Cohen proposes that explanation in Marx’s conception of the social system is functional, by which he means roughly that the character of what is explained is determined by its effect on what explains it, so that economic relations of production profoundly affect productive forces (technology), and legal-political superstructures strongly condition economic foundations. Thus, in the latter case, in one direction a society’s legal-political superstructure stabilizes or entrenches its economic structure, but in the other direction the economic relations determine the character of the superstructure, so that in this sense the economic base is primary and the superstructure secondary. It is precisely because the superstructure strongly affects the base that the base selects that superstructure.