The economist, philosopher, and sociologist William Graham Sumner was a leading defender of individualism, private property, and laissez-faire capitalism in the late nineteenth and early twentieth centuries; he was also one of the most popular professors ever to teach at Yale University. His best-known work is his 1906 study Folkways: A Study of the Sociological Importance of Usages, Manners, Customs, Mores, and Morals, the only part of a projected masterwork on "the science of society" that he was able to publish during his lifetime. He is also known as the major American "social Darwinist" of the Gilded Age. Social Darwinism is the application of the biological concepts of natural selection and survival of the fittest, central to Charles Darwin's theory of evolution, to human society. The term implies a belief that social progress depends on healthy competition, and that the elimination of inferior members of society is inevitable--ideas that...