In the Orthodox Church, salvation is primarily understood as theosis. Theosis is the infinite process of becoming more and more united with God; being conformed more and more to God’s image and likeness. Theosis means that the Christian can become more and more saturated with the divine life, becoming by grace what Christ is by nature. As St. Athanasius the Great (4th century) put it, “God became man so that man might become divine.” In being united to the incarnate Christ, we become like Christ. We become temples of the Holy Spirit (I Cor. 6:19), partakers of the divine nature ( II Pet. 1:4). We do not become new Christs—new gods—nor do we lose our humanity or our identity. Rather, by God’s grace—and because the Word became incarnate as a human being, was crucified, died, was buried, was risen from the dead, and ascended into the heavens, and is seated at the right hand of the Father—we are united, to an ever greater and greater degree, with the One God who is all in all.

Becoming like Christ is about much more than just where we go when we die. For the Orthodox, salvation is a process that sanctifies not only the eternal life of the age to come, but the whole earthly life of the Christian. It is only in and through Christ that we can be saved (John 14:6). Salvation cannot be earned. It’s a free gift from God. We cannot merit union with the eternal God. At the same time, salvation assumes our cooperation with God, because God will not violate our free will. A life of repentance - that is, a joyful turning away from our sin and toward the merciful and loving God - along with participation in the sacraments, like baptism and holy communion, is how we synergistically cooperate with God. God’s grace not only forgives sins and conquers death, through Christ’s atoning sacrifice on the cross; but also makes us more like Christ, theosis. Through God’s grace working in us, we work out our salvation in cooperation with Him (Phil. 2:12). This cooperation is called synergy (synergeia), making us co-workers with God (I Cor. 3:9; II Cor. 6:1).

In theosis, we become filled with the divine light and life. We take on God’s attributes, but we do not become merged with the Holy Trinity. We become partakers of the divine nature (II Peter 1:4), but not God’s essence. There is union but without fusion. The Church proclaims that we can become like God by grace, not in a polytheistic sense (there is only one God), but rather we become adopted sons and daughters of the Most High (Ps. 82:6; John 10:34), like our Creator but not identical with Him. In becoming like God, we do not lose our human identity, but acquire His light and life. A classic image of theosis from Church history is a sword held in a flame; the sword gradually takes on the properties of the flame (light and heat), but it remains a sword. Our salvation is for all things—our humanity, our love, the image and likeness of God in us—to be gathered together in Christ (Eph. 1:10, 2:6).

The Church also speaks of salvation as adoption, as atonement, as healing, as ransom, as having a debt paid, as having transgressions pardoned, etc. These are all good and helpful images, but theosis is the primary image through which salvation is understood.