Nathan Gardels is the editor of NPQ.

I understand why Bernard-Henri Levy wrote this book. For journalists and writers who go out to engage the world in good faith, the slitting of Daniel Pearl's throat in the same merciless manner as slaughtering a lamb at the end of Ramadan felt more brutal -- because it was more direct and personal and thus more imaginable -- than the horrific crime of flying planes into buildings and killing thousands. This recoiling emotion hits the reader within the first graphic pages of Who Killed Daniel Pearl? But Levy's existential repugnance points from the outset to something more: This decapitation of an open mind in a dark, windowless room on the grimy outskirts of Karachi is emblematic of the confrontation between liberal civilization and violent obscurantism that now engulfs us. It is the compelling tale of our time.

As Levy unravels in his investigation, and as United States intelligence now confirms, Pearl's killers were part of the same shadowy web of fanatic jihadists that carried out the World Trade Center attacks. There are recent reports that while Omar Sheikh, who has been convicted and jailed for the crime, was the front man for the kidnapping, Khaled Sheikh Mohammed, the operations chief of Al-Qaeda, has confessed in American custody that he personally drew the knife across the journalist's neck.

More worrisome for the future, as Levy sketches out, this web encompasses not only key members of the Pakistani secret services, the ISI, but claims the allegiance of some of that country's top nuclear scientists who proudly take credit for creating "the Islamic bomb." Rightly, Levy's book concludes with this inescapable question: If the Islamic bomb fell into the same hands that slashed Pearl's head from his body, is there any doubt it would be used?

Like most commentators, Levy hastens to add that he doesn't accept Samuel Huntington's thesis of a clash of civilizations between Islam and the West, but sees instead a conflict between "Muslim moderates" or "gentle Islam" and "radical Islamists." Yet in setting up the protagonists of his journalistic novel as Daniel Pearl and Omar Sheikh he is, in effect, positing an echo of Huntington's thesis that, indeed, this is a clash of civilizational outlooks, ways of life and historical experience.

Levy hints at, rather than recounts, the significance of Daniel Pearl's upbringing. He was a child of California suburbia with its shopping malls, swimming pools and San Fernando Valley synagogues. Like America as a whole, but more so, California is a geocultural therapy for history's wounded masses. When immigrants get off the boat, they leave their troubles behind. The soil -- ancestral territory and all its baggage -- is taken out of the soul and becomes real estate. The future, not the past, occupies their imagination.

Unwounded in this historical sense, Danny Pearl was secure in his Jewish identity. Unlike his grandparents in Europe, he and his family were first-class citizens with no opportunity denied them and protected by the rule of law. All this made Danny open to the world, not fearful but curious and cosmopolitan.

The British-Pakistani plotter of Pearl's murder, Omar Sheikh, grew up on the edge of London, and like one of Salman Rushdie's divided personalities in Satanic Verses, he was insecure about his identity. His father was a prospering businessman and life was certainly better than it would have been in Pakistan. But as ex-colonial Paks they lived in a second-class statusphere, a latent resentment residing beneath their assimilation.

It surprises Levy -- as it surprised many people when they discovered the Sept. 11 suicide attackers were educated Saudis and Egyptians -- that Omar attended the London School of Economics (LSE). How could someone so enlightened become so cruel and hateful, Levy wonders? The Third-Worldist vogue often found among LSE students notwithstanding, anyone who has traveled in North Africa and studied the Islamist movement would not find this strange.

A look at the science and engineering faculties of all the major schools from Egypt to Tunisia to Morocco make it clear that first-class education conjoined with second-class status in the global scheme of things, or the perception of it, leads in a militant direction.

Though he had no personal experience of it, as Omar grew into adulthood the historical wounds of colonial humiliation lived on and seemed to grow within him into a kind of hatred that lay beneath the veneer of his adoption of all things British. Levy does not make it clear, and perhaps it is unknown to Omar himself, if any particular event caused this shift. As with so many South Asians I know in London, it seems Omar was like one of Isaiah Berlin's "bent twigs" poised to spring back after being stepped upon.

In an earlier era Omar might have become a fervent nationalist like Ho Chi Minh as he labored invisibly at the lowest jobs in Paris, or perhaps a Nazi-inspired Baathist. In spirit, Omar was surely a follower of Franz Fanon who justified violence by the Earth's wretched. But after the failure of post-colonial states and father-like strongmen from that earlier era, the defensive ideology of political Islam arose as the new alternative. That is what attracted Omar. He became one of those combustible Muslim militants who, in the words of V.S. Naipaul, "blamed their misfortune on the success of another civilization."

Feeling more and more contaminated but never fully accepted, it seems Omar began looking for a purity of identity in several Muslim causes, from Bosnia to Afghanistan to Kashmir.

As Paul Berman insightfully notes in his essay, Terror and Liberalism, this yearning for purity is what lay at the root of all fundamentalism -- whether based in race, class or religion. It is the impetus of obscurantism, of the impulse to close off instead of open up, to exclude instead of embrace. In short, it is the opposite of everything liberal civilization stands for.

In this sense, the murder of Danny Pearl was more than the murder of a Jew. It was a striking out at the impure cosmopolitanism of the American-led liberal civilization which shaped him. It is this theme that makes Levy's book important.

In a conversation we had in Paris last January just after he returned from a trip to Pakistan, Levy made the case that "in the recent history of humanity, the hatred of America has been one of the main structural links between the three totalitarianisms -- fascism, communism and Islamism." If one can manage to separate the disastrous policies of the Bush administration from the idea of America, there is much truth in Levy's hypothesis.

Most of the rest of Levy's book reads, often compellingly, like a detective story, unfortunately including too many dead ends and cul-de-sacs in which the thrill of the chase results in the inevitable dissapointment of leads that went nowhere. The chapters trying to unravel the connections and competitions among the bewildering welter of Islamist groups and their members with aliases and different spellings of the same name serve both to put off the reader while at the same time to make his point: The terror network is so opaque and complicated as to be virtually impenetrable.

Finally, Levy makes a convincing case of the links between Islamist terror groups and the Pakistani secret service. "Karachi is the base of Al Qaeda today," he told me when we talked in Paris. "Inside the secret service are those who may not wear the beard of the Islamists, but whose minds are bearded." Authoritative voices concur.

Two days after Sept. 11, 2001, former Pakistani Prime Minister Benazir Bhutto detailed for me the extensive links between the Taliban, Al Qaeda and the Pakistani ISI, or secret service, which she called "a state within a state" that time and again sought to destabilize her government. "Islamabad is the jugular vein of Kabul," she told me at that time, when the Taliban and Osama bin Laden still ruled Afghanistan. If you want to fight terrorism, she said, you have to start in Pakistan.

Bhutto remains convinced, however, that Pakistan's nuclear weapons are still firmly under the control of the military, which, she says, has historically been a disciplined force insulated from the influence of the secret services.

The question for Levy, as for all of us, is what happens if the roiling Pakistani political cauldron comes down -- as a result, for example, of further disaster for the Palestinians or because of the protracted US occupation of Iraq -- on the other side in the clash with liberal civilization? In that not far-fetched circumstance, even Bhutto worries that the army's discipline could break down. "Then," she says, "the security of the weapons of mass destruction would be at risk." Levy's nightmare would be realized.

Levy's ultimate thesis that Daniel Pearl was killed not only because he was a Jew and an American, but following a story that linked Pakistani nuclear scientists to Osama bin Laden and a deal with North Korea, may or may not be true. Truth or not, such informed speculation should be received as a warning. Bernard-Herni Levy deserves credit for declaring loud and clear what is at stake.