Dr. James McGrath of Butler University claims that the origin of Christianity is better explained by the hypothesis that Jesus of Nazareth was an actual historical person rather than the hypothesis that Jesus was a purely mythical creature. He often cites mythicist's inability to explain how first century Jews came to believe that the messianic prophecies in the Old Testament had been fulfilled in the person of a crucified criminal if in fact there were not an actual crucified person who was believed to be the Messiah.
Conservative Christian apologists make a similar argument to defend not just the historicity of Jesus of Nazareth, but the historicity of all the events described in the gospels including the actually physical resurrection of Jesus. They claim that a literal intepretation of the gospels is necessary to adequately explain the conversion of Paul, the willingness of the first Christians to die for their believe in the resurrection, the empty tomb, and various other elements of the gospels which they claim are "facts."
These arguments came to my mind as I watched a video known as "The Banned Mormon Cartoon" which purports to describe the beliefs of the Latter Day Saints. H/T to Ken Pulliam at Why I De-Converted from Evangelical Christianity.
(I say "purports" because the cartoon was produced by an ex-Mormon Christian in order to discredit Mormonism. As such, it exaggerates and distorts many Mormon beliefs. For example, from what I can gather, it was never official LDS doctrine that Jesus had three wives or that Elohim physically had sex with Jesus' mother Mary. Nevertheless, it seems that most of the stuff in the cartoon has been believed or taught by at least some Mormons at one time or another even if it is not presently LDS doctrine.)
What is the explanation for a church based on such beliefs growing to more than twelve million members in less that two centuries? There is some evidence that upstate New York in the early nineteenth century was particularly fertile ground for innovative religious beliefs. Perhaps sociologists and psychologists could tell us something about the strength of Mormon communities today and the hold they exert upon adherents. Perhaps as one commenter on Pulliam's blog suggested, Rational Choice Theory provides the best framework to understand the phenomenon.
One place I do not think I would look for an answer is in the actual historical reality of anything that Joseph Smith believed or taught. I don't think that the origin of the Church of Jesus Christ of Latter Day saints is in any way explained by the historicity of Jesus' appearance in America shortly after his resurrection, or by Moroni burying golden plates in the fifth century A.D. which described the history of Jesus' followers in America, or by Joseph Smith actually finding those plates and translating them by sticking his head in a hat and reading them with seer stones.
By the same token, I wonder whether positing some historical reality behind the gospel stories actually adds anything to our understanding of the origins and growth of Christianity in the first two centuries. The example of Mormonism demonstrates that a religion can enjoy phenomenal growth among reasonably advanced people regardless of the plausibility of any of its historical claims. I cannot help but think that the best explanation for the origin of Christianity lies in the sociological and psychological susceptibilities of its first century adherents, not in the historicity of the things they believed.