On that quiet, halcyon September morning of 2001 when first one Boeing 767 heavy with fuel and bound for California, and then another, flew silently into the two towers of the World Trade Center, and within seconds burst into orange balls of flame coming out the other side, something metaphysical in the structure of our world, not just psychological, snapped and came alive.

I do not mean just in the American world, although of course I am thinking especially of that. I mean the Islamic and the Arab world, as well. And Israel's world.

The Greek word for crisis means a decision point, a fork in the road, with enormous consequences riding on the direction taken.

US President George W. Bush very quickly put that point into words: all countries must know that they are either with the terrorists, or with those determined to protect liberty.

Listen up, everybody. Make a choice.

Join the losers. Or the winners.

For Muslims, this means a chance to rescue the high religious purity which many of them find in the Koran from the low, distorting misuse of it for vindictive, hateful purposes. Vicious political cadres with no real interest in religion as religion but only in their own mean gratifications, have by violence and threats hijacked the prayers of a silent majority. For 40 years, they have preached hatred and murder with intensifying ferocity.

Dozens of nations that in 1945 had been overrun by foreign invaders or held in colonial status have by now become independent states, to the applause of a welcoming world. Most did this by winning international respect for their own habits of self-government, the ratification of a decent constitution, and the election of internationally admirable (or at least acceptable) leaders. The emergence of such nations, at least when they were democratic and capitalist, improved the whole world's sense of movement toward peace and prosperity for all.

Won't the Muslim nations now be called onto that path, even by their own long-suffering people?

Preoccupied by the threat to democracy and human rights posed by the Communist powers, the free world paid almost no attention to the lack of democracy, the daily abuse of human rights, and the unnecessary poverty and lack of education in the Muslim world. It is as if during all those years no one paid attention to the suffering of the Muslim multitudes, and the continuing insouciance of their elites.

That is one of the realities that snapped on September 11. Eleven of the hijackers were citizens of Saudi Arabia, and not from among the poorest but from among the educated elite sent abroad for studies. A sudden white glare was cast upon the Arab world, brilliant as the noonday sun. There is no longer any place to hide.

Where terror grows, it must be eradicated.

Where poverty is widespread in the very midst of uncommon wealth, it must be rapidly and steadily diminished by new systems of opportunity and progress. Rights of inquiry, conscience, and personal privacy and initiative and development must be established. The right to worship God as one chooses must be respected, for also in the Koran--so Koranic scholars assure me--the Almighty made humans free, to worship Him in spirit and truth.

At least in the United States, September 11 demanded a new mission for the Arab and the Muslim world. We mean to declare and to work for the same rights for that world as we have declared for ourselves. They are human rights, not American rights. We regret our lack of attention to the sufferings of the Muslim world since World War II.

We have seen in Afghanistan and even in Iran the disgust of many Muslims who had been forced to live under a peculiarly politicized distortion of Islam, and the joy among the Afghans in early 2002 at having their true rights returned in a new democracy.

There are many reasons to believe that, one day soon, the same joy will be visible in the streets of Iraq and, at some time after that, in Iran. The people of these great nations deserve to live in a dignity and liberty they have not tasted for many suffering years. And they will.

But let me return to what snapped in the US on September 11. At least at first, the gradual trend toward multicultural relativism snapped. "Well," people were getting accustomed to saying, "we can't be judgmental. You may look at things one way, but other peoples look at it another way. There's no such thing as good and evil. There's only preferences. Yours, his, everybody's, it's all the same. It all boils down to tolerance." Sorry, as the two towers slid down rapidly from floor to floor entombing hundreds of living human beings in the fire and ash, Americans rediscovered an evil that was not just a preference like any other. This one had to be rejected, stopped, and as far as possible torn out by its roots.

Metaphysically, the category of evil came back into civilized discourse.

Indeed, a deeper point was grasped. Civilization arises from a grasp of the distinction between good and evil. Intellect is capable of recognizing that difference, and of giving arguments to support its judgments on the matter. Reasonable humans may disagree, but as long as they hold to their mutual respect for evidence and argument, they can continue to converse, and to make some progress in doing so. The minute they say, "It's all a matter of preference, and we'll have to settle it by force," civilized argument ends.

Civilized people argue in the light of evidence, with respect for the truth that neither may own but both pledge allegiance to. Civilized people converse. Barbarians club one another.

Another rediscovery is that some things are so evil and so threatening that they must be resisted, even at the cost of one's own life. The terrorism exemplified in September 11 is one of them. Those intent on keeping civilization alive and intact must resist such threats in a fight to the death. And they must prevail. As being must prevail over nothingness. As creation must prevail over destruction.

September 11 brought Americans, at least, back to such basics.

In Europe, by contrast, the horror over what happened may have been the same, but the interpretation was filtered through a different lens.

Europeans enjoy looking down on Americans because we tend to be, they think, fundamentalist and immature. We, for instance, by a large majority believe in God. On September 11 or shortly after, 91 percent of Americans report having prayed for the victims or their families. Some 53 percent report having taken part in a public prayer service in a church, synagogue, or--yes--a mosque during that week. That's more people, a lot more people, than have ever done one thing in America at the same time, even watching the most widely watched television show in our history.

The Europeans seem to pride themselves on being less religious and more cynical than the Americans. The Americans--at the United Nations Human Rights Commission, for example--really do make other peoples feel uncomfortable with the passion that the American people insist that their delegations bring to it. Sorry, but that's the way we are.

Among us, right from 1776, both reason and the Jewish-Christian revelation have been looked upon as parallel arguments on behalf of the centrality of liberty in the metaphysics of the cosmos. According to the Bible, God created the world so that somewhere in it there would be at least one creature, male and female, to whom He could offer His friendship, in such a way that it might be accepted freely, or freely rejected. The God of the Hebrews (and later the Christians) desired the friendship of humans who are not slaves, but free women and free men. This religious argument for universal liberty broke the mold of classical pagan philosophy, which held that most humans are by nature slaves.

Modern philosophers such as Algernon Sidney and John Locke came more easily, then, to fresh ideas about limited government, the protection of rights, and the suitability of human nature to a republican form of government. The US Founders took comfort in the consonance of Scripture and Reason in supporting the cause of liberty. Even Tom Paine, the least orthodox among them, wrote in the Revolution's darkest days that he was "not so much of an infidel" that he believed the Creator would abandon them, just when they had committed themselves to the liberty He taught them.

As Alexis de Tocqueville pointed out in luminous passages in Democracy in America, this confluence of the spirit of liberty and the spirit of religion in the American experiment is of great importance to the human race. It has special relevance following September 11.

There is a tendency in some important quarters of the Islamic world to imagine that reason and "the secular" are opposed to religion. It is true that these may in some cases be opposed. But they need not be. In fact, they most often are not.

Would it not be an absurd world if the Almighty Creator of all things contrived them in such a way that what we learn through the faithful and true use of our reason were flatly contradictory to, and impossibly incompatible with, what we learn through His prophets? That would be bizarre, indeed.

I do not wish to wander here into the many centuries of philosophical and theological debate in all three traditions--Jewish, Christian, and Islamic--about how to relate faith and reason.

Nonetheless, intended or not, the deepest effect of September 11, 2001, was to link together the three great monotheistic religious traditions that arise from the Middle East in an entirely new project. That project is to search out a way toward democratic habits of mutual respect, while using both faith and reason in the service of human liberty.

I have read Natan Sharansky on the universality of democratic longings and capacities. He is right. If we wish peace, we must build democracies, whose sources lie both in reason and in faith.

The US is characteristically slow to become fully aroused and fully engaged. On September 11, that great snapping noise the world heard was Uncle Sam turning his head and fixing his gaze. We do not normally rest until we succeed.

And we in the US see that this current crisis is a particularly deep one, whose roots go all the way down into the metaphysics of liberty, into the way human beings think about liberty, and into the way human beings pray in liberty.

We have some quite worldly business to take care of: to deprive terrorists of arms, training, and breathing space; and probably to help one or two regimes to rearrange themselves into systems that respect the dignity of their citizens, in the hope that others will follow.

But we are also peering pretty steadily into the depths of the spiritual and intellectual problems that confront us. Those, too, need a lot of work. September 11 shook the world to its metaphysical foundations.

The 20th century may have been preoccupied with the political problem of dictatorship vs. democracy, and then the economic problem of socialism vs. capitalism. But the preoccupations of the 21st century are going to have to plunge down to a rather deeper and less familiar level than that: to questions of liberty and dignity, in the light both of reason and revelation.

And not only to such questions as they have so far appeared in one or two traditions only, but in several traditions at once.

Nor will it be possible for atheists to get by either, merely by saying that the only solution is for everybody else to become like them. There is some rethinking to be done in all camps about mutual (if grudging) respect and mutual intellectual interdependence.