 Wright identifies six “conceptual constraints” that diverse Marxist approaches to class—including his own—typically respect (1985: 26–37). First, that the class structure of a society is the “basic” determinant (1985: 28) of the limits of possible variation in class formations, class consciousness, and class struggle. Second, that class structures constitute the central organising principle of societies, shaping the possible variations of “the state, ethnic relations, gender relations, etc.”, and offering the best way of identifying historical epochs (1985: 31). Third, that the concept of class is a relational one, classes are defined within social relations, and especially by their relation to other classes (to be a feudal serf, for instance, is to stand in a certain relation to a feudal lord). Fourth, that the social relations which define classes are intrinsically antagonistic; that is, classes have conflicting interests, between which compromise or accommodation—but not harmony—is possible. Fifth, that the objective basis of those antagonistic relations is exploitation (Marxists do not, for instance, merely claim that lords are rich and serfs are poor, but insist rather that the former are rich because they appropriate a surplus produced by the latter). Sixth, and finally, that the fundamental basis of exploitation is located in the social organisation of production, notwithstanding disagreements about how to locate classes within relations of production (whether, for instance, ideology, property, control, or something else, are crucial). The last four of these constraints can be said to elaborate the structural properties of the Marxist concept of class.