Otto Weininger was an Austrian philosopher whose provocative book Sex and Character suggested that all humans had both male and female characteristics, while also equating femininity with "Jewishness"-an idea seized on by the Nazis. In Hitler's Favorite Jew: The Enigma of Otto Weininger, Professor Allan Janik draws upon a half century of research to explore the life and work of this highly controversial figure, shedding new light on his intellectual development and beliefs, and questioning the accepted interpretation of Weininger's ideas-assertions that have fueled the fires of male chauvinism and racial bigotry for a hundred years.