d so the Trinity was not believed explicitly.

Obj. 3: Further, that which we are bound to believe explicitly of God
is the object of heavenly happiness. Now the object of heavenly
happiness is the sovereign good, which can be understood to be in
God, without any distinction of Persons. Therefore it was not
necessary to believe explicitly in the Trinity.

_On the contrary,_ In the Old Testament the Trinity of Persons is
expressed in many ways; thus at the very outset of Genesis it is
written in manifestation of the Trinity: "Let us make man to Our image
and likeness" (Gen. 1:26). Therefore from the very beginning it was
necessary for salvation to believe in the Trinity.

_I answer that,_ It is impossible to believe explicitly in the
mystery of Christ, without faith in the Trinity, since the mystery of
Christ includes that the Son of God took flesh; that He renewed the
world through the grace of the Holy Ghost; and again, that He was
conceived by the Holy Ghost. Wherefore just as, before Christ, the
mystery of Christ was believed explicitly by the learned, but
implicitly and under a veil, so to speak, by the simple, so too was
it with the mystery of the Trinity. And consequently, when once grace
had been revealed, all were bound to explicit faith in the mystery of
the Trinity: and all who are born again in Christ, have this bestowed
on them by the invocation of the Trinity, according to Matt. 28:19:
"Going therefore teach ye all nations, baptizing them in the name of
the Father, and of the Son and of the Holy Ghost."

Reply Obj. 1: Explicit faith in those two things was necessary at all
times and for all people: but it was not sufficient at all times and
for all people.

Reply Obj. 2: Before Christ's coming, faith in the Trinity lay hidden
in the faith of the learned, but through Christ and the apostles it
was shown to the world.

Reply Obj. 3: God's sovereign goodness as we understand it now
through its effects, can be understood without the Trinity of
Persons: but as understood in itself, and as seen by the Blessed, it
cannot be understood without the Trinity of Persons. Moreover the
mission of the Divine Persons brings us to heavenly happiness.
_______________________

NINTH ARTICLE [II-II, Q. 2, Art. 9]

Whether to Believe Is Meritorious?

Objection 1: It would seem that to believe is not meritorious. For
the principle of all merit is charity, as stated above (I-II, Q. 114,
A. 4). Now faith, like nature,