Thomas Aquinas - Summa Theologica, Part I (Prima Pars)

Reply Obj. 3: "Many" is taken in two ways: absolutely, and in that sense it is opposed to "one"; in another way as importing some kind of excess, in which sense it is opposed to "few"; hence in the first sense two are many but not in the second sense.

Reply Obj. 4: "One" is opposed to "many" privatively, inasmuch as the idea of "many" involves division. Hence division must be prior to unity, not absolutely in itself, but according to our way of apprehension. For we apprehend simple things by compound things; and hence we define a point to be, "what has no part," or "the beginning of a line." "Multitude" also, in idea, follows on "one"; because we do not understand divided things to convey the idea of multitude except by the fact that we attribute unity to every part. Hence "one" is placed in the definition of "multitude"; but "multitude" is not placed in the definition of "one." But division comes to be understood from the very negation of being: so what first comes to mind is being; secondly, that this being is not that being, and thus we apprehend division as a consequence; thirdly, comes the notion of one; fourthly, the notion of multitude. _______________________

THIRD ARTICLE [I, Q. 11, Art. 3]

Whether God Is One?

Objection 1: It seems that God is not one. For it is written "For there be many gods and many lords" (1 Cor. 8:5).

Obj. 2: Further, "One," as the principle of number, cannot be predicated of God, since quantity is not predicated of God; likewise, neither can "one" which is convertible with "being" be predicated of God, because it imports privation, and every privation is an imperfection, which cannot apply to God. Therefore God is not one.

On the contrary, It is written "Hear, O Israel, the Lord our God is one Lord" (Deut. 6:4).

I answer that, It can be shown from these three sources that God is one. First from His simplicity. For it is manifest that the reason why any singular thing is "this particular thing" is because it cannot be communicated to many: since that whereby Socrates is a man, can be communicated to many; whereas, what makes him this particular man, is only communicable to one. Therefore, if Socrates were a man by what makes him to be this particular man, as there cannot be many Socrates, so there could not in that way be many men. Now this belongs to God alone; for God Himself is His own nature, as was shown above (Q. 3, A. 3). Therefore, in the very same way God is God, and He is this God. Impossible is it therefore that many Gods should exist.

Secondly, this is proved from the infinity of His perfection. For it was shown above (Q. 4, A. 2) that God comprehends in Himself the whole perfection of being. If then many gods existed, they would necessarily differ from each other. Something therefore would belong to one which did not belong to another. And if this were a privation, one of them would not be absolutely perfect; but if a perfection, one of them would be without it. So it is impossible for many gods to exist. Hence also the ancient philosophers, constrained as it were by truth, when they asserted an infinite principle, asserted likewise that there was only one such principle.

Thirdly, this is shown from the unity of the world. For all things that exist are seen to be ordered to each other since some serve others. But things that are diverse do not harmonize in the same order, unless they are ordered thereto by one. For many are reduced into one order by one better than by many: because one is the per se cause of one, and many are only the accidental cause of one, inasmuch as they are in some way one. Since therefore what is first is most perfect, and is so per se and not accidentally, it must be that the first which reduces all into one order should be only one. And this one is God.

Reply Obj. 1: Gods are called many by the error of some who worshipped many deities, thinking as they did that the planets and other stars were gods, and also the separate parts of the world. Hence the Apostle adds: "Our God is one," etc.

Reply Obj. 2: "One" which is the principle of number is not predicated of God, but only of material things. For "one" the principle of number belongs to the genus of mathematics, which are material in being, and abstracted from matter only in idea. But "one" which is convertible with being is a metaphysical entity and does not depend on matter in its being. And although in God there is no privation, still, according to the mode of our apprehension, He is known to us by way only of privation and remotion. Thus there is no reason why a certain kind of privation should not be predicated of God; for instance, that He is incorporeal and infinite; and in the same way it is said of God that He is one. _______________________

FOURTH ARTICLE [I, Q. 11, Art. 4]

Whether God Is Supremely One?

Objection 1: It seems that God is not supremely one. For "one" is so called from the privation of division. But privation cannot be greater or less. Therefore God is not more "one" than other things which are called "one."

Obj. 2: Further, nothing seems to be more indivisible than what is actually and potentially indivisible; such as a point and unity. But a thing is said to be more "one" according as it is indivisible. Therefore God is not more one than unity is one and a point is one.

Obj. 3: Further, what is essentially good is supremely good. Therefore what is essentially one is supremely one. But every being is essentially one, as the Philosopher says (Metaph. iv). Therefore every being is supremely one; and therefore God is not one more than any other being is one.

On the contrary, Bernard says (De Consid. v): "Among all things called one, the unity of the Divine Trinity holds the first place."

I answer that, Since one is an undivided being, if anything is supremely one it must be supremely being, and supremely undivided. Now both of these belong to God. For He is supremely being, inasmuch as His being is not determined by any nature to which it is adjoined; since He is being itself, subsistent, absolutely undetermined. But He is supremely undivided inasmuch as He is divided neither actually nor potentially, by any mode of division; since He is altogether simple, as was shown above (Q. 3, A. 7). Hence it is manifest that God is one in the supreme degree.

Reply Obj. 1: Although privation considered in itself is not susceptive of more or less, still according as its opposite is subject to more or less, privation also can be considered itself in the light of more and less. Therefore according as a thing is more divided, or is divisible, either less or not at all, in the degree it is called more, or less, or supremely, one.

Reply Obj. 2: A point and unity which is the principle of number, are not supremely being, inasmuch as they have being only in some subject. Hence neither of them can be supremely one. For as a subject cannot be supremely one, because of the difference within it of accident and subject, so neither can an accident.

Reply Obj. 3: Although every being is one by its substance, still every such substance is not equally the cause of unity; for the substance of some things is compound and of others simple.

As hitherto we have considered God as He is in Himself, we now go on to consider in what manner He is in the knowledge of creatures; concerning which there are thirteen points of inquiry:

(1) Whether any created intellect can see the essence of God?

(2) Whether the essence of God is seen by the intellect through any created image?

(3) Whether the essence of God can be seen by the corporeal eye?