After the foregoing, we consider the divine unity; concerning which there are four points of inquiry:
(1) Whether "one" adds anything to "being"?
(2) Whether "one" and "many" are opposed to each other?
(3) Whether God is one?
(4) Whether He is in the highest degree one? _______________________
FIRST ARTICLE [I, Q. 11, Art. 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."