stand for the Father, its mode of signification
being different. This objection would hold good as regards things
which are predicated of another as the universal of a particular.

Reply Obj. 5: The difference between substantive and adjectival names
consist in this, that the former carry their subject with them,
whereas the latter do not, but add the thing signified to the
substantive. Whence logicians are wont to say that the substantive is
considered in the light of _suppositum,_ whereas the adjective
indicates something added to the _suppositum._ Therefore substantive
personal terms can be predicated of the essence, because they are
really the same; nor does it follow that a personal property makes a
distinct essence; but it belongs to the _suppositum_ implied in the
substantive. But notional and personal adjectives cannot be
predicated of the essence unless we add some substantive. We cannot
say that the "essence is begetting"; yet we can say that the "essence
is a thing begetting," or that it is "God begetting," if "thing" and
God stand for person, but not if they stand for essence. Consequently
there exists no contradiction in saying that "essence is a thing
begetting," and "a thing not begetting"; because in the first case
"thing" stands for person, and in the second it stands for the
essence.

Reply Obj. 6: So far as Godhead is one in several _supposita,_ it
agrees in a certain degree with the form of a collective term. So
when we say, "the Father is the principle of the whole Godhead," the
term Godhead can be taken for all the persons together, inasmuch as
it is the principle in all the divine persons. Nor does it follow
that He is His own principle; as one of the people may be called the
ruler of the people without being ruler of himself. We may also say
that He is the principle of the whole Godhead; not as generating or
spirating it, but as communicating it by generation and spiration.
_______________________

SIXTH ARTICLE [I, Q. 39, Art. 6]

Whether the Persons Can Be Predicated of the Essential Terms?

Objection 1: It would seem that the persons cannot be predicated of
the concrete essential names; so that we can say for instance, "God is
three persons"; or "God is the Trinity." For it is false to say, "man
is every man," because it cannot be verified as regards any particular
subject. For neither Socrates, nor Plato, nor anyone else is every
man. In the same way this proposition, "God is the Trinit