Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that the Son of God assumed the whole human nature through the medium of its parts. For Augustine says (De Agone Christ. xviii) that "the invisible and unchangeable Truth assumed the soul through the medium of the spirit, and the body through the medium of the soul, and in this way the whole man." But the spirit, soul, and body are parts of the whole man. Therefore He assumed all, through the medium of the parts.

Objection 2: Further, the Son of God assumed flesh through the medium of the soul because the soul is more like to God than the body. But the parts of human nature, since they are simpler than the body, would seem to be more like to God, Who is most simple, than the whole. Therefore He assumed the whole through the medium of the parts.

Objection 3: Further, the whole results from the union of parts. But the union is taken to be the term of the assumption, and the parts are presupposed to the assumption. Therefore He assumed the whole by the parts.

On the contrary, Damascene says (De Fide Orth. iii, 16): "In our Lord Jesus Christ we do not behold parts of parts, but such as are immediately joined, i.e. the Godhead and the manhood." Now the humanity is a whole, which is composed of soul and body, as parts. Therefore the Son of God assumed the parts through the medium of the whole.

I answer that, When anything is said to be a medium in the assumption of the Incarnation, we do not signify order of time, because the assumption of the whole and the parts was simultaneous. For it has been shown (Articles 3,4) that the soul and body were mutually united at the same time in order to constitute the human nature of the Word. But it is order of nature that is signified. Hence by what is prior in nature, that is assumed which is posterior in nature. Now a thing is prior in nature in two ways: First on the part of the agent, secondly on the part of the matter; for these two causes precede the thing. On the part of the agent---that is simply first, which is first included in his intention; but that is relatively first, with which his operation begins---and this because the intention is prior to the operation. On the part of the matter---that is first which exists first in the transmutation of the matter. Now in the Incarnation the order depending on the agent must be particularly considered, because, as Augustine says (Ep. ad Volusianum cxxxvii), "in such things the whole reason of the deed is the power of the doer." But it is manifest that, according to the intention of the doer, what is complete is prior to what is incomplete, and, consequently, the whole to the parts. Hence it must be said that the Word of God assumed the parts of human nature, through the medium of the whole; for even as He assumed the body on account of its relation to the rational soul, so likewise He assumed a body and soul on account of their relation to human nature.

Reply to Objection 1: From these words nothing may be gathered, except that the Word, by assuming the parts of human nature, assumed the whole human nature. And thus the assumption of parts is prior in the order of the intellect, if we consider the operation, but not in order of time; whereas the assumption of the nature is prior if we consider the intention: and this is to be simply first, as was said above.

Reply to Objection 2: God is so simple that He is also most perfect; and hence the whole is more like to God than the parts, inasmuch as it is more perfect.

Reply to Objection 3: It is a personal union wherein the assumption is terminated, not a union of nature, which springs from a conjunction of parts.

Articulus 5

Argumentum 1

Ad quintum sic proceditur. Videtur quod filius dei assumpserit totam naturam humanam mediantibus partibus.

Dicit enim Augustinus, in libro de agone christiano, quod invisibilis et incommutabilis veritas per spiritum animam, per animam corpus, et sic totum hominem assumpsit.

Sed spiritus, anima et corpus sunt partes totius hominis.

Ergo totum hominem assumpsit mediantibus partibus.

Argumentum 2

Praeterea, ideo dei filius carnem assumpsit mediante anima, quia anima est deo similior quam corpus. Sed partes humanae naturae, cum sint simpliciores videntur esse similiores ei, qui est simplicissimus, quam totum. Ergo assumpsit totum mediantibus partibus.

Argumentum 3

Praeterea, totum resultat ex unione partium. Sed unio intelligitur ut terminus assumptionis, partes autem praeintelliguntur assumptioni. Ergo assumpsit totum per partes.

Sed Contra

Sed contra est quod Damascenus dicit, in III libro, in domino iesu christo non partes partium intuemur, sed quae proxime componuntur, idest deitatem et humanitatem.

Humanitas autem est quoddam totum, quod componitur ex anima et corpore sicut ex partibus. Ergo filius dei assumpsit partes mediante toto.

Corpus

Respondeo dicendum quod, cum dicitur aliquid medium in assumptione incarnationis, non designatur ordo temporis, quia simul facta est assumptio totius et omnium partium.

Ostensum est enim quod simul anima et corpus sunt ad invicem unita ad constituendam naturam humanam in verbo. Designatur autem ibi ordo naturae. Unde per id quod est prius natura, assumitur id quod est posterius. Est autem aliquid prius in natura dupliciter, uno modo ex parte agentis, alio modo ex parte materiae; hae enim duae causae praeexistunt rei. Ex parte quidem agentis, est simpliciter primum id quod primo cadit in eius intentione, sed secundum quid est primum illud a quo incipit eius operatio, et hoc ideo, quia intentio est prior operatione. Ex parte vero materiae, est prius illud quod prius existit in transmutatione materiae. In incarnatione autem oportet maxime attendere ordinem qui est ex parte agentis, quia, ut Augustinus dicit, in epistola ad volusianum, in talibus rebus tota ratio facti est potentia facientis.

Manifestum est autem quod secundum intentionem facientis prius est completum quam incompletum, et per consequens, totum quam partes. Et ideo dicendum est quod verbum dei assumpsit partes humanae naturae mediante toto. Sicut enim corpus assumpsit propter ordinem quem habet ad animam rationalem, ita assumpsit corpus et animam propter ordinem quem habent ad humanam naturam.

Ad 1

Ad primum ergo dicendum quod ex verbis illis nihil datur intelligi nisi quod verbum, assumendo partes humanae naturae, assumpsit totam humanam naturam.

Et sic assumptio partium prior est in via operationis intellectu, non tempore. Assumptio autem naturae est prior in via intentionis, quod est esse prius simpliciter, ut dictum est.

Ad 2

Ad secundum dicendum quod deus ita est simplex quod etiam est perfectissimus. Et ideo totum est magis simile deo quam partes, inquantum est perfectius.

Ad 3

Ad tertium dicendum quod unio personalis est ad quam terminatur assumptio, non autem unio naturae, quae resultat ex coniunctione partium.