Abstract

Joseph Raz’s _Argument from Authority_ is one of the most famous defences of exclusive positivism in jurisprudence, the position that the existence and content of the law in a society is a wholly social fact, which can be established without the need to engage in moral analysis. According to Raz’s argument, legal systems are _de facto_ practical authorities that, like all _de facto_ authorities, must claim _legitimate_ authority, which itself entails that they must be _capable_ of being an authority. Further, once we properly understand what constitutes practical authority, as captured by Raz’s _service conception_, we realise that the directives of any authority (including the law) must be wholly identifiable without recourse to moral analysis. While the argument has previously been criticised on the grounds that the law does not claim legitimate authority, and further that the service conception of authority itself is inadequate, we argue here that the argument is actually in a worse position than these concerns recognise, for it relies upon the mistaken principle that a sincere belief or claim that _p_ guarantees _p_’s conceptual possibility.