Eight years ago this week, Mohamed Atta was in New York City looking for a flight school.

Atta, a zealous anti-Semite from Egypt who believed that Jews were controlling the world from their secret headquarters in New York City, was a new kind of enemy for the United States. He was not a soldier in the army of an enemy nation, but something more like a free agent or entrepreneur of mass murder, who had essentially contracted with al-Qaeda to carry out the most ambitious terrorist attack in history.

As we near seven years into the "war on terror," there are new Mohamed Attas out there. Stopping their attacks is one of this country's essential priorities, but it is not the only one. As we prepare to elect a new president, we have an important opportunity to assess anew what this war means, and how it should be fought.

Al-Qaeda, the author of the 9/11 attacks, is a global network unlike any seen before. Apart from its particular beliefs and goals, it sprang from the rarified atmosphere of the modern world, and long after Osama bin Laden and his gang are a footnote to history, the threat they posed will remain. The terrorists of the 21st century will not necessarily all be Islamist; in fact, beliefs will matter less than methods. It is terrorism itself that poses the threat.

Al-Qaeda has just pointed the way. It has employed the tools of the emerging international market state, air travel, and the ability to transfer money and information worldwide. It has plotted, recruited and instructed martyrs, and advertised its goals and accomplishments via satellite phones, the Internet and international media. In the near future, it and other networks like it will be able to buy terrible weapons off the shelf and seek to detonate them in congested urban centers where they will do the most harm. They are the curse of the modern age, and like the curses of previous eras, they mirror the law-abiding, civil societies they threaten.

This is the threat outlined succinctly in Terror and Consent, Philip Bobbitt's remarkable effort to make sense of our post-9/11 world. Bobbitt - director of the Center for National Security at Columbia University - describes our era as the "market state," as opposed to the nation-states that dominated the 20th century. The nationalist rebel movements of that century sought primarily to supplant government in their own countries and modeled their own hierarchy on the governments they opposed. So today's terrorist networks are international and stateless. They are modeled after the global institutions that define the nascent market state. They seek to undermine the partnerships, security, and rule of law that enable free trade and prosperity, replacing our "state of consent" with a "state of terror."

Better than anyone I have read, Bobbitt has thought through both the nature of the danger and how we should defend ourselves from it. He is no alarmist. Al-Qaeda itself does not pose an immediate threat to our way of life, but the implications of its successes are disturbing. They suggest that our security can no longer be protected by the mighty war machine that defines the United States as the world's superpower. Our military, unmatched in fighting the last great wars, is already an anachronism.

In the years since Atta and his men slammed planes into the World Trade Center and Pentagon, the United States has lashed out violently in a variety of directions, sometimes effectively, often not. President Bush has been decisive and consistent, to a fault, but also incoherent. Congress has become a persistent critic, but has offered little else. We need a strategy that rises above political partisanship and the bromides of a presidential race, one that clearly defines not only what we are fighting against but what we are fighting for.

One first step is to acknowledge the severity of the problem. Terrorism is not simply a law enforcement issue, although combating it may mean blending military and police methods. Terrible weapons once possessed only by powerful states today are becoming available on international black markets. The technology and materials to build them are already for sale, and it is likely that soon the weapons themselves will be. There is not only the terrible loss of life and economic damage to consider - but also the fate of civil liberties and the rule of law after a major attack that kills not just thousands, but tens of thousands. The assumption of war powers by the Bush administration in the years after 9/11 will seem benign by comparison.

What we fight for is the safety of civilians to live normal lives free of chaos and catastrophe, and the preservation of democratic, law-abiding states that respect human rights, what Bobbitt calls "states of consent."

The enemy seeks a "state of fear," and not just in al-Qaeda's ludicrous, cruel and imaginary caliphate. They strive to sow enough fear to topple the normal workings of a free society. We protect ourselves not just by controlling how we respond to acts of terror - as my Atlantic colleague Jim Fallows has suggested - but also by preventing such acts.

Prevention, or what Bobbitt calls "preclusion," means uniting the considerable moral, military and economic clout of the modern market state - that is, global cooperation on an unprecedented scale. Liberals will gladly embrace the importance of such alliances (it is a cornerstone of the campaigns of Barack Obama and Hillary Rodham Clinton) and the need to function within the law, both domestic and (such as it exists) international.

Government also must get better at responding to calamity, both man-made and natural. Part of protecting civilians and preserving free institutions is the ability to recover rapidly from disaster, whether it be Hurricane Katrina or a dirty bomb in Chicago. The growing concentration of population around urban centers, and quite possibly the effects of global warming, make more likely catastrophic events that undermine the rule of law. Civil defense has been a poor stepchild in the world of national security; in the 21st century it has become an urgent priority. When the United States has deployed its military power to assist those stricken by disaster around the world, it has done a great service to the cause of freedom.

But responding to such threats will also mean adapting American law to deal with a changing world. Civil defense in this country should become a military mission, which means breaking down some of the antiquated barriers that prevent an aggressive, rapid federal response.

Preventing damaging attacks also means enacting laws that enable sophisticated, time-sensitive intelligence-gathering, such as data-mining and global electronic eavesdropping. It also means wading into the morally uncertain terrain of interrogation: How to acknowledge the necessity of gathering intelligence, while avoiding the scandalous, stupid and self-defeating excesses at Abu Ghraib and Bagram?

Those who say, "Protect civil liberties at all costs" should soberly assess the consequences to their own cause of failing to preempt significant attacks. If the consequences of failure are the loss of all civil liberties, then sensible adaptation would seem part of the genius of democracy. In football it is called "bend but don't break."

This presidential election provides us with a new opportunity to focus our national effort effectively, to make it clear to the world that we stand for the rule of law, government by consent, and the protection of human rights, and aim to defend ourselves from those who would deny them. The law should protect us from the excesses of government, but first and foremost it ought to protect us from foreign enemies.

As Bobbitt writes, "For all the good work they do, the chief protector of American constitutional rights is not the Lawyers Committee for Civil Rights or the American Civil Liberties Union or even the Supreme Court; it is the 101st Airborne Division."

The Bush administration's contempt for the strict rule of law and disdain for international consent have all but discredited the notion of self-defense against this modern threat. It failed to realize that legitimacy and legality are not always constraints on power, but powerful tools against those who would impose their will with terror. A new president and administration have an opportunity to enunciate a strategic doctrine that clearly puts America on the side of protecting civilians, preserving the rule of law, the principle of consent, and defending the pursuit of life, liberty, and happiness.

Mark Bowden is a former staff writer at The Inquirer and is now national correspondent for the Atlantic Monthly. Contact him at mbowden@phillynews.com.