What motivated big changes in constitutional law doctrine during the twentieth century? Rarely did important constitutional doctrine or theory change because of formal amendments to the document\u27s text, and rarer still because scholars or judges discovered new information about the Constitution\u27s original meaning. Precedent and common law reasoning were the mechanisms by which changes occurred rather than their driving force. My thesis is that most twentieth century changes in the constitutional protection of individual rights were driven by or in response to the great identity-based social movements ( IBSMs ) of the twentieth century. Race, sex, and sexual orientation were markers of social inferiority and legal exclusion throughou...