We now consider the persons singly; and first, the Person of the
Father, concerning Whom there are four points of inquiry:
(1) Whether the Father is the Principle?
(2) Whether the person of the Father is properly signified by this name "Father"?
(3) Whether "Father" in God is said personally before it is said essentially?
(4) Whether it belongs to the Father alone to be unbegotten? _______________________
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.