 As noted above, Dworkin’s arguments against positivism depend upon claims about the phenomenology of adjudication and about the constraints imposed on jurisprudence by legal disagreement. Mark Greenberg’s recent work takes as its starting point many of Dworkin’s claims, but his conclusions are in several ways more radical (see Greenberg 2004 and 2014). Greenberg’s central argument against positivism is methodological: no one, he suggests, would deny that the content of the law depends at least in part upon social facts. However, the question of which facts—the semantic content or intended effect of legislation, for example—cannot be answered by reference to further of the same: “law practices…cannot determine their own relevance” (2004: 185). Appeal must therefore be made to other kinds of considerations—for Greenberg, considerations about the moral import of our social practices. It is positivism’s error to suggest that law could be practice-based all the way down. That the content of law depends upon social sources, however, is a truth borne out by law in general, as opposed to being established within local legal practices. There is a categorical difference between the validity of the sources thesis—a truth about law as a kind of social practice—and the claim that in the UK, for example, statute renders it is illegal to drive above 70 miles an hour on the motorway. In this way the former explains the latter without circularity, and without the need for appeal to morality.