In Behold the Pierced One, Joseph Ratzinger recounts how the composition of a 1981 paper on the Sacred Heart of Jesus had led him to "consider Christology more from the aspect of its spiritual appropriation" than he had done previously. Upon realizing that this same year was the 1300th anniversary of the Third Council of Constantinople, he decided to study the pronouncements of this Council, and came to believe "that the achievement of a spiritual Christology had also been the Council's ultimate goal." Ratzinger's conclusion in attempting to define a spiritual Christology was that "the whole of Christology--our speaking of Christ--is nothing other than the interpretation of his prayer: the entire person of Jesus is contained in his prayer." The spiritual Christology subsequently developed by Ratzinger is one of communio. Indeed, it is one of theosis. Through a personal and ecclesial participation in the prayer of Jesus, exercised in purity of heart, and consummated in the eucharistic celebration, one comes into communion with Jesus Christ and all the members of his Body, so that eventually one can say truly, "It is no longer I who live, but Christ who lives in me" (Gal 2:20).