Robert Nozick (; November 16, 1938 – January 23, 2002) was an American philosopher. He held the Joseph Pellegrino University Professorship at Harvard University, and was president of the American Philosophical Association. He is best known for his book Anarchy, State, and Utopia (1974), a libertarian answer to John Rawls' A Theory of Justice (1971), in which Nozick proposes his minimal state as the only justifiable form of government. His later work, Philosophical Explanations (1981), advanced notable epistemological claims, namely his counterfactual theory of knowledge. It won the Phi Beta Kappa Society's Ralph Waldo Emerson Award the following year.
Nozick's other work involved ethics, decision theory, philosophy of mind, metaphysics and epistemology. His final work before his death, Invariances (2001), introduced his theory of evolutionary cosmology, by which he argues invariances, and hence objectivity itself, emerged through evolution across possible worlds.
