From a traditional, Orthodox perspective, the doctrine of “deification” or “theosis” is essentially a doctrine of “salvation,” or what the 19th century Russian hermit, Seraphim of Sarov, called “acquisition of the Holy Spirit.”
In contra-distinction from the recent Mormon heterodoxy of “exaltation” or “eternal progression,” the Orthodox doctrine of theosis teaches that man can be united to God in his “energies,” but not in his “essence,” a foundational Greek distinction of the early Church. This means that when one speaks of theosis, one is not speaking of the idea that God is essentially – whether in actuality or potentially – a part of all things (pantheism), but rather that mankind can participate in the grace or energies of the Trinity by virtue of one’s union with Jesus Christ, as well as one’s faithful participation in the mysteriological life of the Church.
Of that participation in both Christ and his body (the Church), the “catalyst” for this participation is the mystery of holy baptism.
According to the Latin tradition, this gift of the life of God in baptism is “infused by the Holy Spirit into our soul to heal it of sin and to sanctify it. It is the sanctifying or deifying grace received in Baptism. It is in us the source of the work of sanctification” (Catechism of the Catholic Church, 1999). This work of sanctification in the baptized Christian is the means by which a person becomes “a new creation,” with “the old” passing away and “the new” taking its place (2 Cor. 5:17). The sanctifying grace of Christ – a participation in the very life of Christ – goes beyond a merely extrinsic pronouncement, but is in fact an effectual and real change of the baptized person in their very being. One is not merely “counted” to be righteous in Christ, as if it were simply a “legal fiction”; rather, one is transformed through a “participation in the life of God” (Ibid., 1997).
By suffering with Christ, one can be “glorified with him” (Rom. 8:17); by “escaping the worldly corruption that is produced by evil desire,” one may join with those who are “partakers of the divine nature” (2 Pet. 1:4). Just as the Son and the Father are one (John 17:21), the Lord Jesus Christ prays for his Church that they would “dwell in the Trinitarian God,” sharing in the very life of the Trinity for the sake of their salvation, a reoccurring theme in the fourth gospel (Ware, The Orthodox Church, p. 231). Therefore, theosis begins as the union of a person with the Godhead through the waters of baptism. One is “born again” and “from above” (John 3:3), being re-born of both “water” and “spirit” (John 3:5).
While one’s new life in Christ begins with baptism, the continuation or “maturity” of this life (Matt. 5:48), as a participation in the life of the holy Trinity, is characterized as “synergy” or the cooperation of a person’s will with God. This maturation, which is made complete in “glorification,” is the process through which one “trains” one’s gnomic will to discern between both “good and evil” (Heb. 5:14).
On this doctrine of synergy, the second Council of Orange, held on July 3, 529, concluded:
According to the catholic faith, we also believe that after grace has been received through baptism, all baptized persons have the ability and responsibility, if they desire to labor faithfully, to perform with the aid and cooperation of Christ what is of essential importance in regard to the salvation of their soul.
Since the apostle Paul instructs the Corinthians that “no one can say, ‘Jesus is Lord,’ except by the Holy Spirit,” (1 Cor. 12:3), it must be understood that all sanctification (leading to theosis) after baptism is the result of one’s cooperation with God, and not as a result of the “merit” of the individual in question; that is, as being done apart from the life of Christ and his holy Church. The apostle Paul offers a balance between both the responsibility of man and the assistance of God (in synergy) in his letter to the Philippian church: “Therefore, my beloved … work out your own salvation with fear and trembling; for it is God who works in you both to will and to do for His good pleasure” (Phil. 2:12).
As mentioned previously, theosis does not describe a change in the essence of a person to that of the Godhead, but rather a person’s partaking of the “divine nature,” along with a transformative experience of the energies of God. The distinction between the two can become tedious, but it is certainly necessary, as the idea of deification has often carried with it a history of controversy and misunderstanding. For example, when Jesus quotes Psalm 82:6 to the Jewish leaders – “you are gods” (John 10:34) – their reaction is an enraged attempt to arrest him (John 10:39).
Nevertheless, the fruit of theosis is seen in its full glory in the transfiguration of Christ (Luke 9:28-36). The Lord’s revelation of this eschatological state of being is shown to them as a snapshot of “the kingdom of God” (Luke 9:27), which is, at the same time, a both future and present experience in the life of the Church. The apostle Peter’s instinct at this event is to construct a “booth” or “tabernacle” for the Lord (as well as for both Moses and Elijah), no doubt wishing to provide them a place for their commemoration of the feast of Tabernacles (Luke 9:33). While the apostle might have missed the immediate meaning of this revelation of the transfiguration, it appears that he later made the connection between the transfiguration of Christ and that of Christians in his Church, who live and serve as sacrificial (Rom. 12:1) temples of the Holy Spirit (1 Cor. 6:19-20): “Indeed, as long as I am in this tabernacle, I consider it right to stir you up by way of a reminder, since I know that my tabernacle will soon be removed, because our Lord Jesus Christ revealed this to me” (2 Pet. 1:13-14). After this admission of his impending death (the removal of his “tabernacle”), the apostle recounts his experience on the mountain of the Lord’s transfiguration (2 Pet. 1:16-18). The connection between the glory that is revealed in Christ’s transfiguration, and the future experience of faithful Christians in their own glorification – an experience of the future “kingdom of God” – should be noted.
Finally, it is worth considering that the doctrine of theosis tells us a great deal about the relationship between both God and his creation, since “not only our human body but the whole of the material creation will eventually be transfigured” (Ware, The Orthodox Church, p. 234).
Indeed, the apostle Paul makes explicit mention of the fact that the whole of creation is awaiting the transformation found in Christ and his resurrection (Rom. 8:19-22), which will remove from all life the stains of both death and corruption. At the heart of this transformation of creation, of course, is the doctrine of the incarnation of Jesus Christ, of which Saint Athanasius the Great famously asserted: “He was made man that we might be made god” (On the Incarnation, 54:3). The incarnation informs a doctrine of theosis that is concerned with the transformation of body, soul, and spirit, and not of one’s soul or spirit alone, along with an inherent concern for the redemption of the material world.
The first fruits of this “cosmic redemption” in Christ can be seen in the icons of the Church, examples of matter that have been redeemed in Christ and which can therefore serve as “windows into heaven,” or a foretaste of the future “kingdom of God.” The purpose of the Christian life, therefore, is not to wholly renounce and “escape” this world, but to aid in its transformation through the love and work of Christ. Christ will come to “make all things new,” (Rev. 21:1) but not to “make all new things.” Our concern and care for this world – animals, trees, and everything in between – is intimately connected with a proper understanding of our own union with the risen Christ, who wrapped himself with creation and redeemed it from corruption through his triumph over death.
In conclusion, it can be stated simply (along with Seraphim of Sarov) that theosis or “salvation” is, again, an “acquisition of the Holy Spirit.”
Through our union with Christ, the true Temple (or “tabernacle”), we become (as the Church) a “temple of the living God” (2 Cor. 6:16). Just as the old covenant temple served as a dwelling place for the glory of God, so too does our new covenant temple, which is the body of Christ. This union with the Godhead serves as the means by which we are transformed, cooperating with the divine energies and conforming our fallen will to more frequently choose that which is good and pleasing in the Lord’s sight (Heb. 5:14). By becoming like Christ, one can fulfill the calling that begins in baptism: being united with Christ in his death (as co-heirs of suffering, cf. Rom. 8:17), Christians are united with him in his transfiguration and resurrection, as well.
To see “the kingdom of God” in its fullness is to achieve theosis in its fullness, just as the Lord demonstrated for his disciples on the mountain.