Theosis (Eastern Orthodox theology)

Theosis or deification is a transformative process whose aim is likeness to or union with God, as taught by the Eastern Orthodox Church and Eastern Catholic Churches. As a process of transformation, theosis is brought about by the effects of catharsis (purification of mind and body) and theoria ('illumination' with the 'vision' of God). According to Eastern Christian teaching, theosis is very much the purpose of human life. It is considered achievable only through a synergy (or cooperation) between human activity and God's uncreated energies (or operations).

According to Metropolitan Hierotheos Vlachos, the primacy of theosis in Eastern Christian theology is directly related to the fact that Eastern Christian theology (as historically conceived by its principal exponents) is based to a greater extent than Roman Catholic theology on the direct spiritual insights of the saints or mystics of the church rather than the apparently more rational thought tradition of the West. Eastern Christians consider that "no one who does not follow the path of union with God can be a theologian" in the proper sense.

Theology in Eastern Christianity is not treated primarily as an academic pursuit. Instead it is based on applied revelation (see gnosiology), meaning that Eastern Christian theology and its theologians are validated by a holy and ascetical life rather than by intellectual training or academic credentials (see scholasticism).

St. Athanasius of Alexandria wrote, "He was incarnate that we might be made god" (Αὐτὸς γὰρ ἐνηνθρώπησεν, ἵνα ἡμεῖς θεοποιηθῶμεν). His statement is an apt description of the doctrine. 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: as it is not possible for any created being to become God ontologically, or even a necessary part of God (of the three existences of God called hypostases), so a created being cannot become Jesus Christ, the Holy Spirit nor the Father of the Trinity.

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