For the Orthodox, salvation is a process that encompasses not only the whole earthly life of the Christian, but also the eternal life of the age to come. It is often described in terms of three stages—purification (katharsis), illumination (theoria) and divinization (theosis). Salvation is therefore not only becoming sinless (purification), but it is also progress in being filled with the divine light (illumination). And it is becoming so filled with God in union with Him that we shine with the likeness of God. In some cases that means even literally becoming a bearer of the Uncreated Light, which is a physically visible light from God that is His presence, such as at the Transfiguration (Matt. 17:1-6; Mark 9:1-8; Luke 9:28-36) or when Moses spoke with God on Mt. Sinai (Ex. 34:29-35). Though this terminology of three stages is sometimes used, there is overlap between them, and the whole process itself is also called theosis.
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. But being saved requires our cooperation with God, because God will not violate our free will. A life of repentance is needed—that’s turning away from our sin and toward God. Along with repentance, participation in the sacraments, like baptism and holy communion, is how we cooperate with God. God’s grace not only forgives sins through Christ’s atoning sacrifice on the cross but also makes us more like Christ. 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 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). There is union but without fusion. We say that we can become a “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 Father but not the same as Him. 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 goal is for all things to be gathered together in Christ (Eph. 1:10, 2:6).
The Church also speaks of salvation as adoption, as atonement, as healing, as substitution by Christ, as sacrifice, as having a debt paid, as having crimes pardoned, etc., but theosis is the primary model through which salvation is understood. We’ve talked a lot about the Church. So what is the Church?
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Adapted from St. Paul Antiochian Orthodox Church in Emmaus, Pennsylvania.