Christ can be no clearer in his words than this. Christ is the living manna that came down from heaven. He declares openly that His flesh is the living bread. He is the bread of life which has come down from heaven. To have eternal life, you must eat of this bread. Does the word “eat” mean “believe?” Not exactly. Does that mean that belief in Christ is synonymous with eating His body? Absolutely not. One must commune with God. This is done through the Eucharist. Just as the Holy Spirit changes your soul at baptism (surely a depraved human being cannot have any such power to change his own soul) the Holy Spirit can and does change ordinary bread and wine into the body and blood of Christ. Christ accomplished that same feat at the last supper (really the first supper). Christ did not cut off His arm and pass bits of His flesh to His fellow disciples and did not drain His blood from His severed arm into a cup and pass it around for the apostles to drink. Christ with the aid of the Holy Spirit changed ordinary bread and wine into His body and blood. The apostle participated in a living sacrifice which was later confirmed and displayed in His actual death on a cross. So we do have to believe. We must believe that we eat this “living manna” every time we receive the Eucharist.