What is the provenance of this distinctively Catholic conviction that Jesus is “really, truly, and substantially present” under the Eucharistic signs of bread and wine? Bishop Robert Barron would suggest that we begin with the breathtaking discourse of the Lord, found in the sixth chapter of the Gospel of John. Astounded by the miraculous multiplication of the loaves and fishes, the crowds come to Jesus, and he tells them not to search for perishable bread but rather for the bread that “endures to eternal life.” He then specifies, “I am the living bread come down from heaven…the bread that I will give is my flesh for the life of the world.” The central claim of the New Testament is that Jesus is not simply one teacher among many, one more in a long line of prophets, but rather “the word made flesh,” the incarnation of the divine word which made and sustains the world. At the consecration at every Mass, the priest takes bread and wine and pronounces over them, not his own words, but Christ’s. He acts not in his own person but in persona Christi, and hence he affects the transformation that Catholics call “transubstantiation,” the changing of the bread and wine into the body and blood of Christ. And this is why, in the presence of those transformed elements, the only proper action is to fall down in worship.