You burst into the room. Sitting on a chair, blindfolded, his hands tied behind his back, is your prisoner. The room is dark, except for a lonely naked bulb hanging from the ceiling. He is sweating. He is afraid.

"Tell me where it is!" you scream. "Now!" You know there is little time left. Somewhere in your city, a time bomb is ticking. Whether it spits serin into the air, uranium into the water or atomic fire into the heavens, you do not know.

He does. But he is not talking. Involuntarily, you raise your hand as if to strike. What you are about to do violates the law and your conscience. And yet...

In peacetime, torture ranks next to murder as a primal sin. But during war, the debate begins over whether this evil can ever be justified to combat the seemingly greater evil of the enemy. Harvard law Professor Alan Dershowitz has said torture should be legalized.

In early October, the U.S. Senate voted 90-9 to ban it. Although Secretary of State Condoleezza Rice and President Bush have both recently asserted that "We do not torture," five U.S. Army Rangers were charged in November for punching and kicking detainees in Iraq, secret U.S. prisons have caused anxiety in Europe, and Vice President Dick Cheney has battled to win the CIA an exemption from the torture ban. As late as December, the U.S. House of Representatives stood poised to defeat the White House.

Few of us will ever be asked to torture. But, indirectly, all of us have to make a choice: to support, as citizens, those politicians who back torture, or those who seek its prohibition.

The decision of an individual to support, or reject, torture seems at first to be a purely moral question. But what would be the long-term consequences to society if we were to make this radical break with the past?

One cannot do experiments with societies, or predict the future, but, it turns out, one can attempt to address this issue using the cold, hard tools of mathematics and logic. This story begins in 1963.

The United States and the Soviet Union are on the perpetual brink of war, balanced like two sides of an equation. On the American side are "game theorists" like Thomas Schelling, recently awarded the Nobel Prize for his work on the strategy of conflict. On the Soviet side, there is the solitary mathematical psychologist Vladimir Lefebvre.

Just as mathematics could be used to describe logical reasoning, Lefebvre saw that mathematics could be used to describe ethical reasoning. If something was good -- for example, "church," "democracy," "prosperity," "kindness" -- it had value "1."

If something was evil -- "earthquake," "famine," "military defeat," "murder" -- it had value "0." But rarely were ethical situations so simple. For instance, "killing" is bad (0) but protecting one's country is good (1) -- so is war 1 or 0?

Lefebvre saw that, at the crudest level, there were essentially two types of ethical systems. Those that held that employing evil means to attain just ends was good, and those that saw that employing evil means to attain good ends was wrong.

There were also, crudely put, two types of relations between individuals: those entailing compromise (or cooperation) and those entailing confrontation.

Of course, evil people rarely see themselves as evil. So Lefebvre had to incorporate in his model of human nature the capacity of human beings to judge -- correctly or incorrectly -- the goodness or evil of their own acts, and to reflect upon their own judgments, and others'. "Reflexive Theory" was born.

It quickly became a paradigm within the Soviet defense establishment, with the publication of books such as "Mathematics and Armed Conflict." Nothing like it was known in the West.

With very simple assumptions -- for instance, that an individual who correctly sees his actions to be good when they are good, and evil if they are evil, is more highly regarded by society than an individual who incorrectly sees himself -- Lefebvre showed that in a society that accepted the compromise of good with evil, individuals would more often seek the path of confrontation with each other.

Lefebvre's insights were called upon by the State Department during negotiations with Mikhail Gorbachev in Reykjavik, Iceland. (And perhaps Lefebvre's model could be re-enlisted to help U.S. officials understand and negotiate with Arab and Muslim heads of state, who must also negotiate with their people.)

In support of Lefebvre's revolutionary new theory, a survey of Soviet émigrés and Americans was conducted in the 1970s. They were asked questions like, "Should a doctor conceal from a patient that he has cancer in order to diminish his suffering?" Overwhelmingly, the Americans would say no, and overwhelmingly, the Soviets yes. The Soviets accepted the compromise of good with evil; the Americans rejected it.

What does this mean? If Americans begin to accept the use of torture, American society might turn into a society of individuals in conflict.

Not uniformly, thanks to something called free will, but generally, with harmful consequences for society: Imagine two roads, with a stream of cars moving along each one. Each driver wants to reach his destination as quickly as possible; on occasion, drivers will impede each other.

On the first road, drivers rise in their own, and in other drivers', estimation if they yield. Drivers on the second road lose face when they yield. It is clear that traffic will move faster on the first road than on the second.

It can be argued that repressive states like Saudi Arabia, which bred most of the Sept. 11 hijackers, are on the second road. If the United States moved to accept torture, it could veer toward the second road, too -- the road of the Soviet Union.

And we know where that road ends. The Soviet Union no longer exists.

Despite its attempt to soften criticism of the war, there is no evidence the Bush administration is capable of self-correction.

That came home to me the other day while listening to a senior administration official deliver an off-the-record tour d'horizon of American foreign policy. He is among the best minds in this administration, counted among the ranks of the realists, rather than the neoconservatives.

The United States stands alone as the most powerful nation in the world, the official began. In no previous moment of human history has a single state enjoyed such a dominant position.

When it comes to managing its relations with other would-be powers -- Europe, China, Japan and India -- the United States has done "extraordinarily well,'' he said.

The tensions generated by the war in Iraq have eased, the senior foreign policy official confidently asserted. The Europeans are content to gaze intently inward, he observed, while America strides the globe.

Japan is embracing the United States in a very close relationship that shows no sign of unraveling. Meanwhile the Bush administration has forged a growing partnership with India.

When it comes to China, the administration has chosen the path of accommodation and integration rather than containment of the rising power. He expressed confidence that American power and the prospect of democracy in China will secure the peace.

The only remaining challenge for the United States is to combat the threat of a radical Islamist movement that seeks to acquire weapons of mass destruction. For that, there is the promotion of democracy and American values around the world. After all, the official said with not even a nod to humility, "the U.S. is the most successful country that has ever existed.''

A year or two ago, the American people embraced this vision of a confident colossus, a Gulliver among the Lilliputians. That was before they watched the giant tied down in its attempt to export those American values by force of arms in Iraq.

The arrogance of this administration would be barely tolerable if it were not paired with a stunning incompetence, on display from Kabul to Katrina. That deadly combination has weakened American strength in the world. It has emboldened far more serious challengers in Iran and North Korea, who see the United States as too bogged down in Iraq to credibly threaten them with the use of force.

The war rated barely a mention in the sweeping view offered by the senior administration official, except indirectly. He offered a realist defense of the administration's democracy crusade.

World War II was fought with democratic goals, the official pointed out. And the Cold War -- the model for the current struggle against Islamic extremism -- was not just about balancing the power of the Soviet Union. The wars in Korea and Vietnam were really about determining which system those countries chose, he argued.

Those are curious examples to cite as a defense of the decision to go to war in Iraq. The United States shored up authoritarian regimes in Korea and Vietnam to counter the communist threat. Vietnam was a strategic mistake that took decades to overcome. And democracy came to Korea more than 35 years later, after a long period of economic development.

President Bush cited the democratic transformation of Korea -- along with Taiwan and Japan -- in a recent speech during his trip to Asia. But these are examples of the "conventional story in which you become rich and then you become democrats,'' as the senior official put it so well.

The administration proposes however to skip this long, but necessary, path to democratic capitalism when it comes to the Middle East. The policies of security and stability have failed there and a quicker route to democratic change is called for. But there is no historical evidence to suggest that this is any more than another manifestation of a blind belief in American power.

Democratic values have always been essential to American foreign policy. In practice, however, American administrations have often made painful choices between stability and the promotion of democracy. We saw that too often during the Cold War -- in Budapest in 1956, Prague in 1968 or Tibet in 1959.

The administration might do well to recall the words of candidate Bush, uttered Oct. 11, 2000.

"It really depends on how our nation conducts itself in foreign policy. If we're an arrogant nation they'll resent us,'' Bush said. "But if we are a humble nation, they'll respect us.''

In the old popular song about the rout by Americans at New Orleans during the War of 1812, the British "ran so fast the hounds couldn't catch 'em." Even allowing for patriotic hyperbole, it can hardly be argued that the British extricated themselves with a great deal of dignity, particularly given that another battle in the same war inspired the American national anthem.

The impact of that defeat on the British national psyche is now obscure, but nearly two centuries later, as the Americans and their British allies seek to extricate themselves from Iraq, the story of how a superpower looks for a dignified way out of a messy and often unpopular foreign conflict has become a historical genre of sorts. As the pressure to leave Iraq increases, that genre is receiving new and urgent attention.

And in the shadow of the bleak and often horrific news emerging from Iraq nearly every day, historians and political experts are finding at least a wan hope in those imperfect historical analogies. Even in the absence of a sudden and dramatic shift on the battlefield toward a definitive victory, there may still be a slight opening, as narrow as the eye of a needle, for the United States to slip through and leave Iraq in the near future in a way that will not be remembered as a national embarrassment.

Most of the recent parallels do not seem to offer much encouragement for a confounded superpower that wants to save face as it cuts its losses and returns home. Among them are the wrenching French pullout from Algeria, the ill-fated French and American adventures in Vietnam, the Soviet humiliation in Afghanistan and the disastrous American interventions in Beirut and Somalia.

Still, there are a few stories of inconclusive wars that left the United States in a more dignified position, including the continuing American presence in South Korea and the NATO peacekeeping mission in Bosnia. But even those stand in stark contrast to the happier legacy of total victory during World War II.

The highly qualified optimism of these experts about what may still happen in Iraq - let's call it something just this side of hopelessness - has been born of many factors, including greatly reduced expectations of what might constitute not-defeat there. The United States already appears willing to settle - as if it were in a relationship that had gone sour but cannot quite be resolved by a walk out the door, punctuated with a satisfying slam.

Alongside the dampening of hopes, there has also been a fair amount of historical revisionism regarding the darker tales of conflicts past: a considered sense that if the superpowers had made different decisions, things could have turned out more palatably, and that they still might in Iraq.

Maybe not surprisingly, Vietnam is the focus of some of the most interesting revisionism, including some of it immediately relevant to Iraq, where the intensive effort to train Iraqi security forces to defend their own country closely mirrors the "Vietnamization" program in South Vietnam. If Congress had not voted to kill the financing for South Vietnam and its armed forces in 1975, argues Melvin R. Laird in a heavily read article in the current issue of Foreign Affairs, Saigon might never have fallen.

"Congress snatched defeat from the jaws of victory by cutting off funding for our ally in 1975," wrote Mr. Laird, who was President Nixon's defense secretary from 1969 to 1973, when the United States pulled its hundreds of thousands of troops out of Vietnam.

In an interview, Mr. Laird conceded that the American departure from Vietnam was not a pretty sight. "Hell, the pictures of them getting in those helicopters were not good pictures," he said, referring to the chaotic evacuation of the American embassy two years after Vietnamization was complete, and a year after Nixon resigned. But on the basis of his what-if about Vietnam, Mr. Laird does not believe that all is lost in Iraq.

"There is a dignified way out, and I think that's the Iraqization of the forces over there," Mr. Laird said, "and I think we're on the right track on that."

Many analysts have disputed the core of that contention, saying that large swaths of the Iraqi security forces are so inept they may never be capable of defending their country against the insurgents without the American military backing them up. But Mr. Laird is not alone in his revisionist take and its potential application to Iraq.

William Stueck, a history professor at the University of Georgia who has written several books on Korea, calls himself a liberal but says he buys Mr. Laird's basic analysis of what went wrong with Vietnamization.

Korea reveals how easy it is to dismiss the effectiveness of local security forces prematurely, Mr. Stueck said. In 1951, Gen. Matthew Ridgeway felt deep frustration when Chinese offensives broke through parts of the line defended by poorly led South Korean troops.

But by the summer of 1952, with intensive training, the South Koreans were fighting more effectively, Mr. Stueck said. "Now, they needed backup" by Americans, he said. By 1972, he said, South Korean troops were responsible for 70 percent of the front line.

Of course, there are enormous differences between Iraq and Korea. Korean society was not riven by troublesome factions, as Iraq's is, and the United States was defending an existing government rather than trying to create one from scratch.

Another intriguing if imperfect lesson can be found in Algeria, said Matthew Connelly, a Columbia University historian. There, by March 1962, the French had pulled out after 130 years of occupation.

That long colonial occupation, and the million European settlers who lived there before the bloody exodus, are major differences with Iraq, Mr. Connelly noted. But there were also striking parallels: the insurgency, which styled its cause as an international jihad, broke down in civil war once the French pulled out; the French, for their part, said theirs was a fight to protect Western civilization against radical Islam.

Like President Bush in Iraq, President Charles de Gaulle probably thought he could settle Algeria in his favor by military means, Dr. Connelly said. In the short run, that turned out to be a grave miscalculation, as the occupation crumbled under the insurgency's viciousness.

Over the long run, though, history treated de Gaulle kindly for reversing course and agreeing to withdraw, Mr. Connelly said. "De Gaulle loses the war but he wins in the realm of history: he gave Algeria its independence," he said. "How you frame defeat, that can sometimes give you a victory."

The Americans in Beirut and the Soviets in Afghanistan are seen, even in the long view, as cases of superpowers paying the price of blundering into a political and social morass they did not understand.

For the Soviets, that mistake was compounded when America outfitted Afghan rebels with Stinger missiles capable of taking down helicopters, nullifying a key Soviet military superiority. "I don't think they had a fig leaf of any kind," said Henry Rowen, a fellow at the Institute for International Studies at Stanford who was assistant secretary of defense for international security affairs from 1989 to 1991. "They just left."

In Beirut, the Americans entered to protect what they considered a legitimate Christian-led government and ended up, much as in Iraq, in the middle of a multipronged civil conflict. In October 1983, a suicide attack killed 241 American servicemen at a Marines barracks, and four months after that, with Muslim militias advancing, President Ronald Reagan ordered the remaining marines withdrawn to ships off the coast, simply saying their mission had changed. The episode has been cited by Vice President Dick Cheney as an example of a withdrawal that encouraged Arab militants to think the United States is weak.

Today, even as expectations for Iraq keep slipping, some measure of victory can still be declared even in a less-than-perfect outcome, said Richard Betts, director of the Saltzman Institute of War and Peace Studies at Columbia. For example, he said, an Iraqi government that is authoritarian but not totalitarian might have to do.

The key point, he said, is that under those circumstances, the outcome "doesn't look like a disaster even if it doesn't look good."