Orthodox theology
http://orthodoxwiki.org/Theosis
Theosis ("deification," "divinization") is the process of a worshiper becoming free of hamartía ("missing the mark"), being united with God, beginning in this life and later consummated in bodily resurrection. For Orthodox Christians, Théōsis (see 2 Pet. 1:4) is salvation. Théōsis assumes that humans from the beginning are made to share in the Life or Nature of the all-Holy Trinity. Therefore, an infant or an adult worshiper is saved from the state of unholiness (hamartía — which is not to be confused with hamártēma “sin”) for participation in the Life (zōé, not simply bíos) of the Trinity — which is everlasting.
This is not to be confused with the heretical (apothéōsis) - "Deification in God’s Essence", which is imparticipable.
The statement by St. Athanasius of Alexandria, "The Son of God became man, that we might become god", [the second g is always lowercase since man can never become a God] indicates the concept beautifully. II Peter 1:4 says that we have become " . . . partakers of divine nature." Athanasius amplifies the meaning of this verse when he says theosis is "becoming by grace what God is by nature" (De Incarnatione, I). What would otherwise seem absurd, that fallen, sinful man may become holy as God is holy, has been made possible through Jesus Christ, who is God incarnate. Naturally, the crucial Christian assertion, that God is One, sets an absolute limit on the meaning of theosis - it is not possible for any created being to become, ontologically, God or even another god.
Through theoria, the knowledge of God in Jesus Christ, human beings come to know and experience what it means to be fully human (the created image of God); through their communion with Jesus Christ God shares Himself with the human race, in order to conform them to all that God is in knowledge, righteousness and holiness. Theosis also asserts the complete restoration of all people (and of the entire creation), in principle. This is built upon the understanding of the atonement put forward by Irenaeus of Lyons, called "recapitulation."
For many fathers, theosis goes beyond simply restoring people to their state before the Fall of Adam and Eve, teaching that because Christ united the human and divine natures in his person, it is now possible for someone to experience closer fellowship with God than Adam and Eve initially experienced in the Garden of Eden, and that people can become more like God than Adam and Eve were at that time. Some Orthodox theologians go so far as to say that Jesus would have become incarnate for this reason alone, even if Adam and Eve had never sinned.
All of humanity is fully restored to the full potential of humanity because the Son of God took to Himself a human nature to be born of a woman, and takes to Himself also the sufferings due to sin (yet is not Himself a sinful man, and is God unchanged in His being). In Christ, the two natures of God and human are not two persons but one; thus, a union is effected in Christ, between all of humanity and God. So, the holy God and sinful humanity are reconciled in principle, in the one sinless man, Jesus Christ. (See Jesus's prayer as recorded in John 17.)
This reconciliation is made actual through the struggle (podvig in Russian) to conform to the image of Christ. Without the struggle, the praxis, there is no real faith; faith leads to action, without which it is dead. One must unite will, thought and action to God's will, His thoughts and His actions. A person must fashion his life to be a mirror, a true likeness of God. More than that, since God and humanity are more than a similarity in Christ but rather a true union, Christians' lives are more than mere imitation and are rather a union with the life of God Himself: so that, the one who is working out salvation, is united with God working within the penitent both to will and to do that which pleases God. Gregory Palamas affirmed the possibility of humanity's union with God in His energies, while also affirming that because of God's transcendence and utter otherness, it is impossible for any person or other creature to know or to be united with God's essence. Yet through faith we can attain phronema, an understanding of the faith of the Church.
The journey towards theosis includes many forms of praxis. Living in the community of the church and partaking regularly of the sacraments, and especially the Eucharist, is taken for granted. Also important is cultivating "prayer of the heart", and prayer that never ceases, as Paul exhorts the Thessalonians (1 and 2). This unceasing prayer of the heart is a dominant theme in the writings of the Fathers, especially in those collected in the Philokalia.
