Libertarians like to think of themselves as defenders of liberty. For example, Friedrich A. von Hayek sees his work as restating an ideal of liberty for "We are concerned with that condition of men in which coercion of some by others is reduced as much as possible in society" (1960, p. 11). Similarly, John Hospers believes that libertarianism is "a philosophy of personal liberty—the liberty of each person to live according to his own choices, provided that he does not attempt to coerce others and thus prevent them from living according to their choices" (1971, p.5). And Robert Nozick (1974) claims that, if a conception of justice goes beyond libertarian "side-constraints," it cannot avoid the prospect of continually interfering with people's lives.

Libertarians have interpreted their ideal of liberty in two basically different ways. Some, following Herbert Spencer (1820–1903), have taken a right to liberty as basic and have derived all other...