I. He sends a copy of the Tome and still further explains the heterodoxy of Eutyches.
Although I doubt not all the sources of scandal are fully known to you, brother, which have arisen in the churches of the East about the Incarnation of our Lord Jesus Christ, yet, lest anything might have chanced to escape your care, I have dispatched for your attentive perusal and study our letter, which deals with this matter in the fullest way, which we sent to Flavian of holy memory, and which the universal Church has accepted; in order that, understanding how completely this whole blasphemous error has with God's aid been destroyed, you yourself also in your love towards God may show the same spirit, and know that they are utterly to be abhorred, who, following the blasphemy and madness of Eutyches, have dared to say there are not two natures, i.e. perfect Godhead and perfect manhood, in our Lord, the only-begotten Son of God, who took upon Himself to restore mankind; and think they can deceive our wariness by saying they believe the one nature of the Word to be Incarnate, whereas the Word of God in the Godhead of the Father, and of Himself, and of the Holy Spirit has indeed one nature; but when He took on Him the reality of our flesh, our nature also was united to His unchangeable substance: for even Incarnation could not be spoken of, unless the Word took on Him the flesh. And this taking on of flesh forms so complete a union, that not only in the blessed Virgin's child-bearing, but also in her conception, no division must be imagined between the Godhead and the life-endowed flesh, since in the unity of person the Godhead and the manhood came together both in the conception and in the childbearing of the Virgin.
Source: Letters (New Advent)