What is Nick’s reaction to Gatsby’s autobiographical history? Does he believe Gatsby? Why or Why not?

Chapter Four is primarily concerned with the mystery of Gatsby's background, and of the source of his wealth. Though Nick was first taken with Gatsby's seeming purity and optimism, Gatsby remains enigmatic and not entirely trustworthy. Gatsby's own account of his illustrious past seems comically exaggerated. His readiness to provide evidence to corroborate his story is itself suspect; an honest man, one imagines, would be insulted by Nick's skepticism.