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.
