Those who read my apologetics work know my fondness for the so-old-it's-new argument from undesigned coincidences. I'm feeling too lazy right now to scare up the links to all the posts that I and Esteemed Husband have written on this subject, so I'll have to leave it to readers to Google them or use the "evidentialism" and "apologetics" tags here and at W4 to find mine. Some of my older ones have links to a series of six posts that Tim did on undesigned coincidences (in Acts). I have more written work in the pipeline on this argument--one scholarly article using probability theory and possibly a layman-level book manuscript.
As I have been filling out further a chart originally begun by my husband Tim on undesigned coincidences in the gospels, thinking about what to include in a longer manuscript, I have hesitated to include in such a book-length treatment the UC I plan to discuss in this post. The reason for my hesitation is that this particular UC involves us immediately in some intra-Christian disagreement about interpretation.
I was always taught as a Baptist (both in church and at Bible college) that Jesus' discourse on "eating his flesh" and "drinking his blood" in John 6 had nothing whatsoever to do with Communion. It was just an elaborate metaphor for believing in him with saving faith, and nothing more, period.
In part, my change from memorialist to sacramentalist on the significance of Holy Communion was occasioned by the realization that this insistence is simply interpretively insupportable. To argue that Jesus meant nothing about the Last Supper and hence Communion by the discourse in John 6 is to assert that his use of the same terminology in both places is pure coincidence. But from the sheer perspective of human communication, this must be false. There is no way in the world that Jesus just happened to speak of eating his flesh and drinking his blood in both places, but that in one place it referred purely to believing on him, without even mysteriously foreshadowing his later establishment of the rite of Communion, while in the other place it referred to taking Communion as (on the memorialist view) a purely symbolic act showing one's remembrance of his death.
It seems beyond doubt that the disciples, who must have thought the John 6 discourse very odd (some previous followers forsook Jesus altogether over it), would have remembered his words when he later spoke almost exactly the same words at the Last Supper. In the former case he stresses the importance of eating his flesh and drinking his blood. In the latter case he actually hands them bread and wine and tells them to go ahead and eat and drink, because this is his body and blood. It is extremely likely that the disciples at the Last Supper would have thought something like, "Aha, this must be telling us more about that weird stuff he was saying a couple of years ago about eating his flesh and drinking his blood." Even without any worked-out sacramental theology, they would of course have associated the two sayings of Jesus and would have taken them to be about the same thing.
Moreover, we know that Jesus often did say things that his disciples only understood later. For example, his reference to Jonah in the belly of the whale was a prophecy of his resurrection. His reference to raising up the temple after three days was likewise a reference to the resurrection. His teaching about the Comforter was probably confusing to them, though not unclear in itself, prior to the day of Pentecost.
It would be possible for a memorialist to acknowledge that the disciples would have back-solved the John 6 discourse as an allusion to Communion while retaining his memorialism. Presumably such a memorialist would say that, yes, it was about the Lord's Supper, but it was simply about the particular memorial act of obedience in the Lord's Supper.
I do not think that is satisfactory as an interpretation of John 6 either, because of the peculiar urgency and explicitness of Jesus in his discussion. Jesus insists that you have no life in you if you don't do this act, whatever it is, of eating his flesh. But memorialists don't believe anything like that about the urgency and theological importance and efficacy of taking Communion, even though of course they can be very respectful and solemn about it. (Some memorialists are even more respectful of Communion than some in allegedly sacramental denominations, but I'll say no more about that right now.)
But regardless of whether I consider that a satisfactory interpretation of John 6, it is at least not crazily, wildly implausible, as is the insistence that John 6 isn't about Communion at all at all no no no.
This leads me to the slightly wan hope that I could give this undesigned coincidence to any audience, whether memorialist or sacramentalist, and have it seen as valuable rather than as divisive. But probably not.
So I'll just give it in this post, because I think it has merit. And it is just this: It's a remarkable fact that the Gospel of John does not record the institution of the Lord's Supper. It's amazing how many years I was a Christian without realizing this. John, of all authors! John the theological, John the observant, John who tells us so much else about the night in which Jesus was betrayed, does not record the institution of the Lord's Supper. Instead, John gives a vivid account of Jesus' act of washing his disciples' feet, which is found nowhere in the synoptic gospels. On the other side, the synoptic gospels all contain an account of the institution of the Lord's Supper, including Jesus' words "this is my body" and "this is my blood" and his injunction to the disciples to eat and drink thereof, but they do not contain any parallel of the passage in John 6 in which Jesus says that you have no life in you unless you eat of the flesh of the son of man and drink his blood (vs. 53).
If John had made up the discourse in John 6, it seems undeniable that he did so as a deliberate parallel to the institution of the Lord's Supper found in the synoptics. But in that case, why did he not include the fulfillment of Christ's words? One would, in fact, almost expect him to include not only the Last Supper but some sort of allusion back to what Jesus had said earlier, tying the two passages together. But John's selection interests are different, he is not writing a piece of literary fiction but a piece of memoir-like history, and he includes the discourse but not the Institution. This is to my mind a strong indication that the discourse really occurred and that John included it because he knew that it really occurred. The discourse and the Last Supper fit together as question and answer. Why did Jesus say these strange things in John 6? Because, as was his wont, he was both stretching his audience with somewhat mysterious utterances, demanding that his followers trust him that all would be made clearer in time, and foretelling his institution of the Lord's Supper and teaching its importance in the life of the Church and the individual believer. The discourse itself answers a different kind of question: Would Jesus do something so cryptic as institute the Lord's Supper in the words he used without giving the disciples any more teaching on the matter? Of course, John himself emphasizes that Jesus did and said many things that are not recorded, many more than could be recorded, and it is entirely possible that Jesus taught the disciples more, perhaps during the forty days after his resurrection, about how they were to practice the Lord's Supper and baptism after his ascension. I consider that entirely plausible. But if we actually have teaching from Jesus about the Lord's Supper in John 6, that passage itself partly fills the apparent gap left by the brevity of his remarks on Maundy Thursday.
So the synoptic accounts of the Last Supper and the discourse in John 6 fit together in the classic way that we find in many undesigned coincidences--missing pieces supplied by each passage to fill out the whole picture, questions raised by one passage and answered in the other.
This is, like it or not, evidence of the veracity of the gospel accounts. While one will have to decide on a case-by-case basis when to include it or leave it out in any given presentation, it deserves to be examined and known, despite its apparently anti-ecumenical implications.