In this article, I elaborate a critique of social class as the concept is commonly employed in sociological analysis, that is, as the category that allegedly provides the most adequate picture of the basic social relations of modern societies. We should keep in mind that beneath such pretense of realism lie normative concerns. Thus, I argue that extra-economic and extra-mercantile mechanisms for the distribution of power and wealth, such as the division of sexes, continue to act within modern capitalism; this is similar to what happens within peripheries and areas of colonial expansion, as expressed through the category of race. In the contemporary post-colonial world, sociology must move forward to conceive of race and sex as social relations not to be confounded with objects linked to genetics and biology; rather, together with social classes, they structure power relations and exploitation. In the present text, I defend the thesis that the movement which constitutes sociology as a discipline that conceives social phenomena as independent from their connections to the natural world only comes to true fruition when it takes on the study of the social definition of the sexes 1 . Mage, v. 18, p. 209-228, 2014. A shorter version will be published as a chapter in an edited volume put together by Nadya Araujo GUIMARAES, Margaret MARUANI, Bila SORJ (French version) e Alice Rangel de Paiva ABREU, Helena HIRATA, Maria Rosa LOMBARDI (Portuguese version)