The chapter explores connections between two phenomena: theosis and the church. Initially, such connections were not obvious, as the notion of the church was rudimentary and expressed mainly through metaphors. One may discern early metaphors referring to the church and theosis, such as the images of the second Adam and recapitulation. Pseudo-Dionysius the Areopagite introduced a new way of thinking about the church and theosis. This way was restrictive and hierarchical. The adoption of dialectical categories by the Christian theology advanced the understanding of theosis and its connectedness with the church. Theologians, especially in the East, came to distinguish between the common potentiality and particular actuality of deification. The former, which they called isotheon, transformed to the latter, theosis in the church. The Russian religious philosophy provided a framework for a modern synthesis between the ideas of the Incarnation, the church, and deification.