Beginning in the 1940s, Isaac Asimov created with his Foundation series an enduring classic of science fiction. He depicted the development of inconceivably vast galactic empires, guided by the predictive powers of a complex social and behavioral science known as Psychohistory. For millennia, the universe unfolds as it should. Then, overnight, all these plans are utterly confounded by the rise of a messianic prophet called the Mule, a mutant who brings all lesser mortals under his sway, and who conquers all rival empires. Instantly, all psychohistorical bets are off.

In this instance, as in so much else, Asimov took the Mule from the pages of Edward Gibbon's Decline and Fall, and specifically the account of the Prophet Muhammad (570-632). And although Asimov was explicitly...