In this essay, Leon Suprenant points us to the centrality of the Eucharist in our lives. Transubstantiation changes the bread and wine into the Body and Blood of Christ, and so we are to let the Eucharist change us wholly—so that we are fully one with Christ and can then act in the world through and for Him. Receiving the Eucharist changes our relationship with Christ, but it should also change our relationship with the world, because through Him we are united as children of a loving Father. Suprenant shows, through a well-chosen collection of Bible passages and Church documents, that the Eucharist is indeed—as Vatican II reminds us—the “source and summit of the Christian life.”