  One way to make out the possibility of disagreement about grounds that interpretivism implies is to show that disagreement of that character obtains. Dworkin said that disagreement about the grounds of law is pervasive. Many of his critics objected that the kinds of disagreement that Dworkin seemed to have in mind can be explained in a way other than as disagreements about grounds: for example, disagreements about the social facts that constitute legal norms, or about how to apply the norms, or about how to decide cases where the norms run out (therefore how to extend the law), against a background of agreement on the grounds of law (Leiter 2003; Shapiro 2007, though not a defender of interpretivism, finds such responses unsatisfactory).