Eucharist
John 6:48-58
I am the bread of life... Except you eat the flesh of the Son of man, and drink his blood, you shall not have life in you... For my flesh is meat indeed: and my blood is drink indeed.
Context of the passage
Spoken after the multiplication of loaves in the synagogue at Capharnaum, this is Christ's longest discourse on the Eucharist, given before its institution.
Catholic reading
Jesus speaks with such realism that many disciples leave him (v.66), yet he does not soften his words, confirming that he means his flesh and blood literally, prefiguring the Real Presence.
Common objection
Protestants often argue Jesus is speaking symbolically, as in John 15's 'I am the vine.'
Response
Unlike other metaphors, this saying caused scandal and desertion; if symbolic, Jesus would have clarified rather than let disciples leave over a misunderstanding. The Greek 'trogo' (to gnaw/chew) intensifies the literal sense.
The Church Fathers
“They abstain from the Eucharist... because they do not confess that the Eucharist is the flesh of our Savior Jesus Christ.”