The short answer to the question Cullen Murphy asks in “Are We Rome?” (Houghton Mifflin, 262 pages, $24) is no. “Press it too far,” Mr. Murphy himself confesses near the end of his pithy, provocative book, “or invoke it too literally, and the Rome-and-America analogy breaks down in strategic places.” Still, it is no surprise that we are still looking to Rome for omens of our national destiny. The Founding Fathers started the tradition, frequently imagining the new American Republic in terms of the vigilant, virtuous Roman Republic. In the Federalist Papers, Alexander Hamilton argued for a “vigorous” executive branch by appealing to the Roman practice of naming a temporary dictator: “Every man the least conversant in Roman story,” he wrote, “knows how often that republic was obliged to take refuge in the absolute power of a single man.” In another installment, he warned against an “extensive” standing army, reminding his readers that “the liberties of Rome proved the final victim to her military triumphs.”

This kind of allusion came as naturally as breathing to Hamilton, writing at a time when every educated man knew his Livy as well as he knew his Bible. You only have to visit Washington, D.C., with its monumental imitations of Roman temples, to see how strongly Rome continued to grip the American imagination of power. “The Jefferson Memorial,” Mr. Murphy reminds us, “is a diminutive version of the Pantheon.” But in the 20th century, and especially after World War II, Rome offered a different, less comforting reflection. Just as the Roman Republic gave way, after centuries of pious integrity, to the grasping, doomed Empire, so the United States, in the American Century, seemed to be evolving into something more splendid and less trustworthy. It was W.H. Auden — an English poet who became an American professor, much as Greek poets used to set up as tutors in Rome — who best captured this new sense of American Empire, in poems like “The Fall of Rome”:

Fantastic grow the evening gowns;
Agents of the Fisc pursue
Absconding tax-defaulters through
The sewers of provincial towns …
Caesar’s double-bed is warm
As an unimportant clerk
Writes I DO NOT LIKE MY WORK
On a pink official form.

Today, Americans are far less “conversant in Roman story” than the audience Hamilton addressed. That is why Mr. Murphy, a longtime editor at the Atlantic Monthly who now works for Vanity Fair, has written this primer, which combines colorful episodes from Roman history with somber deductions about American history. Writing in a post-September 11, 2001, moment when the allure and pitfalls of the imperial role have never seemed stronger, Mr. Murphy asks the inescapable question: “Will historians someday have to reason to ask, Did America really fall?”

“Are We Rome?” is an essay in polemic, not scholarship, and Mr. Murphy does not set out to analyze the deep structural forces of Roman or American history. Instead, he makes a tour of contemporary American politics, and speculates about Roman parallels to very upto-the-minute problems. In many ways, Mr. Murphy’s argument is less about America in general than about the Bush administration in particular. Thus he worries about the transfer of government functions to private contractors like Halliburton, seeing an analogy to the Roman system of patronage. Provocatively, he compares the current debate over Latin American immigration to the Empire’s failure to secure its borders against “barbarians”: “Rome was no stranger to dislocations caused by worldwide market forces, or to the riotous and unpredictable interplay of ethnicities and cultures and religions.”

Above all, Mr. Murphy suggests that the American invasion of Iraq was driven by the same kind of imperial hubris that led Rome to disaster. “The Parthians,” he writes, “were not the equal of the Romans in any strict military sense, but as horsemen in mobile warfare they were superior. … Crassus and his forces were teased and bedeviled by the canny Parthians, and drawn deeper and deeper into an alien environment.” Mr. Murphy doesn’t need to come out and say that Iraq is our Parthia; it’s enough to point out the Parthians, too, lived on the Euphrates.

That sort of suggestive, unfleshed analogy, in fact, is both the strength and the weakness of “Are We Rome?” Mr. Murphy has a gift for striking juxtapositions, whereby America seems to hover above the outlines of Rome like an image in a stereoscope. Hadrian’s Wall, built to secure the Empire’s northern border in Scotland, becomes a forerunner of America’s border fence along the Rio Grande. The standardized architecture of Roman military camps, identical from Britain to Syria, reminds Mr. Murphy of Bagram Air Force base, a simulacrum of an American town built in the middle of Afghanistan. In one passage, Mr. Murphy jumbles up quotations from the e-mails of American soldiers with scraps of writing unearthed from the Roman army camp at Vindolanda. Two thousand years, he shows, have not made much difference in a soldier’s daily life. Imaginative echoes like these make “Are We Rome?” a book to muse over.

Yet these surface similarities can obscure the deeper divergences between Rome and America. In almost every way you can name — socially, politically, religiously, technologically — the two nations occupy different universes. Mr. Murphy acknowledges these differences, but because he does not go very deeply into either Roman or American history, they don’t register as strongly as the similarities he alleges. It is useful to remember that Rome began as an aristocratic oligarchy, where a small caste of patricians kept down the majority of plebeians by law and force. On several occasions, Livy records, the plebs literally seceded from the city, refusing to fight in the patricians’ wars. America, on the other hand, was democratic from the beginning, and remains deeply hostile to aristocratic pretensions. Early Rome followed an authoritarian, superstitious cult; America enjoys religious pluralism. Rome was feudal and depended on slavery; America is capitalist, and paid the highest price to rid itself of slavery. Rome never advanced beyond its impressive, yet limited, principles of engineering; America belongs to the age of technology, and transforms itself in every generation. Above all, Rome occupied the center of a world of which it was largely ignorant. Mr. Murphy suggests that Rome’s imperial self-satisfaction finds an echo in Americans’ ignorance of history, languages, and geography, and he is surely right. When you are the master of a whole continent, the need to learn about other people and places seems remote. Yet Rome’s ignorance was far more profound: It knew little of India, Asia, or Africa, and never suspected the existence of the Americas. When Rome fell, in the 5th century of the common era, it was because the eruption of the Huns from Central Asia drove the Gothic tribes westward, into collision with the Empire. Yet the Romans had no idea who the Huns were or where they came from. It was as if the world had been overrun by space aliens.

That kind of complete overturning of the known world, which lent the fall of Rome its apocalyptic character, is no longer possible; we know ourselves and each other too well. (If we encounter a comparable devastation it will be self-inflicted, though Mr. Murphy has curiously little to say about nuclear weapons.) For the same reason, America, despite its current power and primacy in world affairs, does not imagine that it is anything nearly as powerful or as central as the Roman Empire. If we are looking for an imperial analogy to America in the 21st century, the best one is probably Britain in the 19th. Like us, the British were a commercial people who sought to extend their zone of influence through a combination of persuasion and force; and like us, they always had to negotiate their position in a multipolar world. The analogy is far from perfect, but at least it gives a more realistic sense of America’s predicament than the Roman alternative.

The basic blurriness in Mr. Murphy’s argument, in fact, comes from his failure to distinguish between Rome in particular and empires in general. Most of what he describes in contemporary America as ominously Roman — arrogance, corruption, strategic overstretch — are in fact the common challenges facing any great nation. Likewise, most of his prescriptions — greater public spirit and virtue, greater modesty in dealing with the world — apply equally well to any country in the hour of its pride. That does not mean they are wrong, just that we don’t need to summon Rome’s ghost to deliver them. In fact, Mr. Murphy’s book, like all meditations on the Roman Empire, finally has only one piece of certain wisdom to impart: that all human institutions, even the best, are transitory. Or as Auden put it, in “Under Sirius”:

It is natural to hope and pious, of course, to believe
That all in the end shall be well,
But first of all, remember,
So the Sacred Books foretell,
The rotten fruit shall be shaken.

akirsch@nysun.com