American legal and political philosopher; for nearly half a century the most consequential English-language philosopher of law and one of the major liberal political philosophers of his generation. Dworkin held chairs at Yale, Oxford (succeeding H.L.A. Hart as Professor of Jurisprudence), University College London, and NYU, and wrote essays for the New York Review of Books with a regularity and influence unusual for an academic philosopher of his depth.
His earliest sustained project was the dismantling of legal positivism — the dominant 20th-century theory of law associated with Hart — which held that law is a system of rules whose validity depends on their pedigree (enactment, recognition) rather than their moral content. Dworkin argued in a series of essays collected as Taking Rights Seriously (1977) that this picture cannot account for the role of principles in legal reasoning, particularly in hard cases where the rules run out and judges decide on the basis of weighty general considerations (no person shall profit from his own wrong; due process; equal concern and respect). His mature theory, developed in Law's Empire (1986), framed law as an interpretive practice — judges as Herculean readers attempting to put the legal materials of their tradition in their morally best light — and made the case that there are right answers to legal questions even when reasonable lawyers disagree.
His political philosophy ran in parallel. Sovereign Virtue (2000) offered the most worked-out post-Rawlsian theory of distributive justice — equality of resources, with its hypothetical insurance markets and famous distinction between option-luck and brute-luck inequalities — and argued that liberal equality, properly understood, requires a substantial welfare state without collapsing into the leveling that conservative critics fear. Justice for Hedgehogs (2011) made his concluding case that the various values of ethical and political life — liberty, equality, democracy, dignity — form a single integrated whole rather than the tragic pluralism of competing goods that Isaiah Berlin had defended. The hedgehog of the title (from Berlin's essay) "knows one big thing": for Dworkin, that thing was the unity of value. Across forty years his work was the most sustained argument that the law and the moral life it serves are intelligible, principled, and demanding — and that the project of liberal political philosophy is the patient elaboration of what equal concern and respect actually requires.