Another term used for deification or divinization is Christification. This is based on the idea that there is a Christological structure to the human being and the destiny of humanity is to be found in Christ. Theosis is the mystery of human nature’s perfection in Christ, not its alteration or destruction, because Theosis is the mystery of eternal life in communion with God in the divine Word (Christ). So in accord with God’s Divine Plan, humans were created to learn how to enter into a union with God through imitation of Jesus Christ and living in accord with God’s Spirit. We humans were created for this end.
The theological background to the prominence of the idea of deification in Eastern soteriology (doctrine of salvation through Jesus Christ) is the emphasis of the Eastern fathers on the incarnation and the role of the Holy Spirit who communicates the grace that deifies humans and makes them sharers of divine life. They believed that through the incarnation the mortal had been changed into immortal and the passable into impassible. The great Eastern teachers, Athanasius, both Gregorys and Cyril of Alexandria insisted that it was by the incarnation of the Word of God that humanity was anointed by the Holy Spirit. According to Cyril, Christ filled his whole body with the life-giving power of the Spirit…. It was not the flesh that gave like to the Spirit, but the power of the Spirit that gave life to the flesh.
With regard to Theosis, the two patristic texts most often cited are from Irenaeus and Athanasius. Irenaeus: The word of God, our Lord Jesus Christ… did through His transcendent Love, become what we are, that He might bring us to be even what He is Himself. Athanasius: He, indeed, assumed humanity that we might become God. Still another early text from Origen is a favored one: according to him, when we transcend the material realm the contemplation of God is brought to its proper fulfillment, which fulfillment is the spirit to be deified by that which it contemplates. Many other examples from the Eastern fathers could be added, for example, from Gregory of Nyssa who said, God united Himself to our nature in order that our nature might be made divine through union with God. Another Gregory, of Nazianzus, echoes this by saying that as God became incarnate, man became divinized, and that to the extent that Christ became a real man, so we become real gods. For Athanasius, the emphasis on deification comes also from his opposition to the Arian heresy, which was also a theory of deification, although in the judgment of the mainstream Christian theology a false one. Arianism considered Christ the first creature who was deified in a very special way, though still like us. Athanasius responded to that by saying that what in itself proves the full divinity of the Word is that we are deified through and in him.