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."
_______________________

SECOND ARTICLE [I, Q. 11, Art. 2]

Whether "One" and "Many" Are Opposed to Each Other?

Objection 1: It seems that "one" and "many" are not mutually opposed.
For no opposite thing is predicated of its opposite. But every
_multitude_ is in a certain way _one,_ as appears from the preceding
article. Therefore "one" is not opposed to "multitude."

Obj. 2: Further, no opposite thing is constituted by its
opposite. But _multitude_ is constituted by _one._ Therefore it is not
opposed to "multitude."

Obj. 3: Further, "one" is opposed to "one." But the idea of "few"
is opposed to "many." Therefore "one" is not opposed to "many."

Obj. 4: Further,