if "one" is opposed to "multitude," it is
opposed as the undivided is to the divided; and is thus opposed to it
as privation is to habit. But this appears to be incongruous; because
it would follow that "one" comes after "multitude," and is defined by
it; whereas, on the contrary, "multitude" is defined by "one." Hence
there would be a vicious circle in the definition; which is
inadmissible. Therefore "one" and "many" are not opposed.

_On the contrary,_ Things which are opposed in idea, are themselves
opposed to each other. But the idea of "one" consists in
indivisibility; and the idea of "multitude" contains division.
Therefore "one" and "many" are opposed to each other.

_I answer that,_ "One" is opposed to "many," but in various ways. The
_one_ which is the principle of number is opposed to _multitude_ which
is number, as the measure is to the thing measured. For "one" implies
the idea of a primary measure; and number is _multitude_ measured by
_one,_ as is clear from _Metaph._ x. But the _one_ which is convertible
with _being_ is opposed to _multitude_ by way of privation; as the
undivided is to the thing divided.

Reply Obj. 1: No privation entirely takes away the being of a thing,
inasmuch as privation means "negation in the subject," according to
the Philosopher (Categor. viii). Nevertheless every privation takes
away some being; and so in being, by reason of its universality, the
privation of being has its foundation in being; which is not the case
in privations of special forms, as of sight, or of whiteness and the
like. And what applies to being applies also to one and to good,
which are convertible with being, for the privation of good is
founded in some good; likewise the removal of unity is founded in
some one thing. Hence it happens that multitude is some one thing;
and evil is some good thing, and non-being is some kind of being.
Nevertheless, opposite is not predicated of opposite; forasmuch as
one is absolute, and the other is relative; for what is relative
being (as a potentiality) is non-being absolutely, i.e. actually; or
what is absolute being in the genus of substance is non-being
relatively as regards some accidental being. In the same way, what is
relatively good is absolutely bad, or vice versa; likewise what is
absolutely _one_ is relatively _many,_ and vice versa.

Reply Obj. 2: A _whole_ is twofold. In one sense it is homogeneous,
composed of like parts; in another sense it is heterogene