A moderately successful effort to address an inherently amorphous topic. Pipes (The Rushdie Affair, 1990, etc.) enters a shadowy world by distinguishing between (real) conspiracies and (imaginary) conspiracy theories. Applying this distinction requires subjective judgment, but on the whole he maintains a reasonable perspective. ``Conspiracism,'' the most virulent belief in a conspiracy, dates back to the First Crusade and reached its apex in the Soviet Union and Nazi Germany. While the British and American governments have been prime suspects in recent centuries, historically there has been amazingly little variation in the focus of conspiracists: Based on an apparently unwritten rule that the seriousness of the threat is inversely related to plausibility, Jews and various secret societies are the favorite culprits. The former have deviously hidden their intentions by posing as the persecuted, and groups as innocuous as the Freemasons and as imaginary as the Rosicrucians have dominated the world in ways that can be grasped only by the truly paranoid mind. The delusions of Hitler and Stalin moved conspiracism beyond comedy and into tragedy, but Pipes argues that these horrors have lessened its appeal and that conspiracy theories have been on the wane since the end of WW II. Oddly, while Pipes (a contributor to Commentary, the Weekly Standard, and other magazines) maintains that conspiracism is ``ambidextrous'' rather than a left- or right-wing affair, he nevertheless includes a chapter devoted to demonstrating that conspiracism of the left is now more dangerous than that of the right. This political sojourn provides insight into his more questionable judgments (e.g., downplaying the conspiracist element of American anticommunism and the popular appeal of the contemporary radical right) but adds little to a somewhat repetitive work. To be fair, however, Pipes does provide a solid sketch of a difficult and intriguing topic without indulging in sensationalism. Of course, debunking conspiracy theories might just be a way to deflect suspicion . . .