The imagery of light plays a key role in Basil of Caesarea’s narrative of God and salvation. Curiously, the communal aspects of this imagery have received little attention in scholarship. A systematic analysis of “De Spiritu Sancto” reveals that in Basil’s understanding, participation in divine light functions as a parallel concept to Church membership. To begin with, the corporate nature of participation in divine light is evident from the ecclesial rites of initiation whereby this participation is bestowed. Furthermore, Basil uses the imagery of light to underscore the corporate nature of both the mystical union between God and the baptized, and the outward expressions of the believers’ lives in the divine light: worship and public witness. In addition to shedding new light on the Basilian notion of Church membership, the study o#ers a fresh outlook into the ecumenical dialogue between the Orthodox Church and Lutheran Church bodies on the theology of initiation.