The Definition and the Vocabulary

Theosis is the Church’s name for the end of human life: the real participation of the whole person — body, soul, and nous — in the life of God, so that the creature becomes god by grace what Christ is God by nature. This file fixes the Greek vocabulary, states the working definition and the asymmetry that governs it, and marks off at the outset the four claims the word does not make.

Tradition: Pan-Orthodox

The Words

The Greek tradition has a small family of terms, and the differences among them are worth keeping.

θέωσις (theosis) is the noun that became standard. It is not a New Testament word; it is a coinage of the Greek Fathers, and its establishment as the technical term is usually credited to the Dionysian corpus and to St. Maximus the Confessor, who uses it constantly (Russell, The Doctrine of Deification in the Greek Patristic Tradition, Oxford, 2004, 1–3, 33–40). St. Dionysius the Areopagite defines it functionally: deification is “the attaining of likeness to God and union with him so far as is possible” (Dionysius, The Ecclesiastical Hierarchy I.3; see St. Dionysius the Areopagite). The qualifier — so far as is possible — is not politeness. It is the whole doctrine in a subordinate clause.

θεοποίησις (theopoiesis), “god-making,” is the earlier and blunter term, the one St. Athanasius prefers. It is the word behind his verb theopoiethomen, “that we might be made god” (Athanasius, On the Incarnation 54.3; see St. Athanasius: Theosis in Athanasius).

θείωσις (theiosis), “divinization,” and the verbal forms theoumai / theoumenos also occur; St. Gregory the Theologian’s definition of the human being as ζῷον θεούμενον, “a living creature that is being deified,” uses the present passive participle, and the tense is load-bearing (Gregory of Nazianzus, Oration 38.11; the phrase and its grammar are analysed at Panayiotis Nellas: A Living Creature Being Deified).

The Latin deificatio and the English deification and divinization render the same thing. English readers should note that the older English theological vocabulary largely lost the word, which is one reason the doctrine came to be regarded as an Eastern peculiarity — a historical judgment now heavily qualified by scholarship (Gavrilyuk, “The Retrieval of Deification: How a Once-Despised Archaism Became an Ecumenical Desideratum,” Modern Theology 25, no. 4 [2009]: 647–659; discussed at The Modern Retrievals).

The Working Definition

Theosis is the transformation of the human person by uncreated grace into a real participant in the divine life, begun in this life through Baptism, Chrismation, and above all the Eucharist, advanced through the free cooperation of the person with grace in the keeping of the commandments and in prayer, and consummated in the age to come — a participation in the divine energies, never in the divine essence, so that the creature is truly united to God without ever ceasing to be a creature.

Every clause of that sentence is doing work.

“Real participation.” Theosis is not a metaphor for moral improvement and not a legal fiction. The Church’s claim is ontological: something happens to the human being, and what happens is that he is filled with God. St. Maximus states the ground of the confidence: “A sure warrant for looking forward with hope to the deification of human nature is provided by the incarnation of God, which makes man god to the same degree as God himself became man” (Maximus, Various Texts on Theology, the Divine Economy, and Virtue and Vice 1.62, in The Philokalia, vol. 2, trans. Palmer–Sherrard–Ware — a Byzantine compilation drawn from Maximus’ works; the theme pervades Ambiguum 7).

“By uncreated grace.” What is given in theosis is not a created gift that God produces and hands over. It is God himself in his self-communication — his glory, his light, his life, his energy. This is the point on which the Orthodox account turns, and it was defined conciliarly in the fourteenth century (Synodal Tome of 1351, in Russell, trans., Gregory Palamas: The Hesychast Controversy and the Debate with Islam, Liverpool, 2020; see Essence and Energies). If grace were created, then in receiving grace the creature would receive a creature, and union with God would be union with something that is not God.

“The whole human person.” Theosis is not the escape of a soul from a body. The body is deified with the soul; this is why the Church confesses the resurrection of the body, venerates the relics of the saints as sanctified matter, and holds that the hesychast can see the uncreated light with bodily eyes transformed by the Spirit (Synodal Tome of 1351, in Russell 2020; cf. Theological Anthropology).

“Begun in this life.” Deification is not exclusively a post-mortem reward. St. Nicholas Cabasilas makes the point programmatically: the life in Christ originates here and is perfected in the age to come, and its beginning is sacramental, not visionary (The Life in Christ, Book I; trans. deCatanzaro, SVS Press, 1974; see St. Nicholas Cabasilas: Union with Christ).

“Consummated in the age to come.” And never completed. Because God is infinite, the creature’s approach to him has no terminus; St. Gregory of Nyssa’s epektasis means that the blessed do not arrive but ascend endlessly from glory to glory (see The Patristic Witness).

The Governing Asymmetry: By Grace, Not By Nature

The single formula that keeps the doctrine orthodox is that the deified become by grace what God is by nature. It is Athanasian in substance and Maximian in phrasing, and it is repeated by every subsequent teacher of the doctrine.

St. Athanasius marks the asymmetry sharply and for a polemical reason. The whole anti-Arian argument depends on it: if creatures could become gods by nature, the line between Creator and creature would blur and the Son’s own divinity would prove nothing; but precisely because we become gods only by participation and gift, the Word who deifies must himself be God by nature, on the far side of that line (Athanasius, Contra Arianos 1.9; 3.19–20; trans. NPNF II/4). The Son is Son by nature (physei); we are made sons by adoption, receiving the Spirit of the Son so that we can cry “Abba, Father” (Romans 8:15; Athanasius, Contra Arianos 1.37–39; 2.59).

The classical image of the asymmetry is iron in fire. Iron placed in the furnace becomes incandescent: it glows, it burns, it does everything fire does, and yet it remains iron and does not become fire. So the deified person is wholly permeated by divine energy while remaining a creature — the analogy St. Maximus uses and St. Gregory Palamas inherits (Maximus, Ambigua 7; cf. Theosis; St. Gregory Palamas: The Essence-Energies Distinction).

The capital letter is therefore not a typographical fussiness. The Fathers say that we become gods, and the Church says it after them; they do not say that we become God.

What the Word Does Not Claim

Four denials belong to the definition itself, and stating them early prevents most misreadings. They are developed at length in What Theosis Is Not.

It does not claim participation in the divine essence. The ousia of God is imparticipable — not merely unknown to us in fact, but by nature beyond all participation and comprehension. No creature, no saint, no angel ever knows or shares in the essence of God. What is participated is the uncreated energy (Synodal Tome of 1351, in Russell 2020; Lossky, The Mystical Theology of the Eastern Church, Cambridge, 1957, ch. 4).

It does not claim absorption. The deified person is not dissolved into God as a drop into the ocean. Personal identity is not erased but perfected; freedom is not overridden but healed; consciousness is not extinguished but flooded with light. Lossky’s summary is that the way of deification is the way of union of the human person with God — not the annihilation of the human but its fulfilment (Lossky 1957, ch. 10, “The Way of Union”; cf. Soteriology).

It does not claim that deification is automatic. Theosis is synergistic. Grace is prior, sovereign, and gratuitous; and it does not act on the human person as on a stone. The possibility of refusal is real throughout (see Synergy and the Mysteries).

It does not claim a merely moral achievement. The commandments are indispensable, but theosis is not the sum of virtues acquired. It is God’s act on a creature who consents. Nellas’s often-quoted line makes the point from the anthropological side: “the spiritual life is not a life of laws and precepts but a life of participation, affection and love, a life of mingling and mixing with God” (Nellas, Deification in Christ, trans. Russell, SVS Press, 1987, 116).

Why the Doctrine Is Central and Not Exotic

It is sometimes said that theosis is a specialty of Eastern monasticism. That is a misdescription on two counts.

First, the doctrine is not monastic in origin or in scope. It is the Church’s account of why God became man, and it is therefore inseparable from the Creed. St. Athanasius’ argument from deification is an argument about the homoousion; St. Gregory the Theologian’s “the unassumed is the unhealed” is an argument about the completeness of Christ’s humanity (Gregory of Nazianzus, Epistle 101, to Cledonius); St. Cyril’s Eucharistic realism is an argument about how the deifying flesh of the Word reaches us. Take theosis out and the councils lose their point.

Second, the doctrine is not reserved to contemplatives. Cabasilas wrote The Life in Christ for Christians in the world, locating deification not in a rare contemplative ascent but in the Mysteries available to every baptized person (Russell 2004, 304–306; see St. Nicholas Cabasilas: The Sacramental Life). Bishop Kallistos Ware put the pastoral form of the point plainly: the vocation to deification is universal, given to every Christian at baptism, and the ascetic tradition exists to serve it rather than to restrict it (Ware, The Orthodox Way, rev. ed., Crestwood, NY: SVS Press, 1995; see Kallistos Ware).

The word is unfamiliar in English. The thing it names is the ordinary Christian life brought to its end.

References

Athanasius of Alexandria. On the Incarnation, 54. Trans. NPNF II/4; cf. John Behr, trans., Popular Patristics Series. Crestwood, NY: SVS Press.
Athanasius of Alexandria. Orations against the Arians, 1.9, 1.37–39, 2.59, 3.19–20. Trans. NPNF II/4.
Dionysius the Areopagite. The Ecclesiastical Hierarchy I.3.
Gregory of Nazianzus. Oration 38.11; Epistle 101 (to Cledonius).
Gavrilyuk, Paul L. “The Retrieval of Deification: How a Once-Despised Archaism Became an Ecumenical Desideratum.” Modern Theology 25, no. 4 (2009): 647–659.
Lossky, Vladimir. The Mystical Theology of the Eastern Church. Cambridge: James Clarke, 1957. Esp. chs. 4 and 10.
Maximus the Confessor. Ambigua, 7. Various Texts on Theology, the Divine Economy, and Virtue and Vice 1.62, in The Philokalia, vol. 2, trans. G. E. H. Palmer, Philip Sherrard, Kallistos Ware. London: Faber, 1981.
Nellas, Panayiotis. Deification in Christ: Orthodox Perspectives on the Nature of the Human Person. Trans. Norman Russell. Crestwood, NY: SVS Press, 1987.
Nicholas Cabasilas. The Life in Christ. Trans. Carmino J. deCatanzaro. Crestwood, NY: SVS Press, 1974.
Russell, Norman. The Doctrine of Deification in the Greek Patristic Tradition. Oxford Early Christian Studies. Oxford: Oxford University Press, 2004.
Russell, Norman, trans. Gregory Palamas: The Hesychast Controversy and the Debate with Islam. Documents Relating to Gregory Palamas. Translated Texts for Byzantinists 8. Liverpool: Liverpool University Press, 2020. (Includes the Synodal Tome of 1351.)
Ware, Kallistos. The Orthodox Way. Rev. ed. Crestwood, NY: SVS Press, 1995.