But of course the context is very different, and in the case of "this is my body" there is an elaboration in John 6. The context of "I am the door" and "I am the vine" is consistent with the metaphorical speech. The context of the Last Supper and John 6 is not consistent:
- Actual meal is taking place at the Last Supper.
- References to actual food of the Miracle of the loaves and fishes and of the manna are made in John 6.
- The underlying theme of the Paschal Lamb is reference to real sacrifice.
- The Passion of the Cross was not symbolic or metaphorical.
- There is a commandment to "do it"; there is no commandment to do anything about doors or vines.
- If "Real food indeed" were somehow meant symbolically, the discourse would not be a "hard teaching" prompting disciples to leave.
- To eat one's flesh and drink one's blood does have a scriptural metaphorical meaning of gaining dominance (see the Encyclopedia article), clearly not intended here.
Finally, there is a direct scripture that condemns a refusal to believe in the Real Presence: "he that eateth and drinketh unworthily, eateth and drinketh judgment to himself, not discerning the body of the Lord" (1 Cor 11:29). It is therefore not a matter of agreeing to disagree as in some other aspects of the scripture open to interpretation.