Many people have said that the obliteration of the World Trade Center marks a turning point -- a day after which the world will never be the same. But in the comments of political and military leaders during the hours when the rubble was still smoking, there was little sign of anything but the same kind of reflexive response to horrific acts that we've seen since the beginning of history. There was the same impulse to seek vengeance, to "hunt down" the perpetrators and "smoke them out of their holes" -- never mind what that effort might cost to those bewildered farmers and herders among whom the perpetrators may now be hiding. Didn’t we learn something about this problem in Vietnam?

As I begin to write this, it is just 24 hours since the World Trade Center and Pentagon were so amazingly and audaciously struck. But already I see signs that we are about to embark on some very dangerous responses:

1. Focusing on revenge. I see a critical difference between delivering justice and wreaking vengeance. In the aftermath of the attack, that distinction seemed to be swept away.

The first public reaction of Mr. Bush, to "hunt down and punish," put out the message that the US will not be bullied. But that’s not likely to have any deterrent effect on committed terrorists, any more than capital punishment has a deterrent effect on ordinary murderers ( numerous studies confirm that it doesn’t). And if the desire for retribution results in US attacks that kill civilians whose deaths can be officially dismissed as "collateral damage," it will more likely enflame terrorist passions – and gain them new sympathizers – than subdue them. It will leave more people around the world believing (as the terrorists may well intend) that it’s the United States that’s the bully.

2. Impulsively pouring more resources into the military. One of the key lessons here is that threats to human security, even if we’re speaking only of the kinds of threats posed by human aggression, now include forces for which military defenses were never designed. Money poured into military defense may be wasted, if ingenious and determined adversaries can find ways to attack without military weapons – relying, rather, on unexpected uses of the routine products of civilian life. The nation that wields the world’s most advanced super-weapons was brought to grief by a few men armed with knives. The Oklahoma bomber, Timothy McVeigh, used farm chemicals and a rental truck. The longer we remain fixated on the outmoded idea that physical security is assured mainly by high-tech military might, the more vulnerable we will be.

3. Forgetting that the worst threats from humans may not be from aggression at all, but from ignorance and miscalculation. Lives are lost regularly, and in dismaying numbers, under circumstance stemming not from evil intent, but from unwitting – sometimes even well-meaning – human disruptions of natural balances. Think of the hillside clearcutting that made way for the catastrophic mudslides that buried whole villages alive during Hurricane Mitch in 1998. Or the over-feeding of antibiotics to farm animals, which helps to breed antibiotic-resistant pathogens and makes us increasingly vulnerable to epidemics in the near future. A life lost as a result of such mistakes is just as much of a loss as that of a life taken by terrorist acts. As human-caused biodiversity loss and climate disruption gain ground, we need to keep our sights clear and understand that the measure of a threat is not a matter of whether it is made on purpose, but of how much loss it may cause. It’s an ancient habit to go after those we perceive to be evil because they intended to do harm. It’s harder, but more effective, to "go after" ( to more effectively educate and socialize) those vastly larger numbers of our fellow humans who are not evil, but whose behavior may in fact be far more destructive in the long run.

4. Assuming that greater security means stronger walls, tighter borders, and isolation of assets. From now on, if the events of September 11 really do prove to be a turning point, human security will not be about technology, but about relationships. It will be about having greater trust in cooperation and community, rather than accepting greater restrictions of liberty and privacy. If the objective is to lower the threat of future terrorist acts, the response should be one that focuses on strengthening relationships with other nations and cultures, not on demonizing them or haplessly trying to keep them out. If US authorities can’t keep thousands of Mexican laborers (who have no particular training in evasion) from walking across the U.S.-Mexican border each year, what makes those authorities think they can keep out small groups of highly trained and clandestine attackers?

5. Opting to decentralize activities like those of the New York financial district -- to move out of city centers and disperse. If lower Manhattan were to cease to be a thriving urban center, the loss – to the city and to the world – would be even greater than the loss of the World Trade Center itself. American cities have been wounded enough, both socially and environmentally, by the flight of residents and businesses from their cores. Lower Manhattan, in contrast, is a vital hub of human commerce and life. If the companies or individuals who make it their home should get scared and decide to leave, the terrorists win. Maybe it’s not important to rebuild a pair of 110-story towers, whose dominance of the skyline may have been too provocatively blatant a symbol of the "masters of the universe" role that makes America so resented in some parts of the world. But when the rubble is cleared, something should be built that says this is a place for people to work together, not to disperse into medieval – or even suburban – isolation.

All of these quick responses result from focusing on proximate threats rather than on systemic explanations. The natural tendency now will be to concentrate on the kinds of spots where we just got hit – on prominent buildings, airport gates, airplane cockpits, etc. Yet, that could simply drive the aggressors to shift to something else. It reminds me of a comment I heard just a few weeks before the September 11 events. I was part of a small group asked to come to U.S. National Guard headquarters to do an assessment of future threats that the military may not be prepared for. Another member of the group suggested that the recent debate about whether Bush’s proposed missile defense system would work may be the wrong debate.

"Suppose it's very effective," he said. "And suppose you're a group determined to attack. What do you do? If you know the missile defense is effective, you eliminate the missile as an option, and do something easier. A jar of smallpox, or a poisoned water supply, or a suitcase nuke."

A suitcase nuke? Now, in the wake of those endless TV reruns of the twin towers collapsing, the very phrase makes me shiver. In the 1970s, I worked as an editor for Theodore B. Taylor, a nuclear physicist who as a young man had designed atomic bombs for the US government, but who had later experienced a profound change of heart.

Taylor had personally designed the largest-yield atomic bomb ever exploded by any government, and he had also designed the smallest one – a suitcase-sized device that doubtless contributed to his subsequent thinking about how wrong that whole super-arms race had been.

By the 1970s, Taylor was spending full time analyzing how terrorist groups or individuals could acquire nuclear materials and expertise, and urgently trying to warn the world of their threat. This was long before we’d heard of Saddam Hussein or Osama bin Laden, but he clearly saw their kind coming. He developed scenarios of nuclear extortion, blackmail, and terrorist attack – just how they could happen – and one of my jobs was to edit the scenarios. For years afterward, I marveled at how lucky we were to be making our way through the 20th century without a major attack by assailants who could not be found, and against whom we had no effective defense.

Even so, what is most vivid in my memory of those scenarios is not the details, but the passionate and unflagging belief of Ted Taylor that the building of such weapons had been a terrible mistake. Maybe the keeping of them is, too. In any case, we have now reached a point where our real hope – perhaps our best hope – is to study far more seriously why destructive people behave as they do. What drives a young Muslim to sign up for bin Laden’s holy war? What leads the advocates of jihad, like those of the crusades a thousand years ago, to think that their God will reward them for annihilating those who do not share their faith?

Until we have answers to such questions, we have little chance of stopping the disruptions that have now begun. We need to begin making major financial investments, not just in improving the technology of security, but in understanding the psychology and sociology of security. What is it, in a child's upbringing, that lets him grow up emotionally secure, life-loving, and looking forward to the future? And what, in another child's experience, makes him reach his early 20s filled with fury and hate -- more than willing to kill himself and others in the pursuit of a mission we can barely comprehend? In studying this question, of course, we may stumble upon new knowledge that tells us more than we expected to find – not just about the motivation of young fanatics with knives, but about ourselves.