Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that there are more than three persons in God. For the plurality of persons in God arises from the plurality of the relative properties as stated above (Article 1). But there are four relations in God as stated above (Question 28, Article 4), paternity, filiation, common spiration, and procession. Therefore there are four persons in God.

Objection 2: The nature of God does not differ from His will more than from His intellect. But in God, one person proceeds from the will, as love; and another proceeds from His nature, as Son. Therefore another proceeds from His intellect, as Word, besides the one Who proceeds from His nature, as Son; thus again it follows that there are not only three persons in God.

Objection 3: Further, the more perfect a creature is, the more interior operations it has; as a man has understanding and will beyond other animals. But God infinitely excels every creature. Therefore in God not only is there a person proceeding from the will, and another from the intellect, but also in an infinite number of ways. Therefore there are an infinite number of persons in God.

Objection 4: Further, it is from the infinite goodness of the Father that He communicates Himself infinitely in the production of a divine person. But also in the Holy Ghost is infinite goodness. Therefore the Holy Ghost produces a divine person; and that person another; and so to infinity.

Objection 5: Further, everything within a determinate number is measured, for number is a measure. But the divine persons are immense, as we say in the Creed of Athanasius: "The Father is immense, the Son is immense, the Holy Ghost is immense." Therefore the persons are not contained within the number three.

On the contrary, It is said: "There are three who bear witness in heaven, the father, the Word, and the Holy Ghost" (1 Jn. 5:7). To those who ask, "Three what?" we answer, with Augustine (De Trin. vii, 4), "Three persons." Therefore there are but three persons in God.

I answer that, As was explained above, there can be only three persons in God. For it was shown above that the several persons are the several subsisting relations really distinct from each other. But a real distinction between the divine relations can come only from relative opposition. Therefore two opposite relations must needs refer to two persons: and if any relations are not opposite they must needs belong to the same person. Since then paternity and filiation are opposite relations, they belong necessarily to two persons. Therefore the subsisting paternity is the person of the Father; and the subsisting filiation is the person of the Son. The other two relations are not opposed to each other; therefore these two cannot belong to one person: hence either one of them must belong to both of the aforesaid persons; or one must belong to one person, and the other to the other. Now, procession cannot belong to the Father and the Son, or to either of them; for thus it would follows that the procession of the intellect, which in God is generation, wherefrom paternity and filiation are derived, would issue from the procession of love, whence spiration and procession are derived, if the person generating and the person generated proceeded from the person spirating; and this is against what was laid down above (Question 27, Articles 3,4). We must frequently admit that spiration belongs to the person of the Father, and to the person of the Son, forasmuch as it has no relative opposition either to paternity or to filiation; and consequently that procession belongs to the other person who is called the person of the Holy Ghost, who proceeds by way of love, as above explained. Therefore only three persons exist in God, the Father, the Son, and the Holy Ghost.

Reply to Objection 1: Although there are four relations in God, one of them, spiration, is not separated from the person of the Father and of the Son, but belongs to both; thus, although it is a relation, it is not called a property, because it does not belong to only one person; nor is it a personal relation---i.e. constituting a person. The three relations---paternity, filiation, and procession---are called personal properties, constituting as it were the persons; for paternity is the person of the Father, filiation is the person of the Son, procession is the person of the Holy Ghost proceeding.

Reply to Objection 2: That which proceeds by way of intelligence, as word, proceeds according to similitude, as also that which proceeds by way of nature; thus, as above explained (Question 27, Article 3), the procession of the divine Word is the very same as generation by way of nature. But love, as such, does not proceed as the similitude of that whence it proceeds; although in God love is co-essential as being divine; and therefore the procession of love is not called generation in God.

Reply to Objection 3: As man is more perfect than other animals, he has more intrinsic operations than other animals, because his perfection is something composite. Hence the angels, who are more perfect and more simple, have fewer intrinsic operations than man, for they have no imagination, or feeling, or the like. In God there exists only one real operation---that is, His essence. How there are in Him two processions was above explained (Question 27, Articles 1,4).

Reply to Objection 4: This argument would prove if the Holy Ghost possessed another goodness apart from the goodness of the Father; for then if the Father produced a divine person by His goodness, the Holy Ghost also would do so. But the Father and the Holy Ghost have one and the same goodness. Nor is there any distinction between them except by the personal relations. So goodness belongs to the Holy Ghost, as derived from another; and it belongs to the Father, as the principle of its communication to another. The opposition of relation does not allow the relation of the Holy Ghost to be joined with the relation of principle of another divine person; because He Himself proceeds from the other persons who are in God.

Reply to Objection 5: A determinate number, if taken as a simple number, existing in the mind only, is measured by one. But when we speak of a number of things as applied to the persons in God, the notion of measure has no place, because the magnitude of the three persons is the same (Question 42, Articles 1,4), and the same is not measured by the same.

Articulus 2

Argumentum 1

Ad secundum sic proceditur. Videtur quod in deo sint plures personae quam tres. Pluralitas enim personarum in divinis est secundum pluralitatem proprietatum relativarum, ut dictum est.

Sed quatuor sunt relationes in divinis, ut supra dictum est, scilicet paternitas, filiatio, communis spiratio et processio. Ergo quatuor personae sunt in divinis.

Argumentum 2

Praeterea, non plus differt natura a voluntate in deo, quam natura ab intellectu. Sed in divinis est alia persona quae procedit per modum voluntatis, ut amor; et alia quae procedit per modum naturae, ut filius. Ergo est etiam alia quae procedit per modum intellectus, ut verbum; et alia quae procedit per modum naturae, ut filius. Et sic iterum sequitur quod non sunt tantum tres personae in divinis.

Argumentum 3

Praeterea, in rebus creatis quod excellentius est, plures habet operationes intrinsecas, sicut homo supra alia animalia habet intelligere et velle. Sed deus in infinitum excedit omnem creaturam. Ergo non solum est ibi persona procedens per modum voluntatis et per modum intellectus, sed infinitis aliis modis. Ergo sunt infinitae personae in divinis.

Argumentum 4

Praeterea, ex infinita bonitate patris est, quod infinite seipsum communicet, producendo personam divinam. Sed etiam in spiritu sancto est infinita bonitas. Ergo spiritus sanctus producit divinam personam, et illa aliam, et sic in infinitum.

Argumentum 5

Praeterea, omne quod continetur sub determinato numero, est mensuratum, numerus enim mensura quaedam est. Sed personae divinae sunt immensae, ut patet per Athanasium, immensus pater, immensus filius, immensus spiritus sanctus.

Non ergo sub numero ternario continentur.

Sed Contra

Sed contra est quod dicitur I Ioan. Ult., tres sunt qui testimonium dant in caelo, pater, verbum et spiritus sanctus.

Quaerentibus autem, quid tres? respondetur, tres personae, ut Augustinus dicit, in VII de Trin..

Sunt igitur tres personae tantum in divinis.

Corpus

Respondeo dicendum quod, secundum praemissa, necesse est ponere tantum tres personas in divinis.

Ostensum est enim quod plures personae sunt plures relationes subsistentes, ab invicem realiter distinctae. Realis autem distinctio inter relationes divinas non est nisi in ratione oppositionis relativae. Ergo oportet duas relationes oppositas ad duas personas pertinere, si quae autem relationes oppositae non sunt, ad eandem personam necesse est eas pertinere.

Paternitas ergo et filiatio, cum sint oppositae relationes, ad duas personas ex necessitate pertinent. Paternitas igitur subsistens est persona patris, et filiatio subsistens est persona filii. Aliae autem duae relationes ad neutram harum oppositionem habent, sed sibi invicem opponuntur. Impossibile est igitur quod ambae uni personae conveniant. Oportet ergo quod vel una earum conveniat utrique dictarum personarum, aut quod una uni, et alia alii. Non autem potest esse quod processio conveniat patri et filio, vel alteri eorum, quia sic sequeretur quod processio intellectus, quae est generatio in divinis, secundum quam accipitur paternitas et filiatio, prodiret ex processione amoris, secundum quam accipitur spiratio et processio, si persona generans et genita procederent a spirante, quod est contra praemissa.

Relinquitur ergo quod spiratio conveniat et personae patris et personae filii, utpote nullam habens oppositionem relativam nec ad paternitatem nec ad filiationem. Et per consequens oportet quod conveniat processio alteri personae, quae dicitur persona spiritus sancti, quae per modum amoris procedit, ut supra habitum est.

Relinquitur ergo tantum tres personas esse in divinis, scilicet patrem et filium et spiritum sanctum.

Ad 1

Ad primum ergo dicendum quod, licet sint quatuor relationes in divinis, tamen una earum, scilicet spiratio, non separatur a persona patris et filii, sed convenit utrique. Et sic, licet sit relatio, non tamen dicitur proprietas, quia non convenit uni tantum personae, neque est relatio personalis, idest constituens personam. Sed hae tres relationes, paternitas, filiatio et processio, dicuntur proprietates personales, quasi personas constituentes, nam paternitas est persona patris, filiatio persona filii, processio persona spiritus sancti procedentis.

Ad 2

Ad secundum dicendum quod id quod procedit per modum intellectus, ut verbum, procedit secundum rationem similitudinis, sicut etiam id quod procedit per modum naturae, et ideo supra dictum est quod processio verbi divini est ipsa generatio per modum naturae. Amor autem, inquantum huiusmodi, non procedit ut similitudo illius a quo procedit (licet in divinis amor sit coessentialis inquantum est divinus), et ideo processio amoris non dicitur generatio in divinis.

Ad 3

Ad tertium dicendum quod homo, cum sit perfectior aliis animalibus, habet plures operationes intrinsecas quam alia animalia, quia eius perfectio est per modum compositionis. Unde in Angelis, qui sunt perfectiores et simpliciores, sunt pauciores operationes intrinsecae quam in homine, quia in eis non est imaginari, sentire, et huiusmodi. Sed in deo, secundum rem, non est nisi una operatio, quae est sua essentia.

Sed quomodo sunt duae processiones, supra ostensum est.

Ad 4

Ad quartum dicendum quod ratio illa procederet, si spiritus sanctus haberet aliam numero bonitatem a bonitate patris, oporteret enim quod, sicut pater per suam bonitatem producit personam divinam, ita et spiritus sanctus. Sed una et eadem bonitas patris est et spiritus sancti. Neque etiam est distinctio nisi per relationes personarum. Unde bonitas convenit spiritui sancto quasi habita ab alio, patri autem, sicut a quo communicatur alteri. Oppositio autem relationis non permittit ut cum relatione spiritus sancti sit relatio principii respectu divinae personae, quia ipse procedit ab aliis personis quae in divinis esse possunt.

Ad 5

Ad quintum dicendum quod numerus determinatus, si accipiatur numerus simplex, qui est tantum in acceptione intellectus, per unum mensuratur. Si vero accipiatur numerus rerum in divinis personis, sic non competit ibi ratio mensurati, quia eadem est magnitudo trium personarum, ut infra patebit; idem autem non mensuratur per idem.