‘Deification’ (Gk. ‘theosis‘) is a term widely used in Eastern Orthodox theology for the process by which God’s grace transforms believers into his likeness.  It involves belief that grace reverses the effects of the Fall, and confers on the believer the ‘divine’ attributes of incorruptibility and immortality.  But

‘its central tenet is that God through the Incarnation of his Son has called men to share the Divine life in the Son.’ (Oxford Dictionary of the Christian Church, art. ‘Deification’)

The Orthodox often appeal to the famous statement of Athanasius, who declared that God became man in order that we might become divine.

I cite at length the explanation from The Orthodox Study Bible, 2008, by St. Athanasius Academy of Orthodox Theology:

Deification is the ancient theological word used to describe the process by which a Christian becomes more like God. St. Peter speaks of this process when he writes, “As His divine power has given to us all things that pertain to life and godliness . . . you may be partakers of the divine nature” (2 Pet 1:3, 4).

What does it mean to partake of the divine nature, and how do we experience this? To give an answer, let us first address what deification is not, and then describe what it is.

What deification is not. When the Church calls us to pursue godliness, to be more like God, this does not mean that human beings become divine. We do not become like God in His nature. That would not only be heresy, it would be impossible. For we are human, always have been human, and always will be human. We cannot take on the nature of God.

St. John of Damascus makes a remarkable observation. The word “God” in the Scriptures refers not to the divine nature or essence, for that is unknowable. “God” refers rather to the divine energies—the power and grace of God that we can perceive in this world. The Greek word for God, theos, comes from a verb meaning “run,” “see,” or “burn.” These are energy words, so to speak, not essence words.

In John 10:34, Jesus, quoting Psalm 81:6, repeats the passage, “You are gods.” The fact that He was speaking to a group of hypocritical religious leaders who were accusing Him of blasphemy makes the meaning doubly clear: Jesus is not using “god” to refer to divine nature. We are gods in that we bear His image, not His nature.

What deification is. Deification means we are to become more like God through His grace or divine energies. In creation, humans were made in the image and likeness of God (Gn 1:26) according to human nature. In other words, humanity by nature is an icon or image of deity: The divine image is in all humanity. Through sin, however, this image and likeness of God was marred, and we fell.

When the Son of God assumed our humanity in the womb of the blessed Virgin Mary, the process of our being renewed in God’s image and likeness was begun. Thus, those who are joined to Christ, through faith, in Holy Baptism begin a process of re-creation, being renewed in God’s image and likeness. We become, as St. Peter writes, “partakers of the divine nature” (2 Pet 1:4).

Because of the Incarnation of the Son of God, because the fullness of God has inhabited human flesh, being joined to Christ means that it is again possible to experience deification, the fulfillment of our human destiny. That is, through union with Christ, we become by grace what God is by nature—we “become children of God” (Jn 1:12). His deity interpenetrates our humanity.

Historically, deification has often been illustrated by the example of a sword in the fire. A steel sword is thrust into a hot fire until the sword takes on a red glow. The energy of the fire interpenetrates the sword. The sword never becomes fire, but it picks up the properties of fire.

By application, the divine energies interpenetrate the human nature of Christ. When we are joined to Christ, our humanity is interpenetrated with the energies of God through Christ’s glorified flesh. Nourished by the Body and Blood of Christ, we partake of the grace of God—His strength, His righteousness, His love—and are enabled to serve Him and glorify Him. Thus we, being human, are being deified.

Note: No justification is given for the assertion that,

‘the Greek word for God, theos, comes from a verb meaning “run,” “see,” or “burn.” These are energy  words, so to speak, not essence words.’

Perhaps it comes from a discourse between Socrates and Hermogenes in “Cratylus”, in which Socrates says:

‘It seems to me that the earliest people in Greece had a notion of only those gods whom the majority of barbarians now recognize: the Sun, the Earth, the Stars, and the Sky. Now, because they noticed that these things were always moving in a circle and ‘running’ (theonta), they called them gods (theous) from the nature of that running (thein). Later, once they came to acknowledge the existence of other gods, they continued to use the same word, ‘gods’ for them as well.’

It is of interest that the quotation above comes from a web site called, ‘Adventures in Preposterous Etymology’!

According to Timothy Ware (The Orthodox Church), Orthodoxy finds scriptural support for deification in Jn 17:21 – “as You, Father, are in Me and I in You, so also may they be in Us”, and in Paul’s oft-repeated idea of believers being ‘in Christ’.

Following the teaching of St. Gregory Palamas, Orthodoxy insists that we can become like God in his energies, but not in his essence.  This distinction offers one way of protecting the doctrine against the charge of pantheism.

Robert Letham remarks, concerning the the earlier work of Athanasius and Cyril, that for them

‘Theōsis encompasses under one umbrella what in Reformed theology is understood to occur in the entire movement of God’s grace in transforming us into his image in Christ: regeneration, sanctification, and glorification combined.’

This is in contrast to the teaching of Origen and Gregory of Nyssa, which came close to ‘apotheosis’.  For them,

‘salvation entails being absorbed into God, individuals losing their identity as they are merged into this deified humanity.’

Ware insists:

‘Unlike the eastern religions which teach that humans are swallowed up in the deity, Orthodox mystical theology has always insisted that we humans, however closely linked to God, retain our full personal integrity. The human person, when deified, remains distinct (though not separate) from God.’

The church in the West has tended to express something similar in terms of adoption, ‘union with Christ’ and the ‘indwelling of the Holy Spirit’.  Such terminology is much more widely used in Scripture than ‘deification’ (for which  heavy reliance is made on just one text – 2 Peter 1:3).  It is also much less misleading (‘deification’ immediately suggests the heretical idea of ‘becoming God’, rather than ‘becoming like God’.

According to Bradley Nassif  (Three Views on Eastern Orthodoxy and Evangelicalism), the Orthodox understanding of deification explains why such a strong link is forged, in that theological tradition, between incarnation and salvation, and then on to the implications for the doctrines of the Trinity, church, Bible, sacraments, icons and so on.  Absolutely central is the affirmation that ‘the Word became flesh and made his dwelling among us’ (Jn 1:14).

Similarly Ware explains that deification involves the body.  Since Christ has saved the whole person, the body is deified along with the soul.  ‘Your body is a temple of the Holy Spirit’ (1 Cor 6:19); ‘Offer your bodies as a living sacrifice to God’ (Rom 12:10).  To be sure, the full deification of the body must wait until the last day, and the splendour of the saints in this life is largely an inner splendour.  But, even so, some saints have experienced in some measure of bodily glorification in this life.  The best-known example is St Seraphim, whose disciples saw ‘just like fire’ as he was praying.

If deification involves the body as well as the soul, it follows (in Orthodox thinking) that the relics of the saints merit great reverence.  Ware writes:

‘Like Roman Catholics, [Orthodox] believe that the grace of God present in the saints’ bodies during life remains active in their relics when they have died, and that God uses these relics as a channel of divine power and an instrument of healing. In some cases the bodies of saints have been miraculously preserved from corruption, but even where this has not happened, Orthodox show just as great a veneration towards their bones. This reverence for relics is not the fruit of ignorance and superstition, but springs from a highly developed theology of the body.’

As Nassif observes, when Protestants emphasise the place of ‘Christus Victor’ in their understanding of the agonement, they are close to the Orthodox understanding.  Moreover, some streams of Evangelical piety seem to reflect something like ‘deification’, as in Welsey’s famous lines: ‘Changed from glory into glory/till in heaven we take our place.’