Man or Myth: the Jesus Story

There is a debate currently being waged regarding whether Jesus was a real person or simply a myth. This blogosphere debate was sparked by the publication of Bart Ehrman's newest book "Did Jesus Exist?: The Historical Argument for Jesus of Nazareth". Ehrman's thesis is that Jesus was in fact a real person (albeit one without any god-like superpowers) and not a myth, unlike Uther Pendragon, Robin Hood, or Darth Vader. However, Richard Carrier, a historian, raised a number of  critiques to Ehrman's work. Ehrman responded. Carrier reresponded. etc. etc. ad infinitum.

It is unlikely that I will read Ehrman's newest book in the near future, although I have enjoyed several of his earlier works. So I won't jump into this fray. However, this debate has raised a question that I think is worth addressing. Where is the dividing line between historical and mythical?

On the one hand, we have the pure historical position. In this case, there was a man named or referred to as Jesus that did all the non-miraculous events described in the bible. Presumably, this man was also present at the events, which were not miraculous, but became the miraculous stories with retelling. Kind of like a game of telephone. I'm separating out the miraculous events as being fictitious similar to flying a broom in the Harry Potter stories. Regardless, Ehrman does not take the position that Jesus was a god-entity, just that Jesus is based on an actual human being. 

On the other hand, we have the pure mythical position. In the case, someone(s) basically made up the person and all the associated events a la Stephen King and Roland or J.K. Rowling and Voldemort. Through a confluence of historical coincidences, these stories became "real" and we wonder where in England Hogwart's is hidden.

But what about in between these two positions. Where does the mythical become the historical and vice versa? Let's say for example that an apocalyptic preacher gave a sermon that was basically what amounted to the Sermon on the Mount. This preacher's name was Larry, but otherwise a group of people came to hear Larry speak and he essentially discussed theology as described in Matthew. If everything else in the New Testament is made up by early religious leaders, is Jesus historical or mythical?

What if Larry basically gave the sermon on the mount but another preacher/religious person was talking to a veritable multitude of people along the shore. This other preacher, named Darryl, was a bit long-winded and as people were getting ready to leave for lunch a fishing boat capsized nearby providing lots of freshly caught fish for a quick snack (don't get me started on the safety of all these people eating raw fish). Maybe some of Darryl's friend brought over some bread to go with the fish, although not that much. Instant story. So now we have two different stories about real people, Larry and Darryl, and these ultimately get attributed to their deadbeat friend, who never did get a real job other than cleaning the room of a local centurion named Bob. In this example where stories of several different people get merged into a single person, are we dealing with a historical person or a mythical person?

What if there was a kid named Harold or maybe Barry that was often babysat by a young J.K. Rowling. Harold/Barry had a best friend named Tom who was generally good natured but not the swiftest broom in the closet. Harold/Barry and Tom hung out with a neighbor named Herman, who was kind of a nerd but Harold/Barry and Tom allowed Herman to hang around, at least when school was in session and Herman could help them with their studies. If the previous scenario is true, does that make Harry Potter a historical figure? Maybe this is a stupid example, but many authors based characters on real life people.
Which gets us all the way back to the question, where is the dividing line between historical and mythical? Personally, I don't think we can answer that question in a way that is justified by logic. There are too many variables. We could come to some agreed upon definition, but ultimately this would be a moving target adjusting as cultures change, information is gained, etc.