 It is beyond doubt that moral and political considerations bear on legal philosophy. As Finnis says, the reasons we have for establishing, maintaining or reforming law include moral reasons, and these reasons therefore shape our legal concepts (1980 [2011: 266–273] and 1996: 204). But which concepts? If one accepts, as Finnis does, that the existence and content of law can be identified without recourse to moral argument, and that “human law is artefact and artifice; and not a conclusion from moral premises” (1996: 205), it becomes hard to see how the natural law theory he develops rivals rather than accommodates the truth of legal positivism (see Gardner 2001, 225–227). This vitiates also Lon Fuller’s criticisms of Hart (Fuller 1958 and 1964). Fuller has two main points. First, he thinks that it isn’t enough for a legal system to rest on customary social rules, since law could not guide behavior without also being at least minimally clear, consistent, public, prospective and so on—that is, without exhibiting to some degree those virtues collectively called “the rule of law”. It suffices to note that this is consistent with law being source-based. Even if moral properties were identical with, or supervened upon, these rule-of-law properties, they do so in virtue of their rule-like character. Whatever virtues inhere in or follow from clear, consistent, prospective, and open practices can be found not only in law but in all other social practices with those features, including custom and positive morality. And such virtues, if they exist, are minor: there is little, if anything, to be said in favor of a clear, consistent, prospective, public and impartially administered system of racial segregation, for example. Fuller’s second worry is that if law is a matter of fact, then we are without an explanation of the duty to obey. He asks how “an amoral datum called law could have the peculiar quality of creating an obligation to obey it” (Fuller 1958: 656). One possibility he neglects is that it doesn’t. But even if Fuller is right in his unargued assumption, the “peculiar quality” whose existence he doubts is a familiar feature of many practices. Compare promises: whether a society has a practice of promising, and what someone has promised to do, are matters of social fact. Yet promising creates moral obligations of performance or compensation. An “amoral datum” may indeed figure, together with other premises, in a sound argument to moral conclusions.