The System of Liberty: Themes in the History of Classical Liberalism, by George H. Smith, Cambridge University Press/Cato Institute, 225 pages, $29.99.

For centuries, brilliant political philosophers have taken on their ideological opponents by proving that their foes' beliefs logically imply anarchism. This was long considered a self-evident reductio ad absurdum that falsifies a political claim: If you can't defend the state, you must be wrong.

But maybe they were all correct. Maybe the state really can't be justified.

George H. Smith is an independent scholar who for many decades has lectured and written about the history of classical liberal and libertarian ideas. The System of Liberty is his first extended take on this history to be published by a high-level academic press—a tribute both to Smith's dogged scholarship and to the rise in the respectability of the libertarian tradition he explains and espouses. The book is more collection of essays than unified history, exploring, as the subtitle promises, various "themes in the history of classical liberalism." Without rigorously drawing its borders, Smith defines classical liberalism as an outlook that sees individual freedom as the highest political value. By Smith's account it first cohered in the 17th century, though unrefined elements of it can be found in older Greek and Catholic traditions.

His book touches on, among other things, the 19th century British "voluntaryists" who argued for a rigorous separation of school and state ("the State could not consistently assume the support and control of education," one of them wrote, "without assuming the support and control of both the pulpit and the press"); the key role of liberty of conscience, the true core inalienable right, in the classical liberal tradition; the real risk of imprisonment that liberals used to face; and the classical liberal belief that the only sure way to ensure the public good was to keep government restricted to protection of individual rights, thus melding utilitarian and rights-based approaches to political philosophy.

The best chapters reach bravura levels of daredevil intellectual play. "The Radical Edge of Liberalism," for example, is a close-reading ideological annotation of the Declaration of Independence. It manages to concisely and convincingly sum up centuries' worth of explanations of how and why the Declaration embodies and apotheosizes the Lockean liberal tradition, while explaining why Jefferson did not mention "property" and making the case that tyrants rather than resistors are the true rebels against the properly constituted authority that makes social life possible.

Sometimes the book falters: There are chapters that feel less like unified explorations of themes and more like info or analysis dumps. Yet even then, the information and analysis are always interesting.

The book's most valuable section is Smith's extended discussion of what he calls "the anarchy game"—the game of refuting your philosophical opponents by insisting their political philosophy necessarily implies anarchism.

Robert Filmer, the 17th-century advocate of monarchical absolutism, played the anarchy game against liberals who anticipated John Locke's argument that government should be based on consent. If governments derive their just powers from consent of the governed, Filmer argued, why would anyone give such consent? Where and when did people agree to this government? And if the world is not to be ruled by a single king, implying that smaller communities have the right to form separate sovereignties, why does this principle not apply all the way down to individual families? Filmer wasn't defending anarchism: He was mocking those who believed governments derived their rights from consent by proving that this path led to anarchy.

Other people suspicious of Lockean liberalism—including Edmund Burke, whose Vindication of Natural Society (originally published anonymously) seemed to defend anarchism but by Smith's telling was a parody meant to reduce it to an absurdity—have used FIlmerian arguments to question liberalism's ability to justify any government at all. In 1689, Locke turned around and played the anarchy game against Filmer: Even if he could prove that God granted sovereign power to someone, there would be no way to rigorously prove that any given actual government on Earth holds that God-given power—"tis necessary that [people] know not only that there is a Power somewhere in the World, but the Person who by Right is vested with this Power over them," Locke wrote in his First Treatise on Government.

Jeremy Bentham, for his part, admitted that the idea underlying his philosophy of utilitarianism "when considered rigorously…may appear fictitious," but he decided that we just had to accept that fiction, because without it, "all political reasoning is at a stand." If we didn't accept a state based on maximizing utility, even if we know there's really no way to do that, how could we accept a state at all?

Many political thinkers of all stripes considered the French Revolution a living bad example of where all this individual rights stuff can get a society; Smith argues that this helped blunt the radical edge of liberalism and helped prompt the 19th-century shift away from rights-based arguments even among liberals. But while you might not like where rights can lead, Smith argues at length that "rights" are not something any political philosopher can dismiss. Indeed, a belief in government requires a belief that the governing authority has the right to govern. Smith has no patience with defenders of the state who act as if only believers in self-sovereignty bear the burden of justifying the rights they claim. In the eyes of all 17th- and 18th-century political philosophers, he writes, "to reject all appeals to rights would have meant the destruction of political philosophy as a coherent discipline."

Classical liberalism began in freedom of conscience and took the implications of that for freedom writ large to fresh and exciting places. Its advocates deserve credit for a world that is largely free of slavery, somewhat free of conscription, and increasingly inclined to respect freedom of speech and the press. Today's libertarians fight to extend the right to be free of coercion still further.

How far? Absolutism, consent, utility: All these excuses for a state seem to fall apart, in the eyes of some of our brightest political thinkers. This might tell us something.