Both those who argue for an entirely mythical Jesus and those who see a real life human doomsday cult leader at the root of Christianity make their cases with a lot of conviction, in fact with so much certainty that one would usually assume they must be really sure that they got it figured out. Unfortunately, again, both sides do so, and I am clearly not qualified to evaluate the Ancient Greek source material and suchlike.
For what it is worth, I lean towards the assumption that there was a human cult leader named Jesus (I understand it would then have been something like Yoshua?) at the root of Christianity, obviously in my personal opinion without any actual virgin birth, divinity, resurrection or other miracles involved. My main problem with the mythicist position is that it seems really hard to explain the content of the gospels under their hypothesis. Just to pick the three first items that pop into my mind, and of course none of these thoughts are original to me:
1. Some of the gospel authors work very hard to establish that Jesus, although coming from Nazareth, was born in Bethlehem. This is because he is supposed to be the Jewish Messiah, but apparently the Messiah was prophesied to come from Bethlehem. The tortured efforts of the authors make sense under the assumption that there really was a Jesus, but he was known to have come from Nazareth. If, however, Jesus was a mythical being, and the gospel authors set out to wholly invent a teaching allegory around him or write a novel, then they could just as well have made that character come from Bethlehem.
2. An even more blatant case of trying to make Jesus fit a prophesy about the Messiah can be found in the gospel of Matthew.
1:21 And she shall bring forth a son, and thou shalt call his name JESUS: for he shall save his people from their sins.I mean, seriously: He was called Jesus, and thus the prophecy was fulfilled that he would be called Emmanuel. Again, this makes sense if the author had to work with a real life Jesus who did not fulfil prophesies that the author really, really would have liked him to fulfil. It does not make sense if the author could just write a novel as he saw fit, because in that case he could just have called the hero Emmanuel.
1:22 Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying,
1:23 Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.
3. Both Matthew and Mark have Jesus claiming that the world would come to an end during the lifetime of the people he was preaching to. From the perspective of mythicism, this is an interesting catch-22. Usually mythicists have an interest in claiming that for all we can tell, the gospels were written a very long time after the events they purport to document. (And for all I know they may be right.) However, if that is the case, then the authors wrote them at a time when it had already been demonstrated that Jesus' prophesy about the timing of the end of the world was mistaken. Surely then if they were just freely writing whatever they saw fit they would not have put these words into his mouth?
But again the presence of such a failed prophecy in the text makes more sense under the assumption that there was a real person, and that people knew that that person had made the prophecy in question.
There are ways to argue these and other oddities away under the assumption of mythicism, but to me they feel about as much like tortured ad-hoccery as the Emmanuel verse itself. I like parsimony analyses and thus prefer the more straightforward explanation. However, I stress again that I am about as qualified to decide this for myself as in the matter of Copenhagen versus Many Worlds. Meaning: not qualified.
Anyway, the way these discussions tend to proceed in the atheoblogosphere can also be rather exasperating. Both during a recent outbreak of the controversy at Larry Moran's Sandwalk blog and in the two relevant posts published around the same time by Aron Ra the following could be observed:
First, the blogger supports the idea that Jesus was originally wholly mythical, that there was no human being at the root of Christianity. Second, commenters provide arguments for why it makes more sense to assume such a human being existed. A heated discussion ensues. Third, the blogger replies somewhat annoyed on the lines of "oh come on, even if such a human being had existed it wouldn't be the divine, miracle working, resurrected character of the bible anyway, so who cares?"
True, he wouldn't. But the discussion these bloggers opened was whether a mundane human existed upon whose name, to quote Aron Ra, a mountain of nonsense was heaped after his death. They did not, I repeat: not, open the discussion whether Jesus precisely as described in the bible existed, and for good reason, because on that question all their atheist readers are agreed anyway. And with all due respect to these otherwise excellent writers, there is a term for trying to shift the discussion from the existence of a human to the existence of miracles the moment one gets too many counter-arguments; something with goal-posts I think.
Is it so hard simply to admit that one may have overstated one's case a bit? And if, as claimed, it really doesn't matter anyway because everybody in the relevant community agrees that the miracles didn't happen, shouldn't such an admission be even easier?