Libertarianism represents the endgame, the final stage, of the liberal tradition in Western political philosophy. To avoid confusion, it should be noted that the word "liberal" has changed its meaning (much to the irritation of laissez-faire economists like Milton Friedman, "classic" liberals who have now become political "conservatives"). In its original sense, liberalism championed the rights of the individual against the claims of absolute monarchy. Its ur-text is Locke's "Of Civil Government" (1689), which maintained that all men possessed natural rights that no sovereign had the right to violate. Together with the apostle of economic liberty, Adam Smith, the great Enlightenment philosophers Immanuel Kant and David Hume, and later Utilitarian thinkers like John Stuart Mill and Jeremy Bentham, liberalism expressed and created the values of the most dynamic and progressive forces in society -- the rising merchant class (soon to expand into a middle class) and the nascent Industrial Revolution. Secular and rational, liberalism's towering affirmation of human rights provided the philosophical underpinnings for the Declaration of Independence. For the liberal American revolutionaries, government was a force to be checked -- a view famously expressed by Thomas Jefferson's "That government is best which governs least."

What happened to liberalism -- the word and the concept -- after the Revolution, as America moved from Jefferson's society of yeomen farmers to an industrial nation, is the subject of intense debate. According to libertarians, apologists for the ever-expanding state hijacked the word and stood it on its head: "liberals" are now apologists for statism, anti-Jeffersonians -- not real liberals at all. Today's liberals, on the other hand, argue that they are indeed acting in the tradition of Jefferson -- "using Hamiltonian (i.e. statist) means to achieve Jeffersonian ends," in the catch phrase. Jefferson's opposition to government, today's liberals argue, must be understood in its historical context, in the days when absolute tyranny was still a danger. The danger to liberty is no longer posed by government, but by capitalism run amok, as in the Gilded Age excesses that led to the Progressive Era (about which neither Boaz nor Murray have anything to say) or today's ruthless corporate downsizing. If Jefferson were alive, liberals argue, he would support our current mixed-economy welfare state.

The debate over libertarianism's relationship to liberalism is, at bottom, a debate about two kinds of liberty: positive and negative. Positive liberty is the freedom to do something; negative liberty is freedom from something. As the extreme defenders of negative liberty, libertarians make their stand on rights: Give us freedom from coercion, they argue, and we'll figure out what to do with it.

Is the libertarian position the only logical consequence of liberalism? Not necessarily. As Stephen Holmes argues in "Passions and Constraint" (1995), the liberal tradition, contrary to libertarian claims, is eminently compatible with state intervention and redistributive policies -- with positive liberty, in other words.

Nonetheless, libertarianism's exaltation of negative liberty puts contemporary liberals in something of a psychological quandary. Most liberals by temperament are drawn, like libertarians, to negative liberty. They, too, are rights-defending secular individualists, suspicious of traditional conservatives like Edmund Burke and Russell Kirk (not to mention debased mutations like William Bennett), with their talk of community and heritage, duties and responsibility, and other exhortations to dosomething with freedom. Nor are liberals in the post-Marxist era any more coherent on the subject of capitalism: They support it, but want governmental power available to curb its excesses. They believe in redistributive policies, but are painfully aware that achieving economic equality is a chimera.

In short, in comparison to libertarians, who have a clear ideological system worked out, liberals are ditherers, wandering vaguely in a muddled middle. It is not the least virtue of libertarianism that it forces liberals to acknowledge the extent to which they subscribe to certain tenets of traditional conservatism. Confronted with the daunting individualism of the libertarians, liberals must interrogate their own faith in science and reason and the heroic individual. They must articulate something that had hitherto been obscure: the role of tradition, force and the unconscious in ordering human affairs. To reject the dazzling optimism of libertarianism is to be forced to embrace a more sober vision.