John Lukacs is that rarest of political species in America, a genuine conservative. There are many politicians and voters who call themselves conservatives, just as many proudly take the name of liberals. But both of these terms have evolved so much since they first emerged, to describe the successors to the Tory and Whig parties in 19th-century British politics, that they have only the barest connection to their original meaning. In America, conservatism has always been something of a fish out of water, since the country’s entire history and spirit are ill at ease with the notion of conserving, of deliberately holding back the stream of progress. Indeed, today’s conservatives cherish the classical liberal principles – popular sovereignty, limited government, and economic freedom – for which the American and French Revolutions were fought. As Mr. Lukacs writes, “There was (and still is) so much in American ‘conservatism’ that was (and is) not conservative at all.”

For Mr. Lukacs, the eminent historian and biographer of Churchill (whose political career was a prime example of the confusion of “conservative” and “liberal” labels in the 20th century), this heritage leaves contemporary conservatives ill-equipped to defend themselves, and the country, against the real danger in modern politics: what he calls “populist nationalism.” The effort to define this threat is the plumb line that connects the disparate observations, opinions, and crotchets that make up “Democracy and Populism: Fear and Hatred” (Yale University Press, 244 pages, $25). This book belongs to the distinctive mini-genre of late reflections by senior historians, of which the last year has given us several examples (by Robert Conquest and William Pfaff, among others). Such books can be identified by their weighty theme and weary prose, and by the author’s inclination to list his opinions rather than argue them.

This is a privilege Mr. Lukacs has earned, if anyone has, but the book that results does not quite rise to the burden of its theme, which is nothing less than the decline and fall of modern civilization: “We can see – more: we ought to see – that the entire so-called Modern Age, 1500-2000 … is now at an end.” Perhaps a historian ought to be especially wary of the presentism involved in such a claim – the belief that our own time happens to be a hinge of history, and that the bustle of current events is really its epochal creak. All that Mr. Lukacs really adduces in support of his argument is his personal distaste for contemporary culture – that is, what he knows of it. For he keeps that culture, with all its undeniable flaws, at such an antiseptic distance that his criticisms of it do not have the ring of truth. It is not necessary to like one’s times in order to imaginatively understand them, but it may be necessary to look at them more unguardedly and sympathetically than Mr. Lukacs does.

Mr. Lukacs’s point of regard is that of a genuine, Burkean conservative. His values are patriotic, religious, and quasi-aristocratic, and he is equally skeptical of both the major innovations of 20th-century politics: nationalism and socialism. It is no coincidence that these were also the two names of the century’s greatest evil; a large section of “Democracy and Populism” is devoted to sketching the intellectual and political history of National Socialism, with the aim of demonstrating that Hitler was not a reactionary, as he was often called in 1930s, but a revolutionary. Even the broad term “fascism,” Mr. Lukacs argues, obscures what was genuinely modern in Hitler’s ideology – its uninhibited appeal to the people, its mobilization of popular sovereignty for conquest and violence. He insists that Nazism was not, as it is often called, an exaltation of the state, but of the people, a still more dangerous phenomenon: “For us,” Hitler said in a passage quoted by Mr. Lukacs, “the idea of the Volk is higher than the ideas of the state.”

What disturbs Mr. Lukacs about contemporary American conservatives – or, better, Republicans – is their willingness to appeal to such populism, which can never be a genuinely conserving force. The “creed” that Mr. Lukacs calls “American nationalism” is, he fears, at least potentially as violent as every other nationalism. “The same people who oppose governmental regulations, bureaucracy, further and further applications and extensions of the American welfare state, are, more than often, believers in and vocal supporters of ‘defense’ expenditures, of the army and navy and air and space programs, of more police powers, etc. – as if these were not ‘government.'” While Mr. Lukacs does not directly invoke Iraq or the war on terror, these are clearly the context for his criticism of American nationalism in general, and of President Bush in particular: “At the time of writing,” Mr. Lukacs notes, “the current president of the United States chooses to wear an enamel badge of the Stars and Stripes constantly, on the lapel of every one of his suits and other garments – demonstrating that he is an American nationalist.”

The kind of conservatism Mr. Lukacs would like to see can be deduced from his dire vision of American culture: “a roiling and mobile civilization marked by a steady increase in carnality, vulgarity, brutality.” Some of the symptoms of this “brutality” named by Mr. Lukacs are the expected ones: sexual liberation, youth culture, and popular music all come in for repeated abuse. Others are frankly idiosyncratic: Mr. Lukacs must be the only person in America troubled by the fact that “supermarkets are awash with luxuries, oranges, chocolates.” To combat this carnal abundance, he calls for a return to an idealized Victorianism: honor for men, self-sacrificing chastity for women, modesty and privacy for all. Because Mr. Lukacs is a Catholic, there is also a religious, natural-law tinge to this vision: He holds up the Catholic Church as “the last, embattled and tattered … bastion and inspiration of personal integrity, decency and, yes, of liberty and of hope.”

Mr. Lukacs offers his prophecy, and his prescription, in full recognition that neither will be popular. But it may still be worthwhile to point out that there are principled, not just hedonistic, reasons to dissent from Mr. Lukacs’s Jeremiad – reasons rooted in the liberal principles held in common by most Americans on the right and on the left. To believe that the people are the only possible source of government sovereignty; to refuse laws and customs based on any one sect’s interpretation of the divine will; to be deeply reluctant to trample on human happiness in the name of any abstraction (as Mr. Lukacs does when he peremptorily dismisses the idea of gay marriage) – this is the precious and hard-won inheritance of the modern West. The real value of “Democracy and Populism” is to remind us that even these good principles can be perverted and give rise to abominations – a warning that surely cannot be heard too often.