While the theory of demand—that consumers buy more as prices fall and buy less as they rise—is decidedly uncontroversial in mainstream economics, the absence of controversy belies the theory’s contentious and complicated history. This volume provides a better understanding of the history of demand theory and its relationship to major theoretical developments in twentieth-century microeconomics. Contributors investigate demand theory as it stabilized in the first half of the twentieth century by examining the Hicks-Allen composite commodity, French mathematician Jean Ville’s contribution to consumption theory, Walrasian theories of markets with adverse selection, and the Sonnenschein-Mantel-Debreu theorem. They analyze the relationship between demand theory and both the broader program of neoclassical economics and developments within contemporary economic theory. This volume demonstrates that demand theory is more complicated than it is generally imagined to be.