Theosis (deification)

Athanasius's sentence, written in the fourth century while he was defending the full divinity of Christ against Arianism, is the compressed form of the whole doctrine, and the argument runs backwards from salvation to christology. If what happens to human beings in salvation is that they are drawn into the life of God, then the one who effects it must himself be God; a creature, however exalted, could not confer what it does not possess. Theosis is thus the reason Eastern theology insisted on Nicaea, and not a later mystical addendum to it.

The scriptural anchor is the Second Letter of Peter, which speaks of becoming partakers of the divine nature, together with the line from the eighty-second Psalm that John's gospel puts on Jesus's lips, I said, you are gods. Irenaeus, Athanasius, Gregory of Nyssa and Maximus the Confessor all state the theme, and the last works out its christological logic in detail: because in Christ divine and human wills coexist without competition, human nature is not diminished by union with God but perfected.

The obvious danger is pantheism, and the Eastern answer was given definitively by Gregory Palamas in the hesychast controversies of the fourteenth century. Palamas distinguished God's essence, which is utterly inaccessible and in which no creature ever shares, from God's energies, his uncreated activity and self-communication, which are truly God and in which the creature genuinely participates. The deified person therefore becomes by grace what God is by nature, and the distinction between creator and creature is never crossed. Palamas was defending the hesychast monks who claimed to see the uncreated light of Tabor in prayer; his opponent Barlaam held that any such vision would have to be created, and the councils of the 1340s decided for Palamas.

Theosis is not the Latter-day Saint doctrine of exaltation, though the two are often paired in popular comparisons and the similarity of phrasing is real. Latter-day Saint teaching holds that God and human beings are of the same order of existence and that the faithful may become gods in the fullest sense. Theosis denies precisely that: the divine essence is never shared, human nature is never abolished or transcended into deity, and the participation is in God's energies by grace. The two doctrines use overlapping words to make incompatible claims.

Nor is it identical to the Western language of sanctification, though the difference is one of emphasis and framing rather than contradiction. Western theology, from Augustine onward, organised salvation around guilt, its remission and the restoration of a right standing, and made justification a forensic category at the centre. Eastern theology organised it around mortality and corruption, with the incarnation as the point at which divine life enters and heals a nature subject to death. The East never developed a doctrine of inherited guilt in the Augustinian sense, holding that what is inherited is mortality and its consequences rather than culpability, which is one reason the Immaculate Conception looked to Orthodox theologians like an answer to a question they had not asked.

In practice theosis is what Orthodox asceticism is for. The hesychast tradition, the Jesus Prayer, the writings collected in the Philokalia, the monastic life of Mount Athos and the veneration of icons all presuppose that the human person is being remade and can be transfigured now, which is why the saints are depicted as luminous rather than merely virtuous. The Oriental Orthodox churches teach the same, and modern Catholic theology has recovered the vocabulary; the Catechism of the Catholic Church quotes Athanasius's sentence directly.