Whether the power of begetting signifies a relation, and not the essence?
Objection 1: It would seem that the power of begetting, or of spirating, signifies the relation and not the essence. For power signifies a principle, as appears from its definition: for active power is the principle of action, as we find in Metaph. v, text 17. But in God principle in regard to Person is said notionally. Therefore, in God, power does not signify essence but relation.
Objection 2: Further, in God, the power to act [posse] and 'to act' are not distinct. But in God, begetting signifies relation. Therefore, the same applies to the power of begetting.
Objection 3: Further, terms signifying the essence in God, are common to the three persons. But the power of begetting is not common to the three persons, but proper to the Father. Therefore it does not signify the essence.
On the contrary, As God has the power to beget the Son, so also He wills to beget Him. But the will to beget signifies the essence. Therefore, also, the power to beget.
I answer that, Some have said that the power to beget signifies relation in God. But this is not possible. For in every agent, that is properly called power, by which the agent acts. Now, everything that produces something by its action, produces something like itself, as to the form by which it acts; just as man begotten is like his begetter in his human nature, in virtue of which the father has the power to beget a man. In every begetter, therefore, that is the power of begetting in which the begotten is like the begetter.
Now the Son of God is like the Father, who begets Him, in the divine nature. Wherefore the divine nature in the Father is in Him the power of begetting. And so Hilary says (De Trin. v): "The birth of God cannot but contain that nature from which it proceeded; for He cannot subsist other than God, Who subsists from no other source than God."
We must therefore conclude that the power of begetting signifies principally the divine essence as the Master says (Sent. i, D, vii), and not the relation only. Nor does it signify the essence as identified with the relation, so as to signify both equally. For although paternity is signified as the form of the Father, nevertheless it is a personal property, being in respect to the person of the Father, what the individual form is to the individual creature. Now the individual form in things created constitutes the person begetting, but is not that by which the begetter begets, otherwise Socrates would beget Socrates. So neither can paternity be understood as that by which the Father begets, but as constituting the person of the Father, otherwise the Father would beget the Father. But that by which the Father begets is the divine nature, in which the Son is like to Him. And in this sense Damascene says (De Fide Orth. i, 18) that generation is the "work of nature," not of nature generating, but of nature, as being that by which the generator generates. And therefore the power of begetting signifies the divine nature directly, but the relation indirectly.
Reply to Objection 1: Power does not signify the relation itself of a principle, for thus it would be in the genus of relation; but it signifies that which is a principle; not, indeed, in the sense in which we call the agent a principle, but in the sense of being that by which the agent acts. Now the agent is distinct from that which it makes, and the generator from that which it generates: but that by which the generator generates is common to generated and generator, and so much more perfectly, as the generation is more perfect. Since, therefore, the divine generation is most perfect, that by which the Begetter begets, is common to Begotten and Begetter by a community of identity, and not only of species, as in things created. Therefore, from the fact that we say that the divine essence "is the principle by which the Begetter begets," it does not follow that the divine essence is distinct (from the Begotten): which would follow if we were to say that the divine essence begets.
Reply to Objection 2: As in God, the power of begetting is the same as the act of begetting, so the divine essence is the same in reality as the act of begetting or paternity; although there is a distinction of reason.
Reply to Objection 3: When I speak of the "power of begetting," power is signified directly, generation indirectly: just as if I were to say, the "essence of the Father." Wherefore in respect of the essence, which is signified, the power of begetting is common to the three persons: but in respect of the notion that is connoted, it is proper to the person of the Father.
Whether several persons can be the term of one notional act?
Objection 1: It would seem that a notional act can be directed to several Persons, so that there may be several Persons begotten or spirated in God. For whoever has the power of begetting can beget. But the Son has the power of begetting. Therefore He can beget. But He cannot beget Himself: therefore He can beget another son. Therefore there can be several Sons in God.
Objection 2: Further, Augustine says (Contra Maxim. iii, 12): "The Son did not beget a Creator: not that He could not, but that it behoved Him not."
Objection 3: Further, God the Father has greater power to beget than has a created father. But a man can beget several sons. Therefore God can also: the more so that the power of the Father is not diminished after begetting the Son.
On the contrary, In God "that which is possible," and "that which is" do not differ. If, therefore, in God it were possible for there to be several Sons, there would be several Sons. And thus there would be more than three Persons in God; which is heretical.
I answer that, As Athanasius says, in God there is only "one Father, one Son, one Holy Ghost." For this four reasons may be given.
The first reason is in regard to the relations by which alone are the Persons distinct. For since the divine Persons are the relations themselves as subsistent, there would not be several Fathers, or several Sons in God, unless there were more than one paternity, or more than one filiation. And this, indeed, would not be possible except owing to a material distinction: since forms of one species are not multiplied except in respect of matter, which is not in God. Wherefore there can be but one subsistent filiation in God: just as there could be but one subsistent whiteness.
The second reason is taken from the manner of the processions. For God understands and wills all things by one simple act. Wherefore there can be but one person proceeding after the manner of word, which person is the Son; and but one person proceeding after the manner of love, which person is the Holy Ghost.
The third reason is taken from the manner in which the persons proceed. For the persons proceed naturally, as we have said ( Article [2]), and nature is determined to one.
The fourth reason is taken from the perfection of the divine persons. For this reason is the Son perfect, that the entire divine filiation is contained in Him, and that there is but one Son. The argument is similar in regard to the other persons.
Reply to Objection 1: We can grant, without distinction, that the Son has the same power as the Father; but we cannot grant that the Son has the power "generandi" [of begetting] thus taking "generandi" as the gerund of the active verb, so that the sense would be that the Son has the "power to beget." Just as, although Father and Son have the same being, it does not follow that the Son is the Father, by reason of the notional term added. But if the word "generandi" [of being begotten] is taken as the gerundive of the passive verb, the power "generandi" is in the Son---that is, the power of being begotten. The same is to be said if it be taken as the gerundive of an impersonal verb, so that the sense be "the power of generation"---that is, a power by which it is generated by some person.
Reply to Objection 2:
