Commentaria in Summam contra Gentiles, Liber II

Having shown that intellectual substances are not bodies, it remains to be shown that they are not composed of matter and form ¹.

I. And this conclusion is posited: Intellectual substances are immaterial.

It is proved, first, as follows. No intellectual substance is a body. Therefore none is composed of matter and form. — The consequence is proved. Because everything composed of matter and form is a body: since matter cannot receive diverse forms except according to diverse parts; and it is divided by quantity.

Second. The intellect cannot be composed of matter and an individual form. Therefore an intelligent substance is not composed of matter and form. — The consequence is evident, because just as man is not without this man, so matter is not without this matter. — But the antecedent is proved as follows: because the species of things understood are made actually intelligible by being abstracted from individual matter; and as they are actually intelligible, they become one with the intellect.

On the matter of this argument we have said enough in the first book ² Only one point must not be passed over: since each thing is received in another according to the mode of the receiver, a form cannot become immaterial by being received in something else unless the receiver itself is immaterial — understand, if it is received there according to complete esse and in act: for if it were received incompletely and in becoming, as the power of an agent is received in an instrument and the species of color in the air, as is said in De Veritate, q. xxvii, 4, ad 4, it would not be unfitting for a form to be received immaterially in a material thing. Therefore it follows rightly from the fact that a form actually intelligible, abstracted from matter, becomes one with the intellect, that the intellect too must be immaterial.

II. Third. If this is so, understanding will be of the composite of matter and form. Therefore the intellect will understand neither matter nor form, but only the composite. But this is false. Therefore etc. — The first consequence is proved: because the action of anything composed of matter and form is not of the matter alone or of the form alone, but of the composite. — The second is also proved: because an act is terminated at something similar to the agent.

2. But this argument does not seem to conclude, for two reasons. First, because by it it would be concluded that man understands only the composite. For understanding, since it is an action of man, who is composed of matter and form, will not belong to the form of man alone, but to the composite. And consequently only the composite understands.

Second, because it would follow that matter could in no way be understood. For if, because an act is terminated at what is like the agent, it follows that if what is understood is a composite, only the composite as such is understood; then by the same reasoning it follows that if the one understanding is form alone, only form as such is understood.

3. It is answered that the proposition, The action of the composite from matter and form is not of the matter alone or of the form alone, but of the composite, is understood of a composite from matter and form which is not per se subsistent, but depends in its esse upon matter. For then, since the form does not have per se esse, neither will it have per se operation; rather, the operation will belong only to the composite as to that which operates. But if the composite is constituted by a per se subsistent form, not only will the composite be said to operate, but also the very form itself, with respect to that operation of which the form itself, insofar as it subsists, is the principle: for because such a form has per se esse, therefore it also operates per se. Since, therefore, the form of man is per se subsistent, understanding is not only of man but also of the form itself: indeed, as is said in On Spiritual Creatures, a. 2, ad 2, man is said to understand insofar as the soul, which is his formal part, has this proper operation, just as the operation of any part is attributed to the whole. But if the intellectual were purely and totally composed of matter and form, only the composite itself would be subsistent: and for this reason understanding would be of the composite alone, as the argument concluded. From these things it is clear that the objection brought forward is not against the intention of St. Thomas, and that the argument itself is efficacious.

4. To the second objection it must be said that an action terminates in something like the agent, either according to nature or according to a superadded form by which it acts. If, however, the intellect is not composed of matter and form, then in it there can be likenesses of things received immaterially and universally, and not only of forms but also of matter: whether this be a proper likeness of matter, or one that is the same for the composite and the matter. And since it understands through such likenesses, it will therefore be able to understand not only form but also matter. But if it were composed of matter and form, it would act only either through its own proper nature or through forms received individually and materially, which would represent only the composite materially, but not distinctly the quiddity of matter or of form. Therefore it would understand only the composite, and not matter and form. The argument proceeding from that proposition therefore concludes well that only the composite would be understood if intellectual substance were posited as composed of matter and form; but not if it is posited as a simple and immaterial form.

IV. Fourth. The forms of sensible things have their esse more perfectly in the intellect than in sensible things. Therefore, if the intellect is composed of matter and form, the forms of things understood will make the intellect be of such a nature as that which is understood. Hence there follows the error of Empedocles, namely that the soul knows fire by fire, and earth by earth, and so with the others. — The antecedent is proved: because in the intellect forms are simpler and extend to more things. — The first consequence is also proved: because a form existing perfectly in matter makes a thing to be actually such, namely fire or colored, etc.; but not if it exists in it imperfectly.

It must be noted, concerning the proof of the consequence, that every form received in matter does indeed give actual esse, since it belongs to every form to give esse. But it is true that sometimes the esse which it gives to some matter is not sufficient for the thing to be denominated absolutely as of such a nature as the thing is usually said to have when it has such a form; and sometimes it is sufficient for the thing to be so denominated. For when a form has a diminished and imperfect esse in matter, it does not denominate the possessor of that form as of such a nature: thus, because the form of color in air has an intentional, diminished, and imperfect esse by comparison with its esse in a wall—since there it is present only as in a bearer—it is not said that the air is colored; but in a wall, because it has a fixed and permanent esse, and according to the perfect mode in which color is apt to actuate its material subject, therefore the wall is said to be colored. What Saint Thomas says, then, that a form which is imperfectly in something does not make it to be such is not to be understood as though it gave no esse at all—for otherwise it would not be in it as a form—but that it does not give an esse denominative from such a form, in the way that something is usually denominated absolutely as such from such a form. For since color in air has esse in a more imperfect manner than in its proper matter, being there intentionally and diminutively, it can indeed be said that the air is intentionally colored, but not absolutely colored.

2. But doubt is raised concerning the antecedent of this argument. For the forms of sensible things have accidental esse in the intellect, whereas in their own nature they have substantial esse. Therefore they do not have more perfect esse in the intellect than in things.

It is answered that the esse of a thing can be considered in two ways: namely, with respect to the thing itself, and with respect to the mode. With respect to the thing, substantial esse is always nobler than accidental esse. With respect to the mode, however, some accidental esse is nobler than some substantial esse: just as we say that the accident itself, insofar as it is a form of substance, is nobler than substance itself. Saint Thomas therefore speaks in this passage of esse not with respect to the thing, but with respect to the mode of being: for it is a nobler mode of being to have an immaterial esse unlimited by matter than to have a material and limited esse; even though the limited esse be substantial, while the unlimited and immaterial one be accidental.

V. Fifth. Then the forms of things will be in the intellect materially, just as they are outside it, because each thing is in another according to the mode of the receiver. Therefore they will not be actually intelligible in the intellect, just as they are not outside it. This is false. Therefore, and so on.

Sixth. The forms of contraries are not contraries in the intellect. Therefore in it they do not have material being. Therefore etc. — The antecedent is proved: because one of the contraries is the intelligible reason of the other. — The first consequence is also proved: because according to the being they have in matter, they are contraries and expel one another.

Note that when it is said that one of two contraries is the intelligible reason of the other, the intelligible reason here is not taken for the intelligible species representative of the thing understood, but is taken universally for the form by which the intellect understands something. For thus one contrary is the intelligible reason of the other, insofar as the intellect is led from the cognition of one contrary, through its form, to the cognition of the other contrary as well. Therefore Saint Thomas assigned the reason for his statement, adding: because through one contrary (namely, the one known) the other is known.

Seventh. The intellect is not moved by receiving forms; rather, remaining at rest, it is perfected and understands. Therefore, etc. — The consequence is proved. Because matter does not receive any form except through motion or change.

It must be noted that, if motion is taken for every reception of a form, then the intellect is moved in receiving intelligible species. But if motion is taken as signifying the reception of a form together with the rejection of the contrary form, then the intellect is not moved by receiving the species of things, nor is it changed—by change, namely, that which occurs with the rejection of a preexisting form—as St. Thomas says, III de Anima, lect. XI ³. Matter, however, does not receive a form except through the rejection of the preceding form. Therefore it itself is properly changed in such a reception. And it is of motion so taken that the argument adduced here proceeds.

The conclusion is confirmed by the authority of Dionysius, chapter 4 of On the Divine Names, where he says: "Because of the rays of the divine goodness," etc.