Sometimes two historical records incidentally touch on the same point in a manner that would be very unlikely if one of them were copied from the other or if both were copied from a common source. For example, one account of an event may leave out a bit of information, leaving some natural question unanswered, while a different account indirectly supplies the missing detail and, in so doing, answers that question. When this happens, the best explanation is that both records are grounded in the actual historical event; that is why the two bits fit together so well.
Forgers do not want to leave loose ends like this that might raise awkward questions; they take care to tie everything together neatly. But these are just the sort of things we would expect to find in authentic records of the same real event told by different people who knew what they were talking about.
He then goes on to give some key examples from the gospels:
1. Why does Herod Antipas ask his servants about Jesus? (Matt. 14:1-2) Answer: One of the followers of Jesus was the wife of Herod’s steward. (Luke 8:3)
2. After the transfiguration, why do the disciples tell no one? (Luke 9:36) Answer: Because Jesus specifically told them to tell no one. (Mark 9:9)
3. In the lead up to the feeding of the 5,000, why does Jesus ask Philip (a minor figure in the Gospels by any standard) where they are going to find bread to feed all of these people? Answer: Because the setting was Bethsaida (Luke 9:10), which was Philip’s home town (John 1:44).
4. In John 18:32, Pilate asks Jesus whether he is a king. What prompted that question? (Nothing earlier in the chapter indicates that this was a charge leveled against Jesus.) Answer: Though John does not record it, the Jews did make that very charge against Jesus. (Luke 23:1-2)
5. In Luke 23:1-4, Pilate asks Jesus whether he is a king, and Jesus gives an answer that is certainly not a denial and that many scholars take for a terse, idiomatic acknowledgement. Then Pilate declares that he finds him innocent. How can this puzzling fact be explained? Answer: Luke is giving only a summary of the interview. In a fuller account, we discover that Jesus told Pilate that His kingdom was not of this world. (John 18:36)
6. In Mark 14:58 and Mark 15:29, the charge is reiterated that Jesus threatened to destroy the Temple. Yet nowhere in the Synoptics do we find his saying anything about this—not even something that could plausibly be misunderstood. What lay behind the charge? Answer: In John 2:18-19 we find Jesus saying, “Destroy this Temple, and in three days I will raise it up again.”
This last example fits quite well (in linking Mark and John) with Richard Bauckham’s argument, first put clearly in his chapter ‘John for readers of Mark’ in The Gospel for All Christians. But the others suggest links in other directions, and as Tim says, the most obvious explanation is that the different accounts are all working from a single historical reality.
Another connection that has interested me for a while is that between Luke and Revelation. Uniquely in Luke’s version of the ‘Sinai Apocalypse’, Luke 21, Jesus talks of people falling by ‘the edge of the sword’ (v 24), an allusion to Jeremiah 21.7 also found in Rev 13.10, and also uniquely describes Jerusalem as being ‘trampled by the Gentiles’ (same verse), a phrase found in Rev 11.2. I look forward to reading more on this in Paul Penley’s recent monograph on Synoptic traditions in the Apocalypse.
All this suggests that the NT documents are closely related to historical events, and closely related to one another in ways we have not always appreciated. And it also suggests that modern biblical scholarship has not attended to this data sufficiently. For where do these insights come from? None other than William Paley, the famous apologist, in his 1790 Horae Paulinae, material from which was picked up and expanded by John James Blunt in 1869. You can find a full bibliography at the Library of Historical Apologetics.