I understand there is a diversity of opinion in Catholicism on what is metaphor and what is concrete reality in John 6. However, to the best of my knowledge, there is no authoritative position of the RCC on this passage. Not such as could be claimed infallible. This leaves the poor Protestant floundering to find any way to accurately represent the official teaching of the RCC denomination on this issue.
Absent such authority, we are left to rummage through our encounters with various commentators, blogs, and FR debatists to sort out the full tapestry of John 6 as Catholics understand it. One thing I can tell you from years of these debates is this, when pressed to explain why transubstantiation is essential to understanding this passage, I have never seen anyone produce workable evidence to that effect.
Put another way, the passage can be fully understood without special pleading for anything beyond an ordinary metaphor. What you need for a metaphor is two things. Something you want to represent, and a different thing you use to represent it. Juliet is lovely as a summer day. Indirect metaphor. Jesus is the door. Direct metaphor. But if the thing is itself both the thing to represent and the thing represented, it no longer qualifies as a metaphor. Basic Aristotelian logic. Something cannot be both A and Not A at the same time in the same way.
Therefore, attempting to reconcile medieval theories of substance and accidence with Jesus’ teaching in John 6 is doomed to failure. The Scriptural account uses two categories, physical and spiritual , to teach the meaning of the body and the blood of Christ. Aquinas invents a new category, real but not assignable to strictly physical or spiritual but not really a hybrid of the two either. I fear it is the sort of thing no one could ever accurately represent, even with the most sincere effort.
Most importantly, as I said, the scriptural message does not need the excess baggage to make sense on its own. Occams Razor, right? The least complex explanation that accounts for all the facts is the one most likely to be correct, and that is simply this, that Jesus’ listeners were hung up on how Jesus would feed their bellies, when what they should have been worrying about was coming to Jesus in faith to meet the deep needs of their starving, lost souls.
Peace,
SR
Heck, it leaves the Catholic floundering to support their own doctrinal claims.
The overwhelming majority of these relate to believing in Jesus.
So, should we understand Jesus was placing emphasis on belief in Him as a requirement for salvation or, a very limited exchanged between unbelieving Jews who confused His message of belief and tried to think He was saying they had to eat His flesh and blood?
They wouldn't be the first to misunderstand Him. Nicodemus did not fully understand Jesus' message of being born again.