What do Orthodox Christians mean by „theosis”?

For the Orthodox Church, salvation is not only the forgiveness of sins or an acquittal from a distance, but participation in God himself. The Fathers call this theosis, deification: the human person, united to Christ, is filled with the uncreated life, light and glory of the Holy Trinity, becoming god by grace while God alone remains God by nature.

The teaching is biblical. St Peter writes that God „has granted to us his precious and very great promises, that through these you may become partakers of the divine nature” (2Pe 1:4). The Lord prays „that they may be one; even as you, Father, are in me, and I in you, that they also may be in us” (Joh 17:21). The calling was written into our very making: „Let us make man in our image, after our likeness” (Gen 1:26). The image is given; the likeness is the goal toward which we grow.

St Athanasius summarized the whole Gospel in one sentence: „God became man so that man might become god.” Theosis is not achieved by human effort alone but received as a gift, through Baptism and the Eucharist, prayer, repentance and the keeping of the commandments, in cooperation with the grace of the Holy Spirit. Its fulfillment is the promise of Christ: „One who overcomes, I will grant to sit down with me on my throne” (Rev 3:21).