William Graham Sumner was an American clergyman, social scientist, and neoclassical liberal. He taught social sciences at Yale University, where he held the nation's first professorship in sociology and became one of the most influential teachers at any other major school.

Neoclassical liberalism is a tradition of the liberal thought that, with the premises of John Locke's classical liberalism applied to industrialized societies, stands in opposition to the welfare state and social liberalism. In the United States, the Arizona School of liberalism, also referred to as "bleeding-heart libertarianism", adopted the term neoclassical liberal to advance certain ideas of Chicago School economist Milton Friedman within the American libertarian movement, including the school voucher system and the negative income tax.