Thomas Aquinas, Summa Theologiae

Objection 1: It would seem not right to say that the three persons are of one essence. For Hilary says (De Synod.) that the Father, Son and Holy Ghost "are indeed three by substance, but one in harmony." But the substance of God is His essence. Therefore the three persons are not of one essence.

Objection 2: Further, nothing is to be affirmed of God except what can be confirmed by the authority of Holy Writ, as appears from Dionysius (Div. Nom. i). Now Holy Writ never says that the Father, Son and Holy Ghost are of one essence. Therefore this should not be asserted.

Objection 3: Further, the divine nature is the same as the divine essence. It suffices therefore to say that the three persons are of one nature.

Objection 4: Further, it is not usual to say that the person is of the essence; but rather that the essence is of the person. Therefore it does not seem fitting to say that the three persons are of one essence.

Objection 5: Further, Augustine says (De Trin. vii, 6) that we do not say that the three persons are "from one essence ," lest we should seem to indicate a distinction between the essence and the persons in God. But prepositions which imply transition, denote the oblique case. Therefore it is equally wrong to say that the three persons are "of one essence ."

Objection 6: Further, nothing should be said of God which can be occasion of error. Now, to say that the three persons are of one essence or substance, furnishes occasion of error. For, as Hilary says (De Synod.): "One substance predicated of the Father and the Son signifies either one subsistent, with two denominations; or one substance divided into two imperfect substances; or a third prior substance taken and assumed by the other two." Therefore it must not be said that the three persons are of one substance.

On the contrary, Augustine says (Contra Maxim. iii) that the word {homoousion}, which the Council of Nicaea adopted against the Arians, means that the three persons are of one essence.

I answer that, As above explained (Question 13, Articles 1,2), divine things are named by our intellect, not as they really are in themselves, for in that way it knows them not; but in a way that belongs to things created. And as in the objects of the senses, whence the intellect derives its knowledge, the nature of the species is made individual by the matter, and thus the nature is as the form, and the individual is the "suppositum" of the form; so also in God the essence is taken as the form of the three persons, according to our mode of signification. Now in creatures we say that every form belongs to that whereof it is the form; as the health and beauty of a man belongs to the man. But we do not say of that which has a form, that it belongs to the form, unless some adjective qualifies the form; as when we say: "That woman is of a handsome figure," or: "This man is of perfect virtue." In like manner, as in God the persons are multiplied, and the essence is not multiplied, we speak of one essence of the three persons, and three persons of the one essence, provided that these genitives be understood as designating the form.

Reply to Objection 1: Substance is here taken for the "hypostasis," and not for the essence.

Reply to Objection 2: Although we may not find it declared in Holy Writ in so many words that the three persons are of one essence, nevertheless we find it so stated as regards the meaning; for instance, "I and the Father are one (Jn. 10:30)," and "I am in the Father, and the Father in Me (Jn. 10:38)"; and there are many other texts of the same import.

Reply to Objection 3: Because "nature" designates the principle of action while "essence" comes from being , things may be said to be of one nature which agree in some action, as all things which give heat; but only those things can be said to be of "one essence" which have one being. So the divine unity is better described by saying that the three persons are "of one essence," than by saying they are "of one nature."

Reply to Objection 4: Form, in the absolute sense, is wont to be designated as belonging to that of which it is the form, as we say "the virtue of Peter." On the other hand, the thing having form is not wont to be designated as belonging to the form except when we wish to qualify or designate the form. In which case two genitives are required, one signifying the form, and the other signifying the determination of the form, as, for instance, when we say, "Peter is of great virtue ," or else one genitive must have the force of two, as, for instance, "he is a man of blood"---that is, he is a man who sheds much blood . So, because the divine essence signifies a form as regards the person, it may properly be said that the essence is of the person; but we cannot say the converse, unless we add some term to designate the essence; as, for instance, the Father is a person of the "divine essence"; or, the three persons are "of one essence."

Reply to Objection 5: The preposition "from" or "out of" does not designate the habitude of a formal cause, but rather the habitude of an efficient or material cause; which causes are in all cases distinguished from those things of which they are the causes. For nothing can be its own matter, nor its own active principle. Yet a thing may be its own form, as appears in all immaterial things. So, when we say, "three persons of one essence," taking essence as having the habitude of form, we do not mean that essence is different from person, which we should mean if we said, "three persons from the same essence."

Reply to Objection 6: As Hilary says (De Synod.): "It would be prejudicial to holy things, if we had to do away with them, just because some do not think them holy. So if some misunderstand {homoousion}, what is that to me, if I understand it rightly? . . . The oneness of nature does not result from division, or from union or from community of possession, but from one nature being proper to both Father and Son."

Articulus 2

Argumentum 1

Ad secundum sic proceditur. Videtur quod non sit dicendum tres personas esse unius essentiae.

Dicit enim Hilarius, in libro de synod., quod pater et filius et spiritus sanctus sunt quidem per substantiam tria, per consonantiam vero unum.

Sed substantia dei est eius essentia.

Ergo tres personae non sunt unius essentiae.

Argumentum 2

Praeterea, non est affirmandum aliquid de divinis, quod auctoritate Scripturae sacrae non est expressum, ut patet per dionysium, I cap. De div. Nom..

Sed nunquam in Scriptura sacra exprimitur quod pater et filius et spiritus sanctus sunt unius essentiae. Ergo hoc non est asserendum.

Argumentum 3

Praeterea, natura divina est idem quod essentia. Sufficeret ergo dicere quod tres personae sunt unius naturae.

Argumentum 4

Praeterea, non consuevit dici quod persona sit essentiae, sed magis quod essentia sit personae. Ergo neque convenienter videtur dici quod tres personae sunt unius essentiae.

Argumentum 5

Praeterea, Augustinus dicit quod non dicimus tres personas esse ex una essentia, ne intelligatur in divinis aliud esse essentia et persona.

Sed sicut praepositiones sunt transitivae, ita et obliqui. Ergo, pari ratione, non est dicendum quod tres personae sunt unius essentiae.

Argumentum 6

Praeterea, id quod potest esse erroris occasio, non est in divinis dicendum. Sed cum dicuntur tres personae unius essentiae vel substantiae datur erroris occasio.

Quia, ut Hilarius dicit, in libro de synod., una substantia patris et filii praedicata, aut unum qui duas nuncupationes habeat, subsistentem significat; aut divisam unam substantiam duas imperfectas fecisse substantias; aut tertiam priorem substantiam, quae a duobus et usurpata sit et assumpta.

Non est ergo dicendum tres personas esse unius substantiae.

Sed Contra

Sed contra est quod Augustinus dicit, in libro II contra maximinum, quod hoc nomen homousion, quod in Concilio nicaeno adversus Arianos firmatum est, idem significat quod tres personas esse unius essentiae.

Corpus

Respondeo dicendum quod, sicut supra dictum est, intellectus noster res divinas nominat, non secundum modum earum, quia sic eas cognoscere non potest; sed secundum modum in rebus creatis inventum. Et quia in rebus sensibilibus, a quibus intellectus noster scientiam capit, natura alicuius speciei per materiam individuatur; et sic natura se habet ut forma, individuum autem ut suppositum formae, propter hoc etiam in divinis, quantum ad modum significandi, essentia significatur ut forma trium personarum. Dicimus autem in rebus creatis formam quamcumque esse eius cuius est forma; sicut sanitatem vel pulchritudinem hominis alicuius. Rem autem habentem formam non dicimus esse formae, nisi cum adiectione alicuius adiectivi, quod designat illam formam, ut cum dicimus, ista mulier est egregiae formae, iste homo est perfectae virtutis. Et similiter, quia in divinis, multiplicatis personis, non multiplicatur essentia, dicimus unam essentiam esse trium personarum; et tres personas unius essentiae, ut intelligantur isti genitivi construi in designatione formae.

Ad 1

Ad primum ergo dicendum quod substantia sumitur pro hypostasi; et non pro essentia.

Ad 2

Ad secundum dicendum quod, licet tres personas esse unius essentiae non inveniatur in sacra Scriptura per haec verba, invenitur tamen quantum ad hunc sensum, sicut ibi, ego et pater unum sumus; et, ego in patre, et pater in me est.

Et per multa alia haberi potest idem.

Ad 3

Ad tertium dicendum quod, quia natura designat principium actus, essentia vero ab essendo dicitur, possunt dici aliqua unius naturae, quae conveniunt in aliquo actu, sicut omnia calefacientia, sed unius essentiae dici non possunt, nisi quorum est unum esse. Et ideo magis exprimitur unitas divina per hoc quod dicitur quod tres personae sunt unius essentiae, quam si diceretur quod sunt unius naturae.

Ad 4

Ad quartum dicendum quod forma, absolute accepta, consuevit significari ut eius cuius est forma, ut virtus Petri. E converso autem, res habens formam aliquam non consuevit significari ut eius, nisi cum volumus determinare sive designare formam.

Et tunc requiruntur duo genitivi, quorum unus significet formam, et alius determinationem formae, ut si dicatur, Petrus est magnae virtutis, vel etiam requiritur unus genitivus habens vim duorum genitivorum, ut cum dicitur, vir sanguinum est iste, idest effusor multi sanguinis. Quia igitur essentia divina significatur ut forma respectu personae, convenienter essentia personae dicitur. Non autem e converso, nisi aliquid addatur ad designationem essentiae; ut si dicatur quod pater est persona divinae essentiae, vel quod tres personae sunt unius essentiae.

Ad 5

Ad quintum dicendum quod haec praepositio ex vel de non designat habitudinem causae formalis, sed magis habitudinem causae efficientis vel materialis. Quae quidem causae in omnibus distinguuntur ab his quorum sunt causae, nihil enim est sua materia, neque aliquid est suum principium activum. Aliquid tamen est sua forma, ut patet in omnibus rebus immaterialibus.

Et ideo per hoc quod dicimus tres personas unius essentiae, significando essentiam in habitudine formae, non ostenditur aliud esse essentia quam persona, quod ostenderetur, si diceremus tres personas ex eadem essentia.

Ad 6

Ad sextum dicendum quod, sicut Hilarius dicit, in libro de synod., male sanctis rebus praeiudicatur, si, quia non sanctae a quibusdam habentur, esse non debeant. Sic, si male intelligitur homousion, quid ad me bene intelligentem? sit ergo una substantia ex naturae genitae proprietate, non sit autem ex portione, aut ex unione, aut ex communione.