 A society has a legal system only when, and to the extent that, it honors this ideal, and its law is the set of all considerations that the courts of such a society would be morally justified in applying, whether or not those considerations are determined by any source. To identify the law of a given society we must always engage in moral and political argument, for the law is whatever requirements are consistent with an interpretation of its legal practices that shows them to be best justified in light of this animating ideal. In addition to these philosophical considerations, Dworkin invokes two features of the phenomenology of judging, as he sees it. He finds deep controversy among lawyers and judges about how important cases should be decided, and he finds diversity in the considerations that they hold relevant to deciding them. The controversy suggests to him that law cannot rest on an official consensus, and the diversity suggests that there is no single social rule that validates all relevant reasons, moral and non-moral, for judicial decisions.