The rest of our discussion on Gregory Nazianzen will be devoted to what is the true core of his theology and mysticism, the idea of theosis, deification of the human person. This idea is a cantus firmus of the entire corpus of his discourses, from the First, which was pronounced at the threshold of his career as a preacher, to the Forty-fifth, which was written in his old age. This theme also runs through Gregory’s theological poetry.

            The terminology of deification which is employed by Eastern Fathers is borrowed from the Platonic tradition, while the doctrine itself has biblical roots. The idea of people as ‘gods’,[1] the notion of image and likeness of God in the human person,[2] the themes of our adoption by God,[3] our participation in the divine nature[4] and divine immortality[5] - all these notions form the basis of patristic teaching on deification.

            We find the idea of the deification of the human person the incarnate Word of God as early as in Irenaeus. According to him, the Word ‘became what we are in order to make us what He is’.[6] ‘The Word (became) man’, says Irenaeus, ‘and the Son of God (became) son of man so that man... might become a son of God’.[7] In other words, through the Incarnation of the Word, the human person becomes by adoption what the Son of God is by nature. This theme was developed by Clement and Origen. In the fourth century it found particular attention on the part of Nicene theologians in their polemic with Arianism. St Athanasius made the formula of Irenaeus even more concise: ‘God became man in order that we may become gods’.[8]

            However, it was precisely Gregory Nazianzen who made the idea of deification the foundation-stone of his theology, and it is after him that this theme would become a core of the development of the theological and mystical tradition in the Christian East. As D.Winslow rightly points out, ‘no Christian theologian prior to Gregory employed the term theosis (or the idea contained in the term) with as much consistence and frequency as did he; both terminologically and conceptually Gregory went far beyond his predecessors in his sustained application to theosis’.[9] Already in his first public sermon, the themes of the image of God, assimilation to Christ, adoption by God and deification in Christ become fundamental: 

...Let us recognize our dignity; let us honour our Archetype; let us know the power of the mystery,[10] and for what Christ died. Let us become like Christ, since Christ became like us. Let us become gods for His sake, since He for ours became man. He assumed the worse that He might give us the better; He became poor that we through His poverty might be rich; He took upon Himself the form of a servant that we might receive back our liberty; He came down that we might be exalted; He was tempted that we might conquer; He was dishonoured that He might glorify us; He died that He might save us; He ascended that He might draw to Himself us, who were lying low in the fall of sin. Let us give all, offer all, to Him Who gave Himself a ransom and a reconciliation for us. But one can give nothing like oneself, understanding the mystery, and becoming for His sake all that He became for ours.[11] 

            The goal of the Incarnation, says Gregory in his second public sermon, was ‘to make man god and partaker of heavenly bliss’.[12] By His sufferings Christ deified the human person, having mingled human image with heavenly one.[13] The leaven of deification mad human flesh ‘a new mixture’, and the intellect upon receiving this leaven ‘was mingled with God and deified through Divinity’.[14]

            Formulae of Irenaeus and Athanasius appear in Gregory’s writings in various modifications: 

Being God, You became man and was mingled with mortals: You were God from the beginning, and You became man later in order to make me god, since You became man.[15]

Christ... made me god through the image of a mortal (which He accepted upon Himself).[16]

The Word of the Father was God, but became man, as we are, so that, having mingled with the mortals, He might unite God with is.[17]

...As man, He is interceding for my salvation, until He makes me divine by the power of His incarnate manhood.[18]

Since man did not become god, God Himself became man... in order to reconstruct what was given through what is assumed.[19] 

            In his Theological Discourses Gregory adds a significant qualification to the formula of Athanasius: God became man ‘in order that I might be made god to the same extent that He was made man’.[20] Thus a direct link is established not only between the Incarnation of God and deification of man, but also between the extent to what God became man and man became god. Gregory adds this qualification in order to oppose the teaching of Apollinarius:[21] if God did not become an entire man, there is no possibility for a man to become entirely god. In one of his poems directed against Apollinarius, Gregory goes even further and places the Incarnation of God in direct dependence on the deification of man: ‘He became man to the same extent that He makes me god’.[22] Recognition of the fullness of the human nature in Christ presupposes the belief in deification of the entire human person, including his intellect, soul and body; and vice versa, the idea of deification presupposes faith in Christ as a human person with intellect, soul and body.

            The idea of participation of the body in deification is one of the main points of difference between Christian concept of deification and ins Platonic counterpart, the idea of ‘becoming god’, which we find in Plotinus.[23] In the latter’s philosophical system, the matter always remains evil and opposed to everything divine.[24] Gregory, on the contrary, asserts that in the person of Christ the flesh is deified by the Spirit: the incarnate God is ‘one from two opposites, flesh and spirit, of which the latter deifies and the former is deified’.[25] In the same manner the body of every person who attained to deification in Christ becomes transfigured and deified: 

By narrow and difficult way, through narrow gates,

which are not passable for many, with a solemn escort,

Christ leads to God me, a god made of dust,

who was not born god, but was made immortal from mortal.

Together with the great image of God[26] He draws also my body, which is my assistant,

in the same manner as a magnet-stone attracts black iron.[27]