Re-reading Justinian’s Edict ‘On the Orthodox Faith’ in the translation by Richard Price,* I am struck by a passage that relates directly to the question of Nestorianism and monasticism. As you will recall, I have hypothesised that the reason a selection of ascetic writers oppose Nestorianism is because Nestorianism undermines the goal of ascetic and mystical practice, which is theosis.
The positive affirmation of how Chalcedonian/Neo-Chalcedonian or, indeed, Miaphysite, Christology contributes to theosis is found in this edict. I give a long-ish extract with the most pertinent part in bold:
For the Word was born from above from the Father ineffably, indescribably, incomprehensibly and eternally, and the same is born in time from below from the Virgin Mary, so that those once born from below may be born a second time from above, that is, from God. Therefore he has a mother only on earth, while we have a Father only in heaven. For taking the mortal father of mankind, Adam, he gave to mankind his own immortal Father, according to the saying, ‘He gave them power to become children of God.’ (Jn 1:12) Accordingly the Son of God tasted death in the flesh because of his fleshly father, so that the sons of man might receive a share in his life because of God their spiritual Father. So he is the Son of God by nature, while we are so by grace. And again according to the dispensation and for our sake he became a son of Adam, while we are sons of Adam by nature. For God is his Father by nature but ours by grace; and he became his God according to the dispensation because he [the Son] became man, while by nature he is God our master. And therefore the Word, who is the Son of the Father, was united to the flesh and became flesh, so that men united to the Spirit might become one Spirit. Therefore the true Son of God himself puts on us all so that we may all put on the one God. Even after becoming man he is one of the holy Trinity, the only-begotten Son of God, our Lord Jesus Christ, composite from both natures; that Christ is composite we profess, following the teaching of the holy fathers. (trans. Price, p. 133)
Justinian goes on to affirm the full unity of Christ as a single hypostasis. It is this union, the hypostatic union, as explained by Neo-Chalcedonian theology that makes theosis possible, whereas the division implied by what is called ‘Nestorianism’ makes theosis unattainable.
God became man so that man might become God, as the famous Athanasian saying goes. This is only possible if one and the same Christ is fully God and fully man without division.
A quick note, of course: All talk of ‘Nestorianism’ has nothing really to do with the Church of the East, given that Isaac the Syrian certainly affirms theosis.
*In vol. 1 of The Acts of the Council of Constantinople of 553; I’ve reviewed the translation by Kenneth P. Wesche in On the Person of Christ already.