Why do Internet, financial service, and beer commercialsdominateSuper Bowl advertising? How do political ceremoniesestablishauthority? Why does repetition characterize anthems andritualspeech? Why were circular forms favored for public festivalsduringthe French Revolution? This book answers these questionsusing asingle concept: common knowledge. Game theory shows that in order to coordinate its actions,agroup of people must form “common knowledge.” Each person wantstoparticipate only if others also participate. Members musthaveknowledge of each other, knowledge of that knowledge, knowledgeofthe knowledge of that knowledge, and so on. Michael Chweappliesthis insight, with striking erudition, to analyze a rangeofrituals across history and cultures. He shows thatpublicceremonies are powerful not simply because they transmitmeaningfrom a central source to each audience member but becausethey letaudience members know what other members know. Forinstance, peoplewatching the Super Bowl know that many others areseeing preciselywhat they see and that those people know in turnthat many othersare also watching. This creates common knowledge,and advertisersselling products that depend on consensus arewilling to pay largesums to gain access to it. Remarkably, a greatvariety of ritualsand ceremonies, such as formal inaugurations,work in much the sameway. By using a rational-choice argument to explain diverseculturalpractices, Chwe argues for a close reciprocal relationshipbetweenthe perspectives of rationality and culture. He illustrateshowgame theory can be applied to an unexpectedly broad spectrumofproblems, while showing in an admirably clear way what gametheorymight hold for scholars in the social sciences and humanitieswhoare not yet acquainted with it. In a new afterword, Chwe delves into new applications ofcommonknowledge, both in the real world and in experiments, andconsidershow generating common knowledge has become easier in thedigitalage.