Theosis: Becoming by grace what God is by nature.
The Orthodox Church does not accept the doctrine of original sin as espoused in the West, yet this in no way suggests that we do not need to be born anew. We Orthodox believe, as did the early Church Fathers, that we inherit only the results of Adam’s sin, not his guilt. This is known as ancestral sin because the sin of our first parents, Adam and Eve, resulted in our inheritance of death, sickness, and an inclination towards evil. Christ’s death on the cross has its power, not in an atonement sacrifice, but in the conquering of the power of death. Death is trampled down by the death of Christ, and the permanency of death is destroyed by Christ’s resurrection. It is by Christ’s resurrection that a way was made for us to be transformed by contact with the living God, and made his children by adoption.
It is by his condescension to join himself to his creation that we humans are given the opportunity of being deified, and our journey into the heart culminates in theosis, whereby we are joined in everlasting communion with the very God who created us. St. Athanasius of Alexandria said, “The Son of God became man, that we might become god.” And in 2 Peter 1:4, we read that we have become “partakers of divine nature.” St. Athanasius further says that theosis is “becoming by grace what God is by nature.”