A recent comment offered a serious response to my argument about the need for independent corroboration in order to have some degree of probability given in favour of the Gospel narratives reflecting some genuine historical events.
The point of mine being addressed was this: Whether the central character itself originated as a fabrication can only be determined through an assessment of evidence external to the narrative itself. In the absence of that “control” we have no way of knowing if there is a historical basis or not.
The critical response was this:
One problem with this field of inquiry is that by and large the evidence external to the narrative is asserted nevertheless to be part of the narrative. We have evidence outside the narrative (i.e.Mark) from John’s Gospel and from Paul. But if the “narrative” is defined as the myth of a particular movement, then anything that purports to be external to the narrative will be brought back into the narrative and thereby dismissed. Josephus, for example, insofar as anything he wrote about Jesus is original to him, presumably got his information from Christians and so he is not really an independent source. He is just repeating what some people got from the narrative. So, just as it is almost impossible for me to imagine any story whatsoever about Jesus that cannot be dismissed as mythical on the grounds that it would have some sort of application to the Christian cult and its beliefs, I also suspect that anything outside of Mark that used to validate Mark will be assumed to be a fabrication as well.
And I do think it is incumbent upon those who will say that all the supposed evidence is really the ancient constructing of mythic narratives about Jesus to say why this is happening. Why are they making up stories about some obscure Galilean who never actually lived? To say “we can imagine ways to show that every bit of the supposed evidence for Jesus is just made-up” seems to me to require an explanation of why they are making it up.
My response: read more