Robert Nozick in the context of "Phi Beta Kappa"

In the United States, libertarianism is a political philosophy promoting individual liberty. Libertarianism has been described as laissez-faire on economic issues while supporting civil liberties and personal freedom. The movement is often associated with a foreign policy of non-interventionism. Broadly, there are four principal traditions within libertarianism, namely the libertarianism that developed in the mid-20th century out of the revival tradition of classical liberalism in the United States after liberalism associated with the New Deal; the libertarianism developed in the 1950s by anarcho-capitalist author Murray Rothbard, who based it on the anti-New Deal Old Right and 19th-century libertarianism and American individualist anarchists such as Benjamin Tucker and Lysander Spooner while rejecting the labor theory of value in favor of Austrian School economics and the subjective theory of value; the libertarianism developed in the 1970s by Robert Nozick and founded in American and European classical liberal traditions; and the libertarianism associated with the Libertarian Party, which was founded in 1971, including politicians such as David Nolan and Ron Paul.

The right-libertarianism associated with people such as Murray Rothbard and Robert Nozick, whose book Anarchy, State, and Utopia received significant attention in academia according to David Lewis Schaefer, is the dominant form of libertarianism in the United States, compared to that of left-libertarianism. The latter is associated with the left-wing of the modern libertarian movement and more recently to the political positions associated with academic philosophers Hillel Steiner, Philippe Van Parijs and Peter Vallentyne that combine self-ownership with an egalitarian approach to natural resources; it is also related to anti-capitalist, free-market anarchist strands such as left-wing market anarchism, referred to as market-oriented left-libertarianism to distinguish itself from other forms of libertarianism.

Anarchy, State, and Utopia is a 1974 book by the American political philosopher Robert Nozick. It won the 1975 US National Book Award in category Philosophy and Religion, has been translated into 11 languages, and was named one of the "100 most influential books since the war" (1945–1995) by the UK Times Literary Supplement.

In opposition to A Theory of Justice (1971) by John Rawls, and in debate with Michael Walzer, Nozick argues in favor of a minimal state, "limited to the narrow functions of protection against force, theft, fraud, enforcement of contracts, and so on." When a state takes on more responsibilities than these, Nozick argues, rights will be violated. To support the idea of the minimal state, Nozick presents an argument that illustrates how the minimalist state arises naturally from a Lockean state of nature and how any expansion of state power past this minimalist threshold is unjustified.

A night-watchman state, also referred to as a minimal state or minarchy, whose proponents are known as minarchists, is a model of a state that is limited and minimal, whose functions depend on libertarian theory. Right-libertarians support it only as an enforcer of the non-aggression principle by providing citizens with the military, the police, and courts, thereby protecting them from aggression, theft, breach of contract, fraud, and enforcing property laws.

In the United States, this form of government is mainly associated with libertarian and objectivist political philosophy. In other countries, minarchism is also advocated by some non-anarchist libertarian socialists and other left-libertarians. A night-watchman state has also been popularized by Robert Nozick in Anarchy, State, and Utopia (1974). The United Kingdom in the 19th century has been described by historian Charles Townshend as a standard-bearer for this form of government.

Philosophical Explanations is a 1981 metaphysical, epistemological, and ethical treatise by the philosopher Robert Nozick.

The book received positive reviews. Commentators have compared Philosophical Explanations to the philosopher Richard Rorty's Philosophy and the Mirror of Nature (1979) and praised it for Nozick's discussions of the fundamental questions of philosophy and of topics such as epistemology and ethics, and welcomed it as a convincing response to charges that American academic philosophy is overly concerned with technical issues. Nozick's discussions of knowledge and skepticism have received much critical attention.

Invariances is a 2001 book by American philosopher Robert Nozick, his last book before his death in 2002.