Like his English contemporary Herbert Spencer, the American sociologist William Graham Sumner (1840–1910) vigorously developed and defended the theory of social Darwinism. According to this theory, individual humans are locked in a competition for survival—a life-or-death competition that the strong will win if nature is allowed to take its course. Spencer’s and Sumner’s adaptations of Darwin’s theory of evolution (or, more accurately, natural selection) to human society thus provided some of the first important statements of neoclassical liberalism. As the following excerpts from Sumner’s What Social Classes Owe to Each Other indicate, the social Darwinists believed that individuals should be left alone to compete, to succeed or to fail in life with no expectation of help from government or society.