hin the number three.

_On the contrary,_ It is said: "There are three who bear witness in
heaven, the Father, the Word, and the Holy Ghost" (1 John 5:7). To
those who ask, "Three what?" we answer, with Augustine (De Trin. vii,
4), "Three persons." Therefore there are but three persons in God.

_I answer that,_ As was explained above, there can be only three
persons in God. For it was shown above that the several persons are
the several subsisting relations really distinct from each other. But
a real distinction between the divine relations can come only from
relative opposition. Therefore two opposite relations must needs
refer to two persons: and if any relations are not opposite they must
needs belong to the same person. Since then paternity and filiation
are opposite relations, they belong necessarily to two persons.
Therefore the subsisting paternity is the person of the Father; and
the subsisting filiation is the person of the Son. The other two
relations are not opposed to each other; therefore these two cannot
belong to one person: hence either one of them must belong to both of
the aforesaid persons; or one must belong to one person, and the
other to the other. Now, procession cannot belong to the Father and
the Son, or to either of them; for thus it would follows that the
procession of the intellect, which in God is generation, wherefrom
paternity and filiation are derived, would issue from the procession
of love, whence spiration and procession are derived, if the person
generating and the person generated proceeded from the person
spirating; and this is against what was laid down above (Q. 27, AA.
3, 4). We must consequently admit that spiration belongs to the
person of the Father, and to the person of the Son, forasmuch as it
has no relative opposition either to paternity or to filiation; and
consequently that procession belongs to the other person who is
called the person of the Holy Ghost, who proceeds by way of love, as
above explained. Therefore only three persons exist in God, the
Father, the Son, and the Holy Ghost.

Reply Obj. 1: Although there are four relations in God, one of them,
spiration, is not separated from the person of the Father and of the
Son, but belongs to both; thus, although it is a relation, it is not
called a property, because it does not belong to only one person; nor
is it a personal relation--i.e. constituting a person. The three
relations--paternity, filiation, and processio