In an article on Max Horkheimer entitled ‘Critical Theory and Political Economy’, Moishe Postone and Barbara Brick argue that:   In Marx’s mature theory, the notion that labor constitutes the social world and is the source of all wealth refers to capitalist or modern society alone, and not to society in general. Moreover, his analysis does not refer to labor as it is generally and transhistorically conceived: a goal directed social activity that mediates between humans and nature, transforming material in a determinate manner. Rather Marx analyzes a peculiar role that labor purportedly plays in capitalist society alone: it mediates a new form of social interdependence… that is abstract, quasi-objective, and historically dynamic. In other words, labor in capitalism constitutes a historically specific form of social mediation that is the ultimate social ground of the basic features of modernity. (Postone and Brick 1993, pp. 247–8)