Commentaria in Summam contra Gentiles, Liber II

After St. Thomas has determined those things that positively and affirmatively belong to intellectual substances, he consequently determines those things that are excluded by their nature ¹. In regard to this, however, he does two things: first, he removes from them materiality with respect to substance considered in itself; second, the materiality that arises from dependence on matter, in chapter LI. And because wherever matter is found, continuous quantity is also found, therefore, so that he may proceed from what is more known to us, he first shows that these substances are not a body; second, that they are not composed of matter and form, in the following chapter.

I. As to the first, the following conclusion is proposed: No intellectual substance is a body.

It is proved first. The intellect does not comprehend any thing understood by the measure of quantity: since it understands itself wholly, and comprehends both the whole and its parts. Therefore no thinking substance is a body. — The consequence is proved: because no body contains another except by the measure of quantity.

But this argument does not seem to be effective. For by means of it it would likewise be proved that man is not a body: because by his intellect he does not comprehend anything according to the measure of quantity.

It is answered that, from the fact that the intellect comprehends nothing quantitative, it is argued that a substance which is wholly intelligent in itself, which is properly called an intellectual substance, is not a body; but not of a substance that is intelligent only by a part, as if composed of an intellectual and a bodily substance, such as man. Therefore the objection is not against the intended point.

II. Second. The intellect receives the substantial forms of all bodies, and yet it is not corrupted but perfected, since it understands by means of them. Therefore etc. — The consequence is proved. For no body can receive the substantial form of another body unless it loses its own form through corruption.

But someone might reply to this argument that the forms of bodies are not received in the intellect insofar as they are substances, but insofar as they are accidents. And thus the argument does not follow.

It is answered that, since the substantial form of a body existing in matter is of the same rational character as itself existing in the intellect, although it has another and another mode of being, as will be shown in what follows ², and in matter it is a substance, while in the intellect it is an accident; therefore it can be said absolutely that the substantial form of a body is received in the intellect, even though in the intellect it does not have substantial esse. But a body by no means receives the substantial form of another body: therefore it cannot be said absolutely that it receives the substantial form of another body. The foundation of the argument, then, is that a body by no means receives the substantial form of another body: but the intellect, speaking absolutely, receives the forms of bodies, although they are received according to spiritual and immaterial esse, on account of the condition of the intellect receiving them.

III. Third. Whatever is received into a body is received into it according to the division of quantity. Therefore a form is not received into a body except as individuated. Therefore, if the intellect were a body, the intelligible forms of things would be received in it as individuated. Therefore it would understand only particulars. — This consequent is false. Therefore etc. — The first consequence is proved: because the principle of the diversity of individuals of the same species is the division of matter according to quantity. — The last is also proved: because the intellect understands things through their forms, which it has within itself.

2. Concerning the last consequence adduced here, a doubt is raised. For the form that is in this intellect, according to the truth of the thing, is individual and singular, numerically distinct from the form of the same ratio existing in another intellect. And yet by means of it the intellect understands the universal. Therefore that consequence is false.

3. For the clarification of this, it must be considered that, since a material nature existing in the intellect is a material nature—existing, that is, of the same account as the nature which is outside the intellect—and has in the intellect an immaterial and intelligible esse, as it were the accident and form of that nature itself: it is placed in a twofold order of things, namely in the order of intelligibles on the side of its mode of being (essendi), and in the order of material things on the side of its account. By way of example, the nature of stone existing in the intellect has that it is the intelligible species of the intellect and its intellectual accident; and it has that it is the nature of stone. If it be considered as it is in the order of intelligibles, or as it is the intelligible form of one intellect, thus it is individual and singular: for it has an esse distinct from another intelligible species of the same account existing in the intellect of another; for accidents of the same account are distinguished numerically and individually by the numerical distinction of the subjects in which they are. But if it be considered as it is a material nature of the same account as the form represented by it which is in matter, thus it is not individual or singular, but is universal and abstract and unlimited: for it is not the form of this or that stone, having a material esse determined to here and now as the form of this stone has; but it is the form of stone absolutely and abstractly; or rather, it is not this or that stone, but is absolutely stone having an immaterial esse; and it is not distinguished from other particular stones as one particular stone from another, but as the nature taken universally and absolutely from the singulars of that nature. Hence the esse of that nature, if it be considered as the esse of an intelligible form, is the esse of an individual and singular thing; but if it be considered as the esse of the nature of stone, it is universal and unlimited; just as if whiteness were separated from every subject, it would not be this or that whiteness, but would be absolutely whiteness, although it would be one being distinct from every other whiteness.

Nature, therefore, existing in the intellect and considered according to its ratio insofar as it is such a form, is not individual and singular, because it is no more this singular form than that one; rather, it is absolutely and without limit such a form. But insofar as it is an accident of the intellect, as its intelligible form, it is individual and singular. And since such a species represents the form which exists outside, insofar as it is of the same ratio with it—in which way we said it is universal—but does not represent the individuating matter, therefore through it the intellect knows the universal first and per se, as through what is first represented by it, but not the singular except secondarily and indirectly. Yet because it is a principle for eliciting intellection insofar as it is the form of the intellect—in which way we said it is singular and individual—therefore the intellection elicited through it is individual and singular, numerically distinct from another intellection of the same species.

To the argument, therefore, it is said that the form existing in our intellect is not individuated and singular as it is in the order of material things according to its nature, but is universal. Therefore it is not necessary that through it the intellect know only the singulars of that nature. But if the intellect were a body, the form received in it would be individual and singular, like the form of this stone: for a body receives only individually and materially. Therefore the intellect would know through it only particulars. And thus the consequence holds, on the supposition that the intellect is a body; but it does not hold if we suppose it to be incorporeal.

IV. Fourth. The intellect would not understand anything except bodies, because nothing acts beyond its own species (that is, by its own power; but it does so well as the instrument of another). But this is false, because we understand many things that are not bodies. Therefore, and so on.

Fifth. An intelligent substance is not an infinite body. For no such thing is given. — Nor a finite one. For the power of the intellect is in some way infinite in understanding: for it understands the species of numbers, figures, and proportions to infinity; and it understands the universal, which is infinite in power according to its scope, since it contains individuals that are infinite in potency. But in a finite body there cannot be an infinite power. — Therefore, etc.

2. But this argument seems not to conclude. For although a simply infinite power cannot be in a finite body, nothing prevents an infinite power in some respect from being in a finite body: for fire has the power of burning infinitely, if combustible material is supplied to it infinitely; and the heavens have the power of generating bodies infinitely. Therefore, notwithstanding that the intellect's power is in some way or in some respect infinite, the intellect could be a finite body.

It is answered that the quantity of a power, considered in respect of its object, is measured according to the magnitude of the object: so that the power which can extend to a greater object is greater; and the power is infinite which can extend to an infinite object—simply infinite, indeed, if it can extend to what is simply infinite; but infinite in a qualified sense if it can extend to what is infinite in a qualified sense. And therefore the intellect's understanding of numbers to infinity argues an infinite power in a qualified sense, inasmuch as the intellect apprehends no number so great that it cannot apprehend a greater; and likewise its understanding of the universal, because the universal contains infinitely many things at once; for this is the object of the intellect as being of a magnitude and perfection in some way infinite.

I say, therefore, that the power of fire is not infinite in a qualified sense according to perfectional quantity, nor is the power of the sun: for although they can act upon things infinite in number, they cannot act upon things infinite in species; and the infinity of objects in number does not show an infinite magnitude of power, since the least power, if it endures perpetually, can produce effects infinite in number. But the intellect can act upon things infinite in species: for the augmentation of numbers into infinity is according to species. And likewise the universal is in a way infinite according to species: insofar as of itself it is not limited to this or that singular, but signifies something unlimited within its species, into which the intellect can enter of itself, and not only as found in singulars. And therefore from the fact that the intellect can act upon these infinite objects, it is excellently shown that it is of a power and perfection somehow infinite intrinsically, and not merely extrinsically.

V. Sixth. Two intellects contain and comprehend one another: while one understands the other. But not two bodies: since a containing body exceeds what is contained. Therefore, etc.

Seventh. The intellect reflects upon itself in acting. Therefore, etc. — The consequence is proved. For the action of no body is reflected back upon the agent, since it was shown in the Physics that no body is moved by itself except according to a part.

Eighth. The intellect understands itself understanding. Therefore etc. — The consequence is proved: because the act of a body is not terminated at an action, nor motion at motion.

It is confirmed. For Sacred Scripture names intellectual substances spirits, in the way it is accustomed to name God incorporeal, according to that passage John IV: God is a spirit; for it is said in Wisdom VII: For she is in her etc.

By this is excluded the error of the ancients, who held that no substance exists except a corporeal one, and of certain Christians who say that the soul is a body figured forth.