Rothbard traces the intellectual origins of libertarianism back to classical liberal philosophers John Locke and Adam Smith and the American Revolution.

The core of libertarianism, writes Rothbard, is the non-aggression axiom: "that no man or group of men may aggress against the person or property of anyone else."

He argues that while this principle is almost universally applied to private individuals and institutions, the government is considered above the general moral law, and therefore does not have to abide by this axiom.

"[2] Libertarian author David Boaz writes that For a New Liberty, together with Robert Nozick's Anarchy, State, and Utopia (1974) and Ayn Rand's essays on political philosophy, "defined the 'hard-core' version of modern libertarianism, which essentially restated Spencer's law of equal freedom: Individuals have the right to do whatever they want to do, so long as they respect the equal rights of others.

"[3] British philosopher Ted Honderich writes that Rothbard's anarcho-libertarianism informed "one messianic part of the New Right".