Extraordinary Popular Delusions and the Madness of Crowds is a book about the history of popular folly by Charles Mackay. The book chronicles its targets in three parts: “National Delusions,” “Peculiar Follies,” and “Philosophical Delusions.” It attempts to educate the reader as to why intelligent people do amazingly stupid things when caught up in speculative endeavors. It explores how easily we can be misled and how illogically we can think when popular opinion influences us.
Mackay’s central theme in the book is that the tendency of humans to develop a herd mentality which leads individuals in the herd to act and react to various stimuli.