The Delusions of Crowds: Why People Go Mad in Groups

God, greed, and the yen for conformity reliably override reason, according to this sweeping survey of religious and financial manias. Neurologist and historian Bernstein (A Splendid Exchange) shares vivid accounts of several centuries of sectarian crazies, from the Anabaptists who took over the German city of Münster in 1534, imposing communism and polygamy and executing dissenters, to Branch Davidian messiah David Koresh and the Islamic State. On the finance front, he recaps the South Sea bubble in 18th-century England, the 1990s tech bubble, and other stock market frenzies. Bernstein lucidly deploys neurobiology, behavioral economics, and social psychology to explain why reason fails and other instances, noting, for example, that many people will believe two obviously unequal line segments to be the same length if other people say they are. Unfortunately, his conflation of all irrational doctrine with madness makes him sound somewhat hysterical about even mainstream religious politics: the “dangerous” end-times beliefs of American evangelical conservatives could, he suggests, “incinerate a large portion of humanity” by facilitating nuclear war. The result is an entertaining and insightful analysis of delusional outbursts that occasionally goes too far. Photos. (Feb.)