ntially?

(4) Whether it belongs to the Father alone to be unbegotten?
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FIRST ARTICLE [I, Q. 33, Art. 1]

Whether It Belongs to the Father to Be the Principle?

Objection 1: It would seem that the Father cannot be called the
principle of the Son, or of the Holy Ghost. For principle and cause
are the same, according to the Philosopher (Metaph. iv). But we do not
say that the Father is the cause of the Son. Therefore we must not say
that He is the principle of the Son.

Obj. 2: Further, a principle is so called in relation to the thing
principled. So if the Father is the principle of the Son, it follows
that the Son is a person principled, and is therefore created; which
appears false.

Obj. 3: Further, the word principle is taken from priority. But in
God there is no "before" and "after," as Athanasius says. Therefore
in speaking of God we ought not to used the term principle.

_On the contrary,_ Augustine says (De Trin. iv, 20), "The Father is
the Principle of the whole Deity."

_I answer that,_ The word "principle" signifies only that whence
another proceeds: since anything whence something proceeds in any way
we call a principle; and conversely. As the Father then is the one
whence another proceeds, it follows that the Father is a principle.

Reply Obj. 1: The Greeks use the words "cause" and "principle"
indifferently, when speaking of God; whereas the Latin Doctors do not
use the word "cause," but only "principle." The reason is because
"principle" is a wider term than "cause"; as "cause" is more common
than "element." For the first term of a thing, as also the first
part, is called the principle, but not the cause. Now the wider a
term is, the more suitable it is to use as regards God (Q. 13, A.
11), because the more special terms are, the more they determine the
mode adapted to the creature. Hence this term "cause" seems to mean
diversity of substance, and dependence of one from another; which is
not implied in the word "principle." For in all kinds of causes there
is always to be found between the cause and the effect a distance of
perfection or of power: whereas we use the term "principle" even in
things which have no such difference, but have only a certain order
to each other; as when we say that a point is the principle of a
line; or also when we say that the first part of a line is the
principle of a line.

Reply Obj. 2: It is the custom with the Greeks to say that the Son