Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that the person proceeding is not co-eternal with His principle, as the Son with the Father. For Arius gives twelve modes of generation. The first mode is like the issue of a line from a point; wherein is wanting equality of simplicity. The second is like the emission of rays from the sun; wherein is absent equality of nature. The third is like the mark or impression made by a seal; wherein is wanting consubstantiality and executive power. The fourth is the infusion of a good will from God; wherein also consubstantiality is wanting. The fifth is the emanation of an accident from its subject; but the accident has no subsistence. The sixth is the abstraction of a species from matter, as sense receives the species from the sensible object; wherein is wanting equality of spiritual simplicity. The seventh is the exciting of the will by knowledge, which excitation is merely temporal. The eighth is transformation, as an image is made of brass; which transformation is material. The ninth is motion from a mover; and here again we have effect and cause. The tenth is the taking of species from genera; but this mode has no place in God, for the Father is not predicated of the Son as the genus of a species. The eleventh is the realization of an idea , as an external coffer arises from the one in the mind. The twelfth is birth, as a man is begotten of his father; which implies priority and posteriority of time. Thus it is clear that equality of nature or of time is absent in every mode whereby one thing is from another. So if the Son is from the Father, we must say that He is less than the Father, or later than the Father, or both.

Objection 2: Further, everything that comes from another has a principle. But nothing eternal has a principle. Therefore the Son is not eternal; nor is the Holy Ghost.

Objection 3: Further, everything which is corrupted ceases to be. Hence everything generated begins to be; for the end of generation is existence. But the Son is generated by the Father. Therefore He begins to exist, and is not co-eternal with the Father.

Objection 4: Further, if the Son be begotten by the Father, either He is always being begotten, or there is some moment in which He is begotten. If He is always being begotten, since, during the process of generation, a thing must be imperfect, as appears in successive things, which are always in process of becoming, as time and motion, it follows that the Son must be always imperfect, which cannot be admitted. Thus there is a moment to be assigned for the begetting of the Son, and before that moment the Son did not exist.

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 (Question 41, Article 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 (Question 41, Article 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 to Objection 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 to Objection 2: Eternity excludes the principle of duration, but not the principle of origin.

Reply to Objection 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 (Question 27, Article 2). Hence the Son is ever being begotten, and the Father is always begetting.

Reply to Objection 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 (Question 10, Article 2 ad 1, Article 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 and Augustine 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.

Articulus 2

Argumentum 1

Ad secundum sic proceditur. Videtur quod persona procedens non sit coaeterna suo principio, ut filius patri.

Arius enim duodecim modos generationis assignat.

Primus modus est iuxta fluxum lineae a puncto, ubi deest aequalitas simplicitatis. Secundus modus est iuxta emissionem radiorum a sole, ubi deest aequalitas naturae. Tertius modus est iuxta characterem, seu impressionem a sigillo, ubi deest consubstantialitas et potentiae efficientia. Quartus modus est iuxta immissionem bonae voluntatis a deo, ubi etiam deest consubstantialitas. Quintus modus est iuxta exitum accidentis a substantia, sed accidenti deest subsistentia. Sextus modus est iuxta abstractionem speciei a materia, sicut sensus accipit speciem a re sensibili, ubi deest aequalitas simplicitatis spiritualis. Septimus modus est iuxta excitationem voluntatis a cogitatione, quae quidem excitatio temporalis est. Octavus modus est iuxta transfigurationem, ut ex aere fit imago, quae materialis est. Nonus modus est motus a movente, et hic etiam ponitur effectus et causa. Decimus modus est iuxta eductionem specierum a genere, qui non competit in divinis, quia pater non praedicatur de filio sicut genus de specie. Undecimus modus est iuxta ideationem, ut arca exterior ab ea quae est in mente.

Duodecimus modus est iuxta nascentiam, ut homo est a patre, ubi est prius et posterius secundum tempus.

Patet ergo quod in omni modo quo aliquid est ex altero, aut deest aequalitas naturae, aut aequalitas durationis. Si igitur filius est a patre, oportet dicere vel eum esse minorem patre, aut posteriorem, aut utrumque.

Argumentum 2

Praeterea, omne quod est ex altero, habet principium. Sed nullum aeternum habet principium. Ergo filius non est aeternus, neque spiritus sanctus.

Argumentum 3

Praeterea, omne quod corrumpitur, desinit esse. Ergo omne quod generatur, incipit esse, ad hoc enim generatur, ut sit. Sed filius est genitus a patre.

Ergo incipit esse, et non est coaeternus patri.

Argumentum 4

Praeterea, si filius genitus est a patre, aut semper generatur, aut est dare aliquod instans suae generationis. Si semper generatur; dum autem aliquid est in generari, est imperfectum, sicut patet in successivis, quae sunt semper in fieri, ut tempus et motus, sequitur quod filius semper sit imperfectus; quod est inconveniens. Est ergo dare aliquod instans generationis filii. Ante illud ergo instans filius non erat.

Sed Contra

Sed contra est quod Athanasius dicit, quod totae tres personae coaeternae sibi sunt.

Corpus

Respondeo dicendum quod necesse est dicere filium esse coaeternum patri. Ad cuius evidentiam, considerandum est quod aliquid ex principio existens posterius esse suo principio, potest contingere ex duobus, uno modo, ex parte agentis; alio modo, ex parte actionis. Ex parte agentis quidem, aliter in agentibus voluntariis, aliter in agentibus naturalibus. In agentibus quidem voluntariis, propter electionem temporis, sicut enim in agentis voluntarii potestate est eligere formam quam effectui conferat, ut supra dictum est, ita in eius potestate est eligere tempus in quo effectum producat. In agentibus autem naturalibus hoc contingit, quia agens aliquod non a principio habet perfectionem virtutis naturaliter ad agendum, sed ei advenit post aliquod tempus; sicut homo non a principio generare potest.

Ex parte autem actionis, impeditur ne id quod est a principio simul sit cum suo principio, propter hoc quod actio est successiva.

Unde, dato quod aliquod agens tali actione agere inciperet statim cum est, non statim eodem instanti esset effectus, sed in instanti ad quod terminatur actio.

Manifestum est autem secundum praemissa, quod pater non generat filium voluntate, sed natura. Et iterum, quod natura patris ab aeterno perfecta fuit. Et iterum, quod actio qua pater producit filium, non est successiva, quia sic filius dei successive generaretur, et esset eius generatio materialis et cum motu, quod est impossibile. Relinquitur ergo quod filius fuit, quandocumque fuit pater. Et sic filius est coaeternus patri, et similiter spiritus sanctus utrique.

Ad 1

Ad primum ergo dicendum quod, sicut Augustinus dicit, in libro de verbis domini, nullus modus processionis alicuius creaturae perfecte repraesentat divinam generationem, unde oportet ex multis modis colligere similitudinem, ut quod deest ex uno, aliqualiter suppleatur ex altero.

Et propter hoc dicitur in synodo ephesina, coexistere semper coaeternum patri filium, splendor tibi denuntiet, impassibilitatem nativitatis ostendat verbum; consubstantialitatem filii nomen insinuet.

Inter omnia tamen expressius repraesentat processio verbi ab intellectu, quod quidem non est posterius eo a quo procedit; nisi sit talis intellectus qui exeat de potentia in actum, quod in deo dici non potest.

Ad 2

Ad secundum dicendum quod aeternitas excludit principium durationis, sed non principium originis.

Ad 3

Ad tertium dicendum quod omnis corruptio est mutatio quaedam, et ideo omne quod corrumpitur, incipit non esse, et desinit esse.

Sed generatio divina non est transmutatio, ut dictum est supra.

Unde filius semper generatur, et pater semper generat.

Ad 4

Ad quartum dicendum quod in tempore aliud est quod est indivisibile, scilicet instans; et aliud est quod est durans, scilicet tempus. Sed in aeternitate ipsum nunc indivisibile est semper stans, ut supra dictum est.

Generatio vero filii non est in nunc temporis, aut in tempore, sed in aeternitate.

Et ideo, ad significandum praesentialitatem et permanentiam aeternitatis, potest dici quod semper nascitur, ut Origenes dixit. Sed, ut Gregorius et Augustinus dicunt, melius est quod dicatur semper natus, ut ly semper designet permanentiam aeternitatis, et ly natus perfectionem geniti.

Sic ergo filius nec imperfectus est, neque erat quando non erat, ut Arius dixit.