[Mr. Laqueur, a historian, is the author, inter alia, of "A History of Terrorism" (Transaction, 2001).]

It is not “the West against the rest.” All throughout human history, civilizations have coexisted and competed, and there is no good reason to assume that this will change in the foreseeable future. True, there is still considerable resistance to accepting such obvious facts as, for instance, the shrinking importance of Europe—demographically, economically, politically—even though the rise and decline of civilizations is a phenomenon as old as the hills. The position of America in the world without a strong Europe will certainly be weakened.

But looking ahead, the present threat is not really a “clash of civilizations,” but fanaticism and aggression, which are of particular importance in an age of weapons of mass destruction. There is no need to spell out where fanaticism is most rampant and dangerous at the present time. But it is less clear how durable fanaticism is, how long its intensity will last.

History seems to show that it is largely (albeit not entirely) a generational phenomenon. It seldom lasts longer than two or three generations, if that. How little time passed from the desert austerity of early Islam to the luxury of the Abbasid court in Baghdad! The impetus which led to the the Crusades petered out in several decades. More recently, in the age of secular religions such as Communism, fanaticism (even enthusiasm) evaporated even more quickly. The pulse of history is quickening in our time, everywhere on the globe.

All of which leads to the question: what undermines and weakens fanaticism, aggression and expansion—and what follows it? (In some respects this resembles the debate prompted by Leon Festinger a few decades ago: what follows if and when prophecy fails?) The importance of economic factors in this context has been exaggerated (with certain exceptions); the impact of culture (in the widest sense) has been underrated.

It is a phenomenon that can perhaps best be observed among the Muslim communities in Europe. On one hand, there has been palpable radicalization with the emergence of a new underclass, the failure in the educational process, the sense of discrimination, the search for identity and pride. There seems to have been the emergence of what was called in nineteenth-century France les classes dangereuses. But even in these social strata, it is becoming more difficult to keep the fold in line. As a leading Berlin imam put it, the road to the (fundamentalist) mosque is long, the temptations are many and “we are likely to lose about half of the young on the way.” It is a process which virtually all religions have experienced, and Islam seems to be no exception. The importance of the street gang (as yet insufficiently studied) could be as great as that of religion or ideology.

There is the contempt for Western decadence as expressed for instance in the growth of pornography denounced by Muslim preachers. Pornography has a very long history. It is a term often used loosely and arbitrarily; views and attitudes have radically changed in time and not only in Western culture. Kleist’s Marquise of ‘O, a novella published two hundred years ago, was dismissed as pornography at the time. Today it is deemed a jewel of world literature and no one would consider it particularly erotic. For centuries, there has been an erotic strain in Islamic literature, and greater experts than I have written about it. Salafis now regard it as pornography, which is haram because it is fahsha (obscenity, abomination, fornication) as stated in the Quran.

But the preachers seem not to have been too successful. The list of the countries with the most frequent surfers on the Internet looking for “sex” is headed by Pakistan, followed by India, Egypt, Turkey, Algeria, Morocco, Indonesia and even Iran. As Oscar Wilde sagely noted, he could resist anything but temptation—or as the New Testament puts it, the spirit is willing but the flesh is weak.

In brief, there is a tremendous difference between the holy writs and their exegesis and the reality in matters sexual. And this is true for many aspects of modern mass culture. After the Iron Curtain had come down and the cold war had ended, some astute Soviet observers noted that the Beatles had played a role in the breakdown of the Soviet empire. I’m in Love and Good Day, Sunshine probably did not play a decisive political role in the fall of the Soviet Union, but they were part of an underground culture which spread and contributed to the gradual subversion of the official secular religion to which everyone paid lip service.

Sexual issues and mass culture have been mentioned as a mere examples; many other factors contribute to the dissolution and breakdown of fanaticism. The point is that the fanatical impulse does not last forever, and it may peter out more quickly than we tend to think today.

But this should not lead to a feeling of great relief—the assumption that the danger has passed and that all we have to do is to sit patiently and wait. It could still be a process of a few generations, and the question arises whether that much time is left to humankind to avert a disaster (or disasters). For the first time in history, small groups of people will have the potential to cause millions of deaths and unimaginable damage; no great armies will be needed for this purpose. It is a race against time.