To the practical modern mind, the idea of divine prophecy is more ludicrous than sublime. Yet to our cultural forebears in ancient Greece and Rome, prophecy was anything but marginal; it was in fact the basic medium for recalling significant past events and expressing hopes for the future, and it offered assurance that divinities truly cared about mere mortals. Prophecy also served political ends, and it was often invoked to support or condemn an emperor's actions. In Prophets and Emperors, David Potter shows us how prophecy worked, how it could empower, and how the diverse...