Article 1 — Whether one adds anything to being?

Objection 1: It seems that one adds something to being. For everything is in a determinate genus by addition to being, which penetrates all genera. But one is a determinate genus, for it is the principle of number, which is a species of quantity. Therefore one adds something to being.

Obj. 2: Further, what divides a thing common to all, is an addition to it. But being is divided by one and by many. Therefore one is an addition to being.

Obj. 3: Further, if one is not an addition to being, one and being must have the same meaning. But it would be nugatory to call being by the name of being; therefore it would be equally so to call being one. Now this is false. Therefore one is an addition to being.

On the contrary, Dionysius says (Div. Nom. 5, ult.): Nothing which exists is not in some way one, which would be false if one were an addition to being, in the sense of limiting it. Therefore one is not an addition to being.

I answer that, One does not add any reality to being; but is only a negation of division; for one means undivided being. This is the very reason why one is the same as being. Now every being is either simple or compound. But what is simple is undivided, both actually and potentially. Whereas what is compound, has not being whilst its parts are divided, but after they make up and compose it. Hence it is manifest that the being of anything consists in undivision; and hence it is that everything guards its unity as it guards its being.

Reply Obj. 1: Some, thinking that the one convertible with being is the same as the one which is the principle of number, were divided into contrary opinions.

Pythagoras and Plato, seeing that the one convertible with being did not add any reality to being, but signified the substance of being as undivided, thought that the same applied to the one which is the principle of number. And because number is composed of unities, they thought that numbers were the substances of all things.

Avicenna, however, on the contrary, considering that one which is the principle of number, added a reality to the substance of being (otherwise number made of unities would not be a species of quantity), thought that the one convertible with being added a reality to the substance of beings; as white to man. This, however, is manifestly false, inasmuch as each thing is one by its substance. For if a thing were one by anything else but by its substance, since this again would be one, supposing it were again one by another thing, we should be driven on to infinity.

Hence we must adhere to the former statement; therefore we must say that the one which is convertible with being, does not add a reality to being; but that the one which is the principle of number, does add a reality to being, belonging to the genus of quantity.

Reply Obj. 2: There is nothing to prevent a thing which in one way is divided, from being another way undivided; as what is divided in number, may be undivided in species; thus it may be that a thing is in one way one, and in another way many. Still, if it is absolutely undivided, either because it is so according to what belongs to its essence, though it may be divided as regards what is outside its essence, as what is one in subject may have many accidents; or because it is undivided actually, and divided potentially, as what is one in the whole, and is many in parts; in such a case a thing will be one absolutely and many accidentally.

On the other hand, if it be undivided accidentally, and divided absolutely, as if it were divided in essence and undivided in idea or in principle or cause, it will be many absolutely and one accidentally; as what are many in number and one in species or one in principle. Hence in that way, being is divided by one and by many; as it were by one absolutely and by many accidentally. For multitude itself would not be contained under being, unless it were in some way contained under one. Thus Dionysius says (Div. Nom., cap. ult.) that there is no kind of multitude that is not in a way one. But what are many in their parts, are one in their whole; and what are many in accidents, are one in subject; and what are many in number, are one in species; and what are many in species, are one in genus; and what are many in processions, are one in principle.

Reply Obj. 3: It does not follow that it is nugatory to say being is one; forasmuch as one adds an idea to being.