A rake seduces women and murders their male relatives with impunity until the statue of one of his victims invites him to supper and drags him to hell. It sounds silly, but for two centuries it was the most-favored plot device in Western literature. Don Juan was the invention of Tirso de Molina, a Spanish monk from a family of converted Jews. Concealed in its puppet-theater plot is a Jewish joke: Don Juan exists to prove by construction that a devout Christian can be a sociopath, and by extension, that the Christian world can be ruled by sociopaths. The Enlightenment’s...