In some inquiries, racism is a given, a fundamental assumption and fact that is known to shape economic and social and spatial inequalities. In such inquiries, from the empirical studies of W. E. B. Du Bois to the social thought of Patricia Williams, the world is believed to be racialized “always already”: the task of the researcher, then, is to probe the roots of racism in particular cases, and to liberate (or compensate) the people who are oppressed by its institutional manifestations. Other inquiries—guided by a methodology of rational choice—do not assume racism to be a given. For example, in mainstream economics after Gary Becker, race is a possible “factor,” one vector of a matrix, whose strength and direction of force on earnings or housing differences is to be examined in a regression equation once all other factors have been held constant. Indeed, some economists after Becker argue that racism cannot explain differences in earnings or in opportunities because if the marginal product of labor (or the bid on a house) of a person of color exceeds that of the white competition, the argument goes, then no profit-maximizing employer or seller would deny the offer of the person of color. And since all employers and households are assumed to be profit-maximizers, the color of one's skin will have no economic significance at all.