1 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.
1 Ad primum sic proceditur. Videtur quod pater non possit dici principium filii vel spiritus sancti. Principium enim et causa idem sunt, secundum philosophum. Sed non dicimus patrem esse causam filii. Ergo non debet dici quod sit eius principium.
2 Objection 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.
2 Praeterea, principium dicitur respectu principiati. Si igitur pater est principium filii, sequitur filium esse principiatum, et per consequens esse creatum. Quod videtur esse erroneum.
3 Objection 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.
3 Praeterea, nomen principii a prioritate sumitur. Sed in divinis non est prius et posterius, ut Athanasius dicit. Ergo in divinis non debemus uti nomine principii.
4 On the contrary, Augustine says De Trin. iv, 20), The Father is the Principle of the whole Deity.
4 Sed contra est quod dicit Augustinus, in IV de Trin., pater est principium totius deitatis.
5 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.
5 Respondeo dicendum quod hoc nomen principium nihil aliud significat quam id a quo aliquid procedit, omne enim a quo aliquid procedit quocumque modo, dicimus esse principium; et e converso. Cum ergo pater sit a quo procedit alius, sequitur quod pater est principium.
6 Reply to Objection 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 Question 13, Article 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.
6 Ad primum ergo dicendum quod Graeci utuntur in divinis indifferenter nomine causae, sicut et nomine principii, sed Latini doctores non utuntur nomine causae, sed solum nomine principii. Cuius ratio est, quia principium communius est quam causa, sicut causa communius quam elementum, primus enim terminus, vel etiam prima pars rei dicitur principium, sed non causa. Quanto autem aliquod nomen est communius, tanto convenientius assumitur in divinis, ut supra dictum est, quia nomina, quanto magis specialia sunt, tanto magis determinant modum convenientem creaturae. Unde hoc nomen causa videtur importare diversitatem substantiae, et dependentiam alicuius ab altero; quam non importat nomen principii. In omnibus enim causae generibus, semper invenitur distantia inter causam et id cuius est causa, secundum aliquam perfectionem aut virtutem. Sed nomine principii utimur etiam in his quae nullam huiusmodi differentiam habent, sed solum secundum quendam ordinem, sicut cum dicimus punctum esse principium lineae, vel etiam cum dicimus primam partem lineae esse principium lineae.
7 Reply to Objection 2: It is the custom with the Greeks to say that the Son and the Holy Ghost are principled. This is not, however, the custom with our Doctors; because, although we attribute to the Father something of authority by reason of His being the principle, still we do not attribute any kind of subjection or inferiority to the Son, or to the Holy Ghost, to avoid any occasion of error. In this way, Hilary says De Trin. ix): By authority of the Giver, the Father is the greater; nevertheless the Son is not less to Whom oneness of nature is give.
7 Ad secundum dicendum quod apud Graecos invenitur de filio vel spiritu sancto dici quod principientur. Sed hoc non est in usu doctorum nostrorum. Quia licet attribuamus patri aliquid auctoritatis ratione principii, nihil tamen ad subiectionem vel minorationem quocumque modo pertinens, attribuimus filio vel spiritui sancto, ut vitetur omnis erroris occasio. Secundum quem modum Hilarius dicit, IX de Trin., donantis auctoritate pater maior est; sed minor non est filius, cui unum esse donatur.
8 Reply to Objection 3: Although this word principle, as regards its derivation, seems to be taken from priority, still it does not signify priority, but origin. For what a term signifies, and the reason why it was imposed, are not the same thing, as stated above Question 13, Article 8).
8 Ad tertium dicendum quod, licet hoc nomen principium, quantum ad id a quo imponitur ad significandum, videatur a prioritate sumptum; non tamen significat prioritatem, sed originem. Non enim idem est quod significat nomen, et a quo nomen imponitur, ut supra dictum est.