One of the main challenges faced by realists in political philosophy is that of offering an account of authority that is genuinely normative and yet does not consist of a moralistic application of general, abstract ethical principles to the practice of politics. Political moralists typically start by devising a conception of justice based on their pre-political moral commitments; authority would then be legitimate only if political power is exercised in accordance with justice. As an alternative to that dominant approach I (...) put forward the idea that upturning the relationship between justice and legitimacy affords a normative notion of authority that does not depend on a pre-political account of morality, and thus avoids some serious problems faced by mainstream theories of justice. I then argue that the appropriate purpose of justice is simply to specify the implementation of an independently grounded conception of legitimacy, which in turn rests on a context- and practice-sensitive understanding of the purpose of political power. (shrink)