Whether the Trinity of the Divine Persons Can Be Known by Natural
Reason?
Objection 1: It would seem that the trinity of the divine persons can
be known by natural reason. For philosophers came to the knowledge of
God not otherwise than by natural reason. Now we find that they said
many things about the trinity of persons, for Aristotle says (De Coelo
et Mundo i, 2): "Through this number"--namely, three--"we bring
ourselves to acknowledge the greatness of one God, surpassing all
things created." And Augustine says (Confess. vii, 9): "I have read in
their works, not in so many words, but enforced by many and various
reasons, that in the beginning was the Word, and the Word was with
God, and the Word was God," and so on; in which passage the
distinction of persons is laid down. We read, moreover, in a gloss on
Rom. 1 and Ex. 8 that the magicians of Pharaoh failed in the third
sign--that is, as regards knowledge of a third person--i.e. of the
Holy Ghost--and thus it is clear that they knew at least two
persons. Likewise Trismegistus says: "The monad begot a monad, and
reflected upon itself its own heat." By which words the generation of
the Son and procession of the Holy Ghost seem to be indicated.
Therefore knowledge of the divine persons can be obtained by natural
reason.
Obj. 2: Further, Richard St. Victor says (De Trin. i, 4): "I believe
without doubt that probable and even necessary arguments can be found
for any explanation of the truth." So even to prove the Trinity some
have brought forward a reason from the infinite goodness of God, who
communicates Himself infinitely in the procession of the divine
persons; while some are moved by the consideration that "no good
thing can be joyfully possessed without partnership." Augustine
proceeds (De Trin. x, 4; x, 11, 12) to prove the trinity of persons
by the procession of the word and of love in our own mind; and we
have followed him in this (Q. 27, AA. 1, 3). Therefore the trinity of
persons can be known by natural reason.
Obj. 3: Further, it seems to be superfluous to teach what cannot be
known by natural reason. But it ought not to be said that the divine
tradition of the Trinity is superfluous. Therefore the trinity of
persons can be known by natural reason.
_On the contrary,_ Hilary says (De Trin. i), "Let no man think to
reach the sacred mystery of generation by his own mind." And Ambrose
says (De Fide ii, 5), "It is impossible to know the secret of
generation. The mind fails, the voice is silent." But the trinity of
the divine persons is distinguished by origin of generation and
procession (Q. 30, A. 2). Since, therefore, man cannot know, and with
his understanding grasp that for which no necessary reason can be
given, it follows that the trinity of persons cannot be known by
reason.
_I answer that,_ It is impossible to attain to the knowledge of the
Trinity by natural reason. For, as above explained (Q. 12, AA. 4,
12), man cannot obtain the knowledge of God by natural reason except
from creatures. Now creatures lead us to the knowledge of God, as
effects do to their cause. Accordingly, by natural reason we can know
of God that only which of necessity belongs to Him as the principle
of things, and we have cited this fundamental principle in treating
of God as above (Q. 12, A. 12). Now, the creative power of God is
common to the whole Trinity; and hence it belongs to the unity of the
essence, and not to the distinction of the persons. Therefore, by
natural reason we can know what belongs to the unity of the essence,
but not what belongs to the distinction of the persons. Whoever,
then, tries to prove the trinity of persons by natural reason,
derogates from faith in two ways. Firstly, as regards the dignity of
faith itself, which consists in its being concerned with invisible
things, that exceed human reason; wherefore the Apostle says that
"faith is of things that appear not" (Heb. 11:1), and the same
Apostle says also, "We speak wisdom among the perfect, but not the
wisdom of this world, nor of the princes of this world; but we speak
the wisdom of God in a mystery which is hidden" (1 Cor. 2:6, 7).
Secondly, as regards the utility of drawing others to the faith. For
when anyone in the endeavor to prove the faith brings forward reasons
which are not cogent, he falls under the ridicule of the unbelievers:
since they suppose that we stand upon such reasons, and that we
believe on such grounds.
Therefore, we must not attempt to prove what is of faith, except by
authority alone, to those who receive the authority; while as regards
others it suffices to prove that what faith teaches is not impossible.
Hence it is said by Dionysius (Div. Nom. ii): "Whoever wholly resists
the word, is far off from our philosophy; whereas if he regards the
truth of the word"--i.e. "the sacred word, we too follow this rule."
Reply Obj. 1: The philosophers did not know the mystery of the
trinity of the divine persons by its proper attributes, such as
paternity, filiation, and procession, according to the Apostle's
words, "We speak the wisdom of God which none of the princes of the
world"--i.e. the philosophers--"knew" (1 Cor. 2:6). Nevertheless,
they knew some of the essential attributes appropriated to the
persons, as power to the Father, wisdom to the Son, goodness to the
Holy Ghost; as will later on appear. So, when Aristotle said, "By this
number," etc., we must not take it as if he affirmed a threefold
number in God, but that he wished to say that the ancients used the
threefold number in their sacrifices and prayers on account of some
perfection residing in the number three. In the Platonic books also
we find, "In the beginning was the word," not as meaning the Person
begotten in God, but as meaning the ideal type whereby God made all
things, and which is appropriated to the Son. And although they knew
these were appropriated to the three persons, yet they are said to
have failed in the third sign--that is, in the knowledge of the third
person, because they deviated from the goodness appropriated to the
Holy Ghost, in that knowing God "they did not glorify Him as God"
(Rom. 1); or, because the Platonists asserted the existence of one
Primal Being whom they also declared to be the father of the universe,
they consequently maintained the existence of another substance
beneath him, which they called "mind" or the "paternal intellect,"
containing the idea of all things, as Macrobius relates (Som. Scip.
iv). They did not, however, assert the existence of a third separate
substance which might correspond to the Holy Ghost. So also we do not
assert that the Father and the Son differ in substance, which was the
error of Origen and Arius, who in this followed the Platonists. When
Trismegistus says, "Monad begot monad," etc., this does not refer to
the generation of the Son, or to the procession of the Holy Ghost, but
to the production of the world. For one God produced one world by
reason of His love for Himself.
Reply Obj. 2: Reason may be employed in two ways to establish a
point: firstly, for the purpose of furnishing sufficient proof of
some principle, as in natural science, where sufficient proof can be
brought to show that the movement of the heavens is always of uniform
velocity. Reason is employed in another way, not as furnishing a
sufficient proof of a principle, but as confirming an already
established principle, by showing the congruity of its results, as in
astrology the theory of eccentrics and epicycles is considered as
established, because thereby the sensible appearances of the heavenly
movements can be explained; not, however, as if this proof were
sufficient, forasmuch as some other theory might explain them. In the
first way, we can prove that God is one; and the like. In the second
way, reasons avail to prove the Trinity; as, when assumed to be true,
such reasons confirm it. We must not, however, think that the trinity
of persons is adequately proved by such reasons. This becomes evident
when we consider each point; for the infinite goodness of God is
manifested also in creation, because to produce from nothing is an
act of infinite power. For if God communicates Himself by His
infinite goodness, it is not necessary that an infinite effect should
proceed from God: but that according to its own mode and capacity it
should receive the divine goodness. Likewise, when it is said that
joyous possession of good requires partnership, this holds in the
case of one not having perfect goodness: hence it needs to share some
other's good, in order to have the goodness of complete happiness.
Nor is the image in our mind an adequate proof in the case of God,
forasmuch as the intellect is not in God and ourselves univocally.
Hence, Augustine says (Tract. xxvii. in Joan.) that by faith we
arrive at knowledge, and not conversely.
Reply Obj. 3: There are two reasons why the knowledge of the divine
persons was necessary for us. It was necessary for the right idea of
creation. The fact of saying that God made all things by His Word
excludes the error of those who say that God produced things by
necessity. When we say that in Him there is a procession of love, we
show that God produced creatures not because He needed them, nor
because of any other extrinsic reason, but on account of the love of
His own goodness. So Moses, when he had said, "In the beginning God
created heaven and earth," subjoined, "God said, Let there be light,"
to manifest the divine Word; and then said, "God saw the light that
it was good," to show proof of the divine love. The same is also
found in the other works of creation. In another way, and chiefly,
that we may think rightly concerning the salvation of the human race,
accomplished by the Incarnate Son, and by the gift of the Holy Ghost.
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