1 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.
1 Ad sextum sic proceditur. Videtur quod actus notionalis ad plures personas terminari possit, ita quod sint plures personae genitae vel spiratae in divinis. Cuicumque enim inest potentia generandi, potest generare. Sed filio inest potentia generandi. Ergo potest generare. Non autem seipsum. Ergo alium filium. Ergo possunt esse plures filii in divinis.
2 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.
2 Praeterea, Augustinus dicit, contra Maximinum, filius non genuit creatorem. Neque enim non potuit, sed non oportuit.
3 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.
3 Praeterea, Deus pater est potentior ad generandum quam pater creatus. Sed unus homo potest generare plures filios. Ergo et Deus, praecipue cum potentia patris, uno filio generato, non diminuatur.
4 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.
4 Sed contra est quod in divinis non differt esse et posse. Si igitur in divinis possent esse plures filii, essent plures filii. Et ita essent plures personae quam tres in divinis, quod est haereticum.
5 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.
5 Respondeo dicendum quod, sicut Athanasius dicit, in divinis est tantum unus pater, unus filius, unus spiritus sanctus. Cuius quidem ratio quadruplex assignari potest. Prima quidem ex parte relationum, quibus solum personae distinguuntur. Cum enim personae divinae sint ipsae relationes subsistentes, non possent esse plures patres vel plures filii in divinis, nisi essent plures paternitates et plures filiationes. Quod quidem esse non posset nisi secundum materialem rerum distinctionem, formae enim unius speciei non multiplicantur nisi secundum materiam, quae in divinis non est. Unde in divinis non potest esse nisi una tantum filiatio subsistens; sicut et albedo subsistens non posset esse nisi una. Secunda vero ex modo processionum. Quia Deus omnia intelligit et vult uno et simplici actu. Unde non potest esse nisi una persona procedens per modum verbi, quae est filius; et una tantum per modum amoris, quae est spiritus sanctus. Tertia ratio sumitur ex modo procedendi. Quia personae ipsae procedunt naturaliter, ut dictum est, natura autem determinatur ad unum. Quarta ex perfectione divinarum personarum. Ex hoc enim est perfectus filius, quod tota filiatio divina in eo continetur, et quod est tantum unus filius. Et similiter dicendum est de aliis personis.
6 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.
6 Ad primum ergo dicendum quod, quamvis simpliciter concedendum sit quod potentiam quam habet pater, habeat filius; non tamen concedendum est quod filius habeat potentiam generandi, si generandi sit gerundivum verbi activi, ut sit sensus quod filius habeat potentiam ad generandum. Sicut, licet idem esse sit patris et filii, non tamen convenit filio esse patrem, propter notionale adiunctum. Si tamen hoc quod dico generandi, sit gerundivum verbi passivi, potentia generandi est in filio, idest ut generetur. Et similiter si sit gerundivum verbi impersonalis, ut sit sensus, potentia generandi, idest qua ab aliqua persona generatur.
7 Reply to Objection 2: Augustine does not mean to say by those words that the Son could beget a Son: but that if He did not, it was not because He could not, as we shall see later on Question 42, Article 6, ad 3).
7 Ad secundum dicendum quod Augustinus in verbis illis non intendit dicere quod filius posset generare filium, sed quod hoc non est ex impotentia filii, quod non generet, ut infra patebit.
8 Reply to Objection 3: Divine perfection and the total absence of matter in God require that there cannot be several Sons in God, as we have explained. Wherefore that there are not several Sons is not due to any lack of begetting power in the Father.
8 Ad tertium dicendum quod immaterialitas et perfectio divina requirit ut non possint esse plures filii in divinis, sicut dictum est. Unde quod non sint plures filii, non est ex impotentia patris ad generandum.