Leo, the bishop, to Paschasinus, bishop of Lilybaeum.
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, test anything might have chanced to escape your care, I have despatched for your attentive perusal and study our letter1 , 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 flesh2 , since in the unity of person the Godhead and the manhood came together both in the conception and in the childbearing of the Virgin.
A like blasphemy, therefore, is to be abhorred in Eutyches, as was once condemned and overthrown by the Fathers in former heretics: and their example ought to have benefited this foolish fellow, in putting him on his guard against that which he could not grasp by his own sense, lest he should render void the peerless mystery of our salvation by denying the reality of human flesh in our Lord Jesus Christ. For, if there is not in Him true and perfect human nature, there is no taking of us upon Him, and the whole of our belief and teaching according to his heresy is emptiness and lying. But because the Truth does not lie and the Godhead is not possible, there abides in God the Word both substances in one Person, and the Church confesses her Saviour in such a way as to acknowledge Him both impossible in Godhead and possible in flesh, as says the Apostle, "although He was crucified through (our) weakness, yet He lives by the power of God3 ."
And in order that you may be the fuller instructed in all things, beloved, I have sent you certain quotations from our holy Fathers, that you may clearly gather what they felt and what they preached to the churches about the mystery of the Lord's Incarnation, which quotations our deputies produced at Constantinople also together with our epistle. And you must understand that the whole church of Constantinople, with all the monasteries and many bishops, have given their assent to it, and by their subscription have anathematized Nestorius and Eutyches with their dogmas. You must also understand that I have recently received the bishop of Constantinople's letter, which states that the bishop of Antioch has sent instructions to all the bishops throughout his provinces, and gained their assent to my epistle, and their condemnation of Nestorius and Eutyches in like manner.
This also we think necessary to enjoin upon your care that you should diligently inquire in those quarters where you are sure of information concerning that point in the reckoning of Easter, which we have found in the table4 of Theophilus, and which greatly exercises us, and that you should discuss with those who are learned in such calculations, as to the date, when the day of the Lord's resurrection should be held four years hence. For, whereas the next Easter is to be held by God's goodness on March 23rd, the year after on April 12th, the year after that on April 4th, Theophilus of holy memory has fixed April 24th to be observed in 455, which we find to be quite contrary to the rule of the Church; but in our Easter cycles5 as you know very well, Easter that year is set down to be kept on April 17th. And therefore, that all our doubts may be removed, we beg you carefully to discuss this point with the best authorities, that for the future we may avoid this kind of mistake. Dated June 24th in the consulship of the illustrious Adelfius (451).