(CG 4/34). Of the Error of Theodore of Mopsuestia concerning the Union of ... (Book 4. God, in His Revelation) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

EUTYCHES, to save the unity of person in Christ against Nestorius, said that in Christ there was only one nature. He went on to explain how before the union there were two distinct natures, one divine and one human; but in the union they both met so as to form one. He said then that the person of Christ was of two natures, but did not subsist in two natures. The falsity of this statement is apparent on many counts.

1. In Christ Jesus there was a Body, and a natural Soul, and the Divinity. The Body of Christ, even after the union, was not the Divinity of the Word: for the Body of Christ, even after the union, was passible, visible to bodily eyes, and distinct in lineaments and limbs, all of which attributes are alien to the Divinity of the Word. In like manner the Soul of Christ after union was distinct from the Divinity of the Word, because the Soul of Christ, even after the union, was affected by the passions of sadness and grief and anger (Mark iii, 5: xiv, 34), which again can in no way be adapted to the Divinity of the Word. But soul and body make up human nature. Thus then, even after union, there was a human nature in Christ, other than the Divinity of the Word, which is the divine nature.

2. Being in the form of God, he took the form of a servant (Phil. ii, 6, 7). It cannot be said that the form of God and the form of a servant are the same, for nothing takes that which it already has. In Eutyches's view, Christ having already the form of God, could not have taken the form of a servant, the two being the same. Nor can it be said that the form of God in Christ was changed by the union, for so Christ after the union would not be God. Nor again can it be said that the form of the servant was mingled with the form of God, for mingled elements do not remain entire, but both are partially changed: hence it should not be said that He had taken the form of a servant, but something of that form. Thus the Apostle's words must mean that in Christ, even after union, there were two forms, therefore two natures.

3. If we suppose a blending of both natures, divine and human, neither would remain, but some third thing; and thus Christ would be neither God nor man. Eutyches then cannot be understood to mean that one nature was made out of the two. He can only mean that after union only one of the natures remained. Either then in Christ only the divine nature remained, and what seemed in Him human was merely phenomenal, as the Manicheans said; or the divine nature was changed into a human nature, as Apollinaris said: against both of whom we have argued above (Chapp. XXIX, XXXI).

5. When one nature is constituted of two permanent components, these components are either bodily parts, like the limbs of an animal, a case not in point here, or they are matter and form, like body and soul: but God is not matter, nor can He stand to any matter in the relation of form. Therefore in Christ, true God and true Man, there cannot be one nature only.

7. Where there is no agreement in nature, there is no specific likeness. If then the nature of Christ is a compound of divine and human, there will be no specific likeness between Him and us, contrary to the saying of the Apostle: He ought in all things to be made like to his brethren (Heb. ii, 17).

9. Even this saying of Eutyches seems inconsistent with the faith, that there were two natures in Christ before the union: for as human nature is made up of body and soul, it would follow that either the soul, or the body of Christ, or both, existed before the Incarnation, which is evidently false.