In this book we turn our attention to the Sacrament of the Eucharist, focusing on the Eucharist primarily as a sacrament that completes the initiation into Christian life and has a central position in the life of the Church. In it, there is the fullness of sharing in love where God as the eternal Father turns to man, takes charge of him through his incarnate Son and incorporates him, in the Holy Spirit, into the only community (communia) of "children and heirs of God" (cf.
Rom 8:17; Gal 4:7). However, the Eucharist also fully encompasses a grateful answer that man, incorporated in the Holy Spirit to Christ (and thus grown together into "one body"), gives "through him, with him, and in him" to the Father and, participating in the Christ's Divine Sonship, turns to the only real aim of his life.