of separate substances: namely, that they be in them intelligibly, just as they themselves are intellectual substances. And thus they are said to be in a certain way in them: because according to the mode of those separate substances themselves, but not according to the mode of the corporeal things themselves.

III. Third. Separate substances cause the things that come to be through the motion of the heavenly bodies, by moving those bodies themselves. Therefore they know all bodies. — The antecedent is evident, because whatever proceeds from the motion of the heavenly bodies is attributed to those heavenly bodies as instruments, but to the separate substances that move them as principal agents. — The consequence is also evident, because they act through intellect. Hence they know the species and natures of generable and corruptible things as the natures of their proper effects, but the species of the heavenly bodies as the natures of their own instruments. — It is confirmed by the authority of Boethius in the Book on the Trinity, book I, chapter III³.

From this corollary it is concluded that every [separate] substance must know all material things and the whole order of them. This is clear from what has been said. For each of them has the power to comprehend all the species and differences of being; and their intellect has in act all the similitudes to which it is in potency.

IV. As to the second⁴, one could argue against this conclusion as follows: the intellect in act is the thing understood in act; yet it seems unfitting that a material thing should be the perfection of a separate substance.

But Saint Thomas responds that it is not unfitting that a material thing, existing immaterially according to its likeness in the intellect of a separate substance, should be that substance's perfection, just as its proper form. For the thing understood is the perfection of the one understanding in virtue of the likeness of itself which it has in the intellect. For the stone which is outside the soul is not the perfection of our possible intellect.

Note that when it is said that the stone, which exists outside the soul, is not a perfection of our intellect, this can be understood in two ways. In one way, that the quiddity of the stone existing outside the soul is not absolutely in the intellect. And thus Saint Thomas does not intend it. For it was said in the preceding chapter⁵ that the likeness in the soul, and the thing outside the soul represented by it, are of the same ratio, and are one and the same quiddity.

In another way, that it is not in the intellect according to the material esse it has outside the soul. And this is what he means. Hence, after those words he adds: the likeness of a material thing is in a separate substance immaterially, according to the mode of a separate substance, not according to the mode of a material substance, as if he wished to say: Although a thing is said to perfect the intellect by reason of its likeness, inasmuch as in the intellect there is the very quiddity of the thing existing outside the intellect, nevertheless that quiddity is not in the intellect according to its material esse, but according to an immaterial and intelligible esse, so that it, having an immaterial esse in the intellect, represents itself as having a material esse outside the intellect, and it perfects the intellect according to its immaterial esse.