The Sacrament of the Most Holy Eucharist is, as the Church said at the Second Vatican Council, the “source and summit” of the Christian life (Lumen Gentium 11). In other words, everything we do and everything we are as Catholics comes from the Eucharist, and everything we do and everything we are as Catholics leads us back to the Eucharist. This comes from the very nature of the Sacrament, in which Jesus Christ Himself is really, truly, and substantially present.
As in all other Sacraments, in the Eucharist God uses everyday things which have meanings we can naturally understand. In the case of the Eucharist, He uses bread and wine . . . food and drink. We all know without being taught that we need food and drink in order to survive. Thus, in the Eucharist God tells us that Jesus Himself is our nourishment, without Whom we cannot survive. Our physical eyes see ordinary bread and wine; our eyes of faith see our Lord and Savior.
Our Catholic belief, that in the Eucharist Jesus Christ is really, truly, and substantially present, Body, Blood, Soul, and Divinity, comes from John’s Gospel, Chapter 6. In that chapter, called the “Bread of Life Discourse,” Jesus tells the crowd that they must eat His Flesh and drink His Blood in order to have eternal life. As it slowly dawns on the crowd that He is not speaking metaphorically, but means they must actually eat His Flesh and drink His Blood, the vast majority of them leave in disgust. But Jesus will not back down or change this teaching. Instead, He asks the Twelve if they too want to leave. Peter, speaking for the group, gives the response that animates all our devotion to the Eucharist: “Master, to whom shall we go? You have the words of eternal life.” In other words, “Lord, we may not understand what in the world you’re talking about, but we choose to place our trust in you.” Thus, at the Last Supper, when Jesus handed them bread and wine, saying “Take and eat, for this is My Body . . . take and drink, for this is My Blood,” they were able to understand what He was talking about in the Bread of Life Discourse. They knew that the Eucharist is Jesus Himself . . . not a mere symbol, not simply a remembrance, but Jesus Christ truly present.
We too place our trust in the words of Jesus, and believe that He meant what He said. This is why we offer to the Eucharist what we do not offer to any statue, or image, or even to the altar itself: worship. We believe that in the Sacrament of the Most Holy Eucharist, our God is truly present in a way He is present nowhere else in the world, and that He comes to us to nourish us in our journey from this life to eternal life.