[sral]

I am certainly not an expert, but will intervene anyway since some posts may be following a wrong path.

The Jews of 30 AD certainly knew whether Jesus existed or not. The Gospels make it clear he was a renowned healer. The Jews of 55 AD certainly had a pretty good idea whether he existed or not ... unless they thought all their parents' generation had been brainwashed.

In other words, if Jesus was a fabrication, many Jews of the late 1st century would have known he was a fabrication. The Jewish Talmud has passages intended to denigrate Jesus. But it lacks the obvious strong charge it might have made: that he didn't even exist! Josephus' history has been tampered with but scholars agree, I think, that some of its references to Jesus are in the original; given his dates and experience Josephus knew whether or not Jesus existed.