William Graham Sumner (October 30, 1840 – April 12, 1910) was a classical liberal (now often called "libertarian") American social scientist. He taught social sciences at Yale, where he held the nation's first professorship in sociology. He was one of the most influential teachers at Yale or any major schools. Sumner was a polymath with numerous books and essays on American history, economic history, political theory, sociology, and anthropology. He introduced the term "ethnocentrism" to identify the roots of imperialism, which he strongly opposed. He was a spokesman against imperialism and in favor of the "forgotten man" of the middle class, a term he coined. He had a long-term influence on conservatism in the United States.