<Ul> <Li> A critique of John Austin's theory that law is the command of the sovereign backed by sanction . </Li> <Li> A distinction between primary and secondary legal rules, where a primary rule governs conduct and a secondary rule allows the creation, alteration, or extinction of primary rules . </Li> <Li> A distinction between the internal and external points of view of law and rules, close to (and influenced by) Max Weber's distinction between the sociological and the legal perspectives of law . </Li> <Li> The idea of the rule of recognition, a social rule that differentiated between those norms that have the authority of law and those that do not . Hart viewed the rule of recognition as an evolution from Hans Kelsen's "Grundnorm", or "basic norm". </Li> <Li> A reply to Ronald Dworkin, who criticized legal positivism in general and especially Hart's account of law in Taking Rights Seriously (1977), A Matter of Principle (1985) and Law's Empire (1986). </Li> </Ul> <Li> A critique of John Austin's theory that law is the command of the sovereign backed by sanction . </Li> <Li> A distinction between primary and secondary legal rules, where a primary rule governs conduct and a secondary rule allows the creation, alteration, or extinction of primary rules . </Li> <Li> A distinction between the internal and external points of view of law and rules, close to (and influenced by) Max Weber's distinction between the sociological and the legal perspectives of law . </Li>

Who said that law is the command of the sovereign