Steve Prothero is the kind of professor who makes you want to go back to college. During an hour lecture of his Boston University course “Death and Immortality,” 200 students sat rapt last week as his train of thought led him from the Docetics (early Christians who believed that Jesus was all-God, not flesh), to reincarnation, to Disney World, to Hindu cremation rituals, to Plato’s account of Socrates’ trial (the day’s assigned reading), to “Beauty and the Beast,” to a hypothetical suicidal bunny, to a discussion of the merits of exile versus death for a man such as Socrates. To describe Prothero as “quick-witted” or his interests as “interdisciplinary” wouldn’t quite do him justice. Prothero is a world-religions scholar with the soul of a late-night television comic.