Chapter 52 — That in created intellectual substances there is a difference between being and what is

Now, although intellectual substances are not corporeal, nor composed of matter and form, nor existing in matter as material forms, we must not think that they equal the divine simplicity. For a certain composition is to be found in them from that “being” in them is not the same as “what is.’

For if being is subsistent, nothing besides being is added to it. For even in those things whose being is not subsistent, that which is in an existing thing beside its being is indeed united to the existing thing, but it is not one with its being, except accidentally, insofar as there is one subject having being and that which is beside being: thus it is clear that in Socrates, beside his substantial being, there is white, which is distinct from his substantial being, since to be Socrates and to be white are not the same, save accidentally. Consequently, if being is not in a subject, there will remain no way in which that which is beside being can be united to it. Now being, as being, cannot be diverse, but it can be differentiated by something beside being: thus the being of a stone is other than the being of a man. Hence that which is subsistent being can be one only. Now it was shown above (Bk. 1, ch. 22.) that God is his own subsistent being: hence nothing beside him can be its own being. Therefore, in every substance beside him, the substance itself must be distinct from its being.

Moreover. A common nature, if considered in the abstract, can only be one—although those that have that nature may be found to be many. For if the nature of animal subsisted as separate by itself, it would not have the things belonging to a man or to an ox. Now if we remove the differences which constitute a species, there remains the nature of the genus without division, since the same differences which divide the genus constitute the species. Accordingly, if being itself is common like a genus, a separate self-subsistent being can only be one. If, however, it be not divided by differences as a genus is, but by the fact that it is the being of this or that (as it is in truth), it is yet more evident that what exists of itself can only be one. It follows, therefore, since God is subsistent being, that nothing beside him is its own being.

Again. There cannot possibly be a twofold being absolutely infinite, for being that is absolutely infinite contains every perfection of being, so that if two things had such an infinity, there would be nothing in which they differed. Now subsistent being must be infinite, because it is not limited by any recipient. Therefore, there cannot be any subsistent being outside the first.

Again. If there is a self-subsistent being, nothing is applicable to it except that which belongs to a being as being. This is so because what is not said of a thing as such is only applicable to it accidentally, by reason of the subject: so that if we suppose it to be separated from its subject, it is in no way applicable to it. Now to be caused by another is not applicable to a being, as being: otherwise every being would be caused by another, and consequently we should have to proceed to infinity in causes, which is impossible, as shown above. (Bk. 1, ch. 13.) Therefore, that being which is subsistent must not be caused. Therefore, no caused being is its own being.

Moreover. The substance of a thing appertains to it of itself and not by another: therefore, to be actually lightsome is not of the air’s substance, since it comes to it from something else. Now every created thing has being from another, else it would not be caused. Therefore, in no created being is its being the same as its substance.

Again. Since every agent acts insofar as it is actual, it belongs to the first agent, which is most perfect, to be actual in the most perfect way. Now a thing is the more perfectly actual, the more its act is posterior in the order of generation, for act is posterior in time to the potency in the one and same subject which passes from potency to act. Also, act itself is more perfectly actual than that which has act, for the latter is actual on account of the former. Accordingly, these premises being supposed, it is clear from what has been already proved (Bk. 1, ch. 13.) that God alone is the first agent. Therefore, it belongs to him alone to be actual in the most perfect way—that is, to be the most perfect act. Now this is being, in which generation and all movement terminates, since every form and act is in potency before it acquires being. Therefore, it belongs to God alone to be his own being, just as it belongs to him alone to be the first agent.

Moreover. Being itself belongs to the first agent in respect of his proper nature: for God’s being is his substance, as we have proved above. (Bk. 1, ch. 22.) Now that which belongs to a thing in respect of its proper nature does not belong to others except by way of participation (like heat to bodies other than fire). Therefore, being itself belongs to all others except the first agent by a kind of participation. But that which belongs to a thing by participation is not its substance. Therefore, it is impossible that the substance of a thing other than the first agent should be being itself.

Hence the name proper to God is stated in Exodus 3:14 to be “he who is,” because it is proper to him alone that his substance is not distinct from his being.