How have modern democracies squared their commitment to equality with their fear that disparities in talent and intelligence might be natural, persistent, and consequential? In this wide-ranging account of American and French understandings of merit, talent, and intelligence over the past two centuries, John Carson tells the fascinating story of how two nations wrestled scientifically with human inequalities and their social and political implications.

Surveying a broad array of political tracts, philosophical treatises, scientific works, and journalistic writings, Carson...