Pop romanizing.

Are We Rome? The Fall of an Empire and the Fate of America, by Cullen Murphy (Houghton Mifflin, 272 pp., $24)

IN the last decade, and especially after 9/11, it has become popular once again to compare the United States to ancient Rome. The pop analogies almost always appear in the pessimistic context of an American colossus betraying its origins and ideals--and, like Rome, facing the deserved end of its empire.

Those on the left warn about America's hard imperial hand on the "Other" abroad. Meanwhile, our contemporary conservative elder Catos lament the corruption of the old, small, agrarian republic into an empire. Both predict--almost gleefully, and sometimes in apocalyptic terms--American "exhaustion," "decline," or something similar to a Roman "fall."

Of course, there are a number of similarities between the two superpowers, ancient and modern. Both were practical, inclusive societies that rapidly incorporated foreigners. They alike unexpectedly achieved global stature and influence--at first through astounding feats of arms in filling the vacuum of eroding empires (the end of the Hellenistic East in the 2nd century B.C. was perhaps analogous to the postwar breakup of the British Empire).

Soon each upstart nation won further adherents by an insidiously efficient way of doing things, based on merit rather than mere class, that offered material prosperity to millions not to be found through local indigenous cultures. Likewise, brilliant Roman and American writers have left thoughtful observations about the ironies--and pathologies--of their seemingly unstoppable societies that changed the world abroad and, in the process, their once-traditional citizenry within.

But for any valid comparison, some basic ground rules of this old game of "America as Rome" are to be followed. First, keep in mind that the idea of a monolithic "Rome" is a sort of construct--reflecting 700 years of Italian republican government, followed by another half-millennium of imperial Mediterranean rule. What "Rome," then, do we of infant nations evoke? Is Rome to be the rather small, agrarian republic trying to stop Carthage in the first Punic war? Or Edward Gibbon's 2nd-century A.D. hundred years of bliss? Or the chaos of a perennially tottering empire yet another 200 years later?

Second, recognize that Roman literature, usually written by disaffected elites, is as consistently reactionary as it is moralistic in nature. Juvenal, Livy, Petronius, Sallust, the younger Seneca, Suetonius, and Tacitus, all knee-deep in the luxury of their times, all nevertheless deplored the supposed decadence of their respective eras. They can be fine witnesses to Roman decline and the corrosive effects of luxus, but their pessimistic--and often hypocritical--genre of "things going to hell in a hand basket" needs to be weighed carefully against concomitant evidence from mute numismatics, epigraphy, and archeology that reflect a booming culture often at odds with what the cynical said about it.

For the once-great families, it might have been a seminal moment to see respected Roman matrons increasingly covered with blood and dust in the first row of the amphitheater, oohing and aahing the abs of the gladiators. But most in North Africa or Eastern Europe--who with Romanization at last had clean water and habeas corpus--could not have cared less. Petronius (Nero's own arbiter elegantiae) saw the crass nouveau-riche upstarts as proof of imperial decadence. But some of the novelist's gauche characters, like the Jewish buffoon Trimalchio and the rag-collector Echion, are more likely welcome evidence that millions by the 1st century A.D. were succeeding in a global system increasingly based on merit, not class--anathema to Petronius's old Italian upper crust.

Third, there should be an up-front recognition that common Rome/America comparisons, from Oswald Spengler's to Pat Buchanan's, are rarely meant to be laudatory. Instead, they are admonitory in nature, warning that the "bread and circuses" of the United States, too, will--and should--soon end. Key is the superficiality that both Romans and Americans were somehow malevolent, forgetting that in comparison with the alternatives of the times, most of the "Other" voted with their feet to get within the imperial borders by any means at their disposal.

Cullen Murphy (editor at large at Vanity Fair and co-author of Rubbish! The Archaeology of Garbage) does not draw extensively from the evidence of the ancient world, other than selected quotes in translation from the usual grim Roman moralists. That paucity of ancient evidence is buttressed on the modern side by a plethora of references to contemporary culture. So evocation of everything from Abu Ghraib, the Green Zone, Halliburton (but of course), and Blackwater USA to Ahmed Chalabi, Ken Lay, and the Cheneys is used to hammer home the preordained point that our selfish right-wing elites have become like Suetonius's vulgar Julio-Claudians in devouring public resources, eroding our freedoms, and ruining our name and influence abroad. But even the non-classicist will finally bristle at such simplicity, replete as it is with references to the movies Spartacus and Gladiator and the video game Rome: Total War.

The predetermined conclusions govern the presentation of evidence. Murphy perhaps tips his hand at the very beginning by reminding us of a trip by George W. Bush to Europe to consult with allies. For Murphy, it was reminiscent of a Roman emperor on a visit to the northwest provinces--"a meeting, in other words, with the leaders of allied or subsidiary nations." Yes, Europeans may voice such unhappiness with their postwar subordinate roles. But the idea that they are clients like Caesar's conquered tribes doesn't work too well in the classical sense because the autonomous EU has a larger population and economy than the U.S., and often acts collectively to thwart American ambitions and visions.

Murphy selects several areas for comparison--the capitals, the legions, the fixers, the outsiders, and the borders--mines his ancient and modern popular cultural referents, and then offers the cookie-cutter results. That Murphy is witty, writes well, is well versed in irony, and understands the excesses of American popular culture still does not mean that his conclusions are not mostly as superficial as they are predictable: "Rome displayed the attribute of any great capital with more hubris than humility: the overweening self-regard, the presumption that it knew better than others, the surprising ignorance about foreign cultures, the languid arrogance, the competitive displays of wealth ..."

In truth, Rome knew far more about foreign nations than any one of them did about Rome. There was simply nothing comparable in Numidia, Parthia, or Germany to the anthropology evident in Caesar's Gallic War, Sallust's Jugurtha, Pliny's Natural History, or the Germania and Agricola of Tacitus, which all reveal Rome's near-obsession with the political and natural history of its neighbors.

When we get to the American side of that equation we unfortunately reach the same reductionism: "Dick Cheney's travel requirements became public in 2006, revealing that when he entered a new hotel room he wanted all the television sets already turned on and tuned in to the ideologically congenial Fox News." But that tidbit about the cause and effect between insular news and blinkered politics has about as much relevance to the notion of America as Rome as the fact that media spinners like Chris Matthews, Bill Moyers, George Stephanopoulos, and Tim Russert all came to their glamorous media craft from prior partisan-political careers.

Murphy's military comparison should be more fertile, since--like Rome--we have an army that is relatively small, professional, and voluntary. Yet here too we get the same simplification--e.g., the observation that such nicknames of Roman legions as "Thunderbolt" (Legion XII Fulminata) conjure up our own "Iron Horse" (the 4th armored division), or the profound statement that "yesterday's Conan the barbarian is Conan the contractor."

About this last, it should be observed that all large militaries contract out services. The Ottoman fleet was run by renegade Italian admirals. The British 19th-century military ruled the world with a tiny force supplemented by indigenous hires. The French Foreign Legion is not much French. In fact, purely mass-conscription civic militaries--whether the Roman army that beat Hannibal or ours that defeated Hitler and Tojo--are rare in civilized history. More important, the current education level of the U.S. military now exceeds that of the general population. Its private contractors are subject to a level of official and media scrutiny unknown in Roman courts. The Pentagon operates under oversight unimaginable among Roman proconsuls.

For the similarities to Roman "fixers" we get most prominently Jack Abramoff and "the Republican contribution hierarchy"--again with not enough recognition that there is a tradition of criminal prosecution of such malefactors in the U.S. (of a kind unknown in Rome). Nor does Murphy stress enough that the contemporary problem of influence peddling inside the Beltway is bipartisan in nature--as we saw with the serial renting of the Lincoln Bedroom during the 1990s, the Department of Commerce-sponsored overseas junkets, or the pardoning of shady high rollers by the Clinton administration.

Oddly, in a far more introspective conclusion, Murphy settles down somewhat, and offers some thoughtful reasons we need not become an imperial Rome. Here, sounding more like a reverential Livy than a Petronius or Juvenal, he is absolutely right that the amazing American trait of self-reflection and criticism can correct the current malfeasance at home and lapses abroad in a way the imperial bureaucracy of Rome in its last centuries could not--if we remember how and why Americans are not, and should not be, Romans.

Mr. Hanson is a military historian and a senior fellow at the Hoover Institution at Stanford University. His website is victorhanson.com.