Extraordinary Popular Delusions and the Madness of Crowds

Extraordinary Popular Delusions and the Madness of Crowds is Charles Mackay's survey of the recurring episodes in which large numbers of people have abandoned individual judgment and been swept into shared irrationality. The book was first published in 1841, revised in 1852, and covers financial manias, false sciences, social crazes, and religious upheavals across European history.

The most famous chapters deal with three financial bubbles. The Mississippi Scheme of 1719 to 1720 describes how John Law, a Scottish financier exiled for killing a man in a duel, persuaded the French regent to let him create paper money backed by the supposed riches of French Louisiana. The resulting mania saw crowds besieging his offices, aristocrats disguising themselves as servants to gain audiences, and fortunes made and lost within hours before the whole structure collapsed. The South-Sea Bubble recounts an almost identical episode in England the same year, driven by a company whose actual trade with South America was nearly nonexistent. The Tulipomania narrates how Dutch merchants in the 1630s bid a single tulip bulb up to the price of a house and eventually accepted livestock, furniture, and land in exchange for rare varieties, before the market collapsed in 1637 and left many bankrupt.

A long section on the alchemists traces a thousand years of futile searching for the philosopher's stone and the water of life. Mackay's account is more sympathetic than scornful: he argues that three universal human griefs (the fear of death, the burden of toil, and ignorance of the future) made alchemy psychologically inevitable. Great minds believed in it not because they were foolish, but because the alternative was to accept limits no one wished to accept. The pattern repeated in astrology, fortune-telling, and the various arts of divination that Mackay catalogs alongside it.

Volume Two treats the Crusades at length as a case of mass religious delusion, examining how Peter the Hermit recruited an army of hundreds of thousands by appealing to piety, guilt, the promise of plunder, and the excitement of movement. Mackay does not deny the sincerity of individual crusaders but argues that the collective result, two centuries of bloodshed for territorial gains repeatedly lost, can only be understood as a form of mania goaded by political and religious causes operating on a population that found normal life intolerable. A chapter on Popular Follies of Great Cities then catalogues smaller-scale social contagions: slang phrases that swept through London in days, fashions in dress or manner that no one began and no one could stop.

Running through every episode is Mackay's thesis about the mechanics of collective belief: confidence, like mistrust, can be extended almost without limit; a rising price seems to justify itself; and the crowd's unanimity is taken as proof. When the reversal comes it is sudden, catastrophic, and asymmetric: easy to enter, very hard to leave. Mackay's own stated aim was instruction rather than entertainment: by seeing how often whole nations have been deceived, readers might become a little more resistant to the next delusion.