The Long Arc of Legality breaks the current deadlock in philosophy of law between legal positivism and natural law by showing that any understanding of law as a matter of authority must account for the interaction of enacted law with fundamental principles of legality. This interaction conditions law’s content so that officials have the moral resources to answer the legal subject’s question, ‘But, how can that be law for me?’ David Dyzenhaus brings Thomas Hobbes and Hans Kelsen into a dialogue with H. L. A. Hart, showing that philosophy of law must work with the idea of legitimate authority and its basis in the social contract. He argues that the legality of international law and constitutional law are integral to the main tasks of philosophy of law, and that legal theory must attend both to the politics of legal space and to the way in which law provides us with a ‘public conscience’.