Q: Whether the Person Proceeding Is Co-eternal with His Principle, As the Son with the Father?

A: On the contrary,
Athanasius declares that "all the three persons are co-eternal with each other."

I answer that,
We must say that the Son is co-eternal with the Father. In proof of which we must consider that for a thing which proceeds from a principle to be posterior to its principle may be due to two reasons: one on the part of the agent, and the other on the part of the action. On the part of the agent this happens differently as regards free agents and natural agents. In free agents, on account of the choice of time; for as a free agent can choose the form it gives to the effect, as stated above (Q. 41, A. 2), so it can choose the time in which to produce its effect. In natural agents, however, the same happens from the agent not having its perfection of natural power from the very first, but obtaining it after a certain time; as, for instance, a man is not able to generate from the very first. Considered on the part of action, anything derived from a principle cannot exist simultaneously with its principle when the action is successive. So, given that an agent, as soon as it exists, begins to act thus, the effect would not exist in the same instant, but in the instant of the action's termination. Now it is manifest, according to what has been said (Q. 41, A. 2), that the Father does not beget the Son by will, but by nature; and also that the Father's nature was perfect from eternity; and again that the action whereby the Father produces the Son is not successive, because thus the Son would be successively generated, and this generation would be material, and accompanied with movement; which is quite impossible. Therefore we conclude that the Son existed whensoever the Father existed and thus the Son is co-eternal with the Father, and likewise the Holy Ghost is co-eternal with both.

Reply Obj. 1: As Augustine says (De Verbis Domini, Serm. 38), no mode of the procession of any creature perfectly represents the divine generation. Hence we need to gather a likeness of it from many of these modes, so that what is wanting in one may be somewhat supplied from another; and thus it is declared in the council of Ephesus: "Let Splendor tell thee that the co-eternal Son existed always with the Father; let the Word announce the impassibility of His birth; let the name Son insinuate His consubstantiality." Yet, above them all the procession of the word from the intellect represents it more exactly; the intellectual word not being posterior to its source except in an intellect passing from potentiality to act; and this cannot be said of God.

Reply Obj. 2: Eternity excludes the principle of duration, but not the principle of origin.

Reply Obj. 3: Every corruption is a change; and so all that corrupts begins not to exist and ceases to be. The divine generation, however, is not changed, as stated above (Q. 27, A. 2). Hence the Son is ever being begotten, and the Father is always begetting.

Reply Obj. 4: In time there is something indivisible--namely, the instant; and there is something else which endures--namely, time. But in eternity the indivisible "now" stands ever still, as we have said above (Q. 10, A. 2, ad 1; A. 4, ad 2). But the generation of the Son is not in the "now" of time, or in time, but in eternity. And so to express the presentiality and permanence of eternity, we can say that "He is ever being born," as Origen said (Hom. in Joan. i). But as Gregory [*Moral. xxix, 21] and Augustine [*Super Ps. 2:7] said, it is better to say "ever born," so that "ever" may denote the permanence of eternity, and "born" the perfection of the only Begotten. Thus, therefore, neither is the Son imperfect, nor "was there a time when He was not," as Arius said.