In Eastern Orthodox and Eastern Catholic theology, theosis, meaning divinization (or deification or, to become god), is the call to man to become holy and seek union with God, beginning in this life and later consummated in the resurrection. Theosis comprehends salvation from sin, is premised upon apostolic and early Christian understanding of the life of faith, and is conceptually foundational in both the East and the West.
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. As God became man, in all ways except sin, He will also make man God, in all ways except His divine essence.
St. Maximus the Confessor wrote, "A sure warrant for looking forward with hope to deification of human nature is provided by the incarnation of God, which makes man god to the same degree as God Himself became man. For it is clear that He who became man without sin (cf. Heb. 4:15) will divinize human nature without changing it into the divine nature, and will raise it up for His own sake to the same degree as He lowered Himself for man's sake. This is what St. Paul teaches mystically when he says, '...that in the ages to come He might display the overflowing richness of His grace' (Eph. 2:7)."(page 178 PHILOKALIA Volume II)
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, 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. Using the head-body analogy from St. Paul every man in whom Christ lives in, partakes of the glory of Christ. As St. John Chrysostom observes "where the head is, the body is also; for by no means is the head separated from the body; for if it were indeed separated, there would not be a body and there would not be a head".
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. A common analogy for theosis, given by the Greek fathers, is that of a metal which is put into the fire. The metal obtains all the properties of the fire (heat,light) where its essence remains that of a metal.
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.
In Orthodox theology theosis is always a gift of Grace. Praxis or practice or even prayer doesn't deificate by itself but is means for expressing willingness to be saved and deified, and it is also means to receive Grace that deifies. Main 'doer' in deification is Holy Spirit not human being that is mostly 'receiver' or 'object' of theosis.
See also: Desert Fathers, Hesychasm, Maximus the Confessor, Monasticism
Some western writers refer to theosis using the same implications given above. It is common to find western writings that flatteringly suggest that eastern spirituality uniquely manifests theosis, and that by implication their own tradition never attained to the idea. This may be a case of rhetoric obscuring fact. Under different terminology the western spiritual traditions, which also reach to the origins of Christianity (in the East), share the objective of sharing in the life of God. Some Catholic writers consider it lamentable that the term theosis is not used more extensively in western theology.
It is, therefore, misleading to attribute to Eastern Orthodoxy a special insight into the possibility of union with God: from a western point of view, the theological difference between east and west is somewhat rhetorical. But there is also a slight difference in that what theosis actually means. In West there is a tendence to see theosis as mere union (purgation, illumination and union as model for deification), which is a half truth.
Whether or not eastern liturgies are more conducive to theosis is another matter. In the west there has been much discussion of the merits of the Mass of Paul VI, and some traditionalists claim that the Tridentine Mass is particularly conducive to the kind of prayer life that leads one along toward theosis. Virtually all spiritual books of any consequence published in the west manifest overt awareness of all the issues comprised in theosis (some books may focus on specific stages and treat unitive themes more briefly).
The doctrine of theosis or deification in The Church of Jesus Christ of Latter-day Saints differs significantly from that of orthodox Christian theology (note, not only Eastern Orthodox). In Mormonism it is usually referred to as exaltation or eternal life. Exaltation is to become, through the sacrifice of Christ, a co-inheritor with Jesus in all that the Father possesses. As children of God we are enabled to become one with God as Jesus is one with God.
While the primary focus of Mormonism is on salvation through the atonement of Jesus Christ, exaltation goes beyond mere salvation. All mankind will be saved from death through the resurrection of Jesus Christ, but only those who are sufficiently obedient, receive specific saving ordinances, and accept the atonement of Jesus Christ before the judgment will be exalted.
Eastern Orthodoxy | Eastern Rite Catholicism | Latter Day Saint doctrines regarding deity | Theology | Christian theology