re implied in a collective term, plurality
of the _supposita,_ and a unity of some kind of order. For "people"
is a multitude of men comprehended under a certain order. In the
first sense, this word "trinity" is like other collective words; but
in the second sense it differs from them, because in the divine
Trinity not only is there unity of order, but also with this there is
unity of essence.

Reply Obj. 3: "Trinity" is taken in an absolute sense; for it
signifies the threefold number of persons. "Triplicity" signifies a
proportion of inequality; for it is a species of unequal proportion,
according to Boethius (Arithm. i, 23). Therefore in God there is not
triplicity, but Trinity.

Reply Obj. 4: In the divine Trinity is to be understood both number
and the persons numbered. So when we say, "Trinity in Unity," we do
not place number in the unity of the essence, as if we meant three
times one; but we place the Persons numbered in the unity of nature;
as the _supposita_ of a nature are said to exist in that nature. On
the other hand, we say "Unity in Trinity"; meaning that the nature is
in its _supposita._

Reply Obj. 5: When we say, "Trinity is trine," by reason of the
number implied, we signify the multiplication of that number by
itself; since the word trine imports a distinction in the _supposita_
of which it is spoken. Therefore it cannot be said that the Trinity
is trine; otherwise it follows that, if the Trinity be trine, there
would be three _supposita_ of the Trinity; as when we say, "God is
trine," it follows that there are three _supposita_ of the Godhead.
_______________________

SECOND ARTICLE [I, Q. 31, Art. 2]

Whether the Son Is Other Than the Father?

Objection 1: It would seem that the Son is not other than the Father.
For "other" is a relative term implying diversity of substance. If,
then, the Son is other than the Father, He must be different from the
Father; which is contrary to what Augustine says (De Trin. vii), that
when we speak of three persons, "we do not mean to imply diversity."

Obj. 2: Further, whosoever are other from one another, differ in
some way from one another. Therefore, if the Son is other than the
Father, it follows that He differs from the Father; which is against
what Ambrose says (De Fide i), that "the Father and the Son are one
in Godhead; nor is there any difference in substance between them,
nor any diversity."

Obj. 3: Further, the term alien is taken from _alius