Saint Cyril wrote three letters to Nestorius asking him to reconcile his teaching with the orthodox teachings of the fathers of the church, but Nestorius did not accept. The letters of Saint Cyril always began with the salutation: "To the most pious and most God-loving bishop Nestorius". His third and last letter to Nestorius was sent from "Cyril and the synod assembled in Alexandria from the diocese of Egypt".
On the other hand, concerning the man-God Christology, it is clear that this can be a great heresy. If someone is going to claim that the Antiochene Christology is based in that way, to say that the Logos assumed a man at the same moment when that man was formed in the womb of the Virgin Saint Mary, this would not mean that the Logos became incarnate or God manifested in flesh, but that man became God in Jesus Christ.
The Word of God did not assume a man with a human prosopon (person) but He became man by assuming perfect humanity and uniting it to Himself from the very moment of incarnation.
Generally speaking, the person is identified according to the nature which he possesses. God the Logos possesses the divine nature and as a man possesses the human nature. The person, being the owner and carrier of the nature, can be Himself divine and human at the same time. This can happen if He is the eternal Logos who became man in the fullness of time. The Logos was possessing the divine essence of the Fr. from eternity in His own prosopon (person).
The Logos was possessing the divine essence of the Fr. from eternity in His own prosopon (person).
In the incarnation the same prosopon of the Logos is possessing the human essence of our nature making this essence His very own, so that there was no need for a human prosopon to be added to the prosopon of the Logos. In His own prosopon the human nature was personalised and became a perfect man without sin- and at the same time He remained a perfect God as He was, with His natures united without mixture, without change, without confusion, and without separation.
Saint Cyril also was aiming to differentiate between dwelling and union. Thus he wrote in his third letter to Nestorius:
"Neither do we say that the Word of God dwelled, as in an ordinary man, in the one born of the Holy Virgin, in order that Christ might not be thought to be a man bearing God … But united according to nature (kata phusin) and not changed into flesh, the Word produced an indwelling such as the soul of man might be said to have in its own body".
There are mysteries about which we should not use our thoughts to go deeper than necessary, remembering what Saint Paul said, "I know a man in Christ who fourteen years ago, whether in the body I do not know, or whether out of the body I do not know, God knows" (2 Corinthians XII: 2).
Concerning the teaching of Nestorius it is very clear that he taught two persons united in one person in Jesus Christ and that is why he refused the term "Theotokos" to express the birth of the incarnate God from the Virgin Saint Mary. He considered the one born from her as merely a man in conjoining (conjunction) with the Logos the Son of God. Quotations are given as follows:
(1) "Two are the prosopa, the prosopon of he who has clothed and the prosopon of he who is clothed".
(2) "Therefore the image of God is the perfect expression of God to me. The image of God is understood in this sense, can be thought of as the divine prosopon. God dwells in Christ and perfectly reveals himself to men through him. Yet the two prosopa are really one image of God."
(3) "We must not forget that the two natures involve with him two distinct hypostases and two persons
(prosopons) united together by simple loan and exchange."
1. LH 193 (Bazaar of Heraclides) quoted by Bernard Dupay, OP, "The Christology of Nestorius", Syriac Dialogue, Pro Oriente, op. cit., p113.
2. Rowan Greer, "The Image of God and the Prosopic Union in Nestorius", Bazaar of Heraclides in Lux in Lumine, Essays to honour W. Norman Pittenger, edited by R.A. Morris Jr. New York 1966, p.50.
3. R. Nau, Le Livre d’Heraclide de Damas (=L.H.), Paris 1910; p. xxviii