I just read the article in today's New York Times Magazine about the Dutch-Somali ex-Muslim member of the Dutch Parliament, Ayaan Hirsi Ali, and found it very disturbing for what it says about the relationship between liberalism and extremism. The author of the article, Christopher Caldwell, argues that it was Dutch liberalism that permitted the growth of an alienated Muslim immigrant population in the Netherlands that now includes many people who have embraced the ideology of Al Qaeda and militant Islamism.

Until recently, the Netherlands adhered to a national policy cumbersomely known as ''integration with maintenance of one's own identity.'' It arose partly out of unspoken guilt over the country's failure to save many Jews under German occupation during World War II and partly out of a modish multiculturalism. But letting ethnic communities go their own way also had a long history in the Netherlands. The ''Pacification'' of 1917 formalized a system in which different groups - Catholics, Protestants, secular citizens and others - lived in separate institutional universes, or ''pillars.'' A Catholic would typically attend a Catholic school, read a Catholic newspaper, join a Catholic trade union and social club and vote for a Catholic political party.

The system withered in the 1960's, but many Dutch clung to the hope that its virtues could be revived for an age of immigration. In the early 1990's, Frits Bolkestein, then the leader of the country's pro-free-market party, the VVD, warned in articles and speeches that they could not. He argued that certain identities, unlike the old Catholic and Protestant ones, would, if maintained, undermine the individual rights that are at the heart of the Dutch constitution. He cited the practice of bigamy, for instance. Where clashes occurred, Bolkestein insisted, Dutch norms must prevail. For this observation, he was condemned as a rightist and a racist. Today, most Dutch accept the validity of Bolkestein's critique, even if they can't agree on what to do about it.

Hirsi Ali says that it is not just militant Islam that is the problem - it is much of traditional Islam as well. She began to speak up after the terrorist attacks of September 11, 2001: " She took the floor at a conference in an Amsterdam political club to say that what Islam needed was not understanding from others but its own Voltaire. The national daily Trouw had her write an op-ed on the matter. Asked her opinion of Pim Fortuyn's characterization of Islam as a 'backward religion,' Hirsi Ali replied that by certain measures, including the treatment of women, Fortuyn's statement was not an opinion but a fact."

Eventually, she and Theo van Gogh, an outrageous Dutch filmmaker, made a movie called "Submission" - "It presented four fictional episodes. All involved violence against women and the Koranic verses that had been, or could be, used to justify it. These verses were written on the skin of the actresses' seminaked bodies." Van Gogh was murdered by an Islamist terrorist, and "Hirsi Ali says she felt guilt over van Gogh's death - guilt that van Gogh's mother publicly insisted was misplaced -- but she continues to reject any suggestion that the film they made was sensationalist, or gratuitous in its use of see-through clothing. 'Maybe Americans think, "This is a naked body,''' she says. 'But this body is why half the nation in Saudi Arabia is not allowed to drive.'''

The predicament of individual Muslim women has become a public concern in the Netherlands. In February, the daily Volkskrant ran an expose of widespread bigamy among Dutch Moroccans. Muslim views on virginity have led to other clashes. There are clinics that specialize in the surgical repair of broken hymens, a practice that was often covered by national insurance until the ministry of health blocked it last May. Genital mutilation, of the sort practiced on Hirsi Ali and 98 percent of girls in Somalia, has been illegal in Holland since 1993 but still occurs.

Hirsi Ali says of herself, "I confront the European elite's self-image as tolerant,'' she says, ''while under their noses women are living like slaves.''

Hirsi Ali raises the question of whether a liberal society that values multiculturalism must accept all possible values in order to be tolerant. Are there certain liberal principles, such as the belief in the equality of human beings, or the emphasis on individual rights, that must override tolerance for the principles of other cultures? In the U.S., this has certainly been true. For example, Utah was only able to become a state when it outlawed polygamy, which had previously been permitted by the dominant Mormon church. If people come to the U.S. from countries where polygamous marriages are permitted, they can't continue to engage in polygamy here. The Supreme Court has generally upheld the ability to hold different religious beliefs, but frowned on accepting different religious practices that collided with the dominant Protestant model of what religion is - for example, not upholding the rights of Native Americans to eat peyote as part of a religious ritual. [My former colleague, Eric Mazur of Bucknell University, is the person who taught me this approach to religious freedom in the United States - see his recent book, Religion on Trial: How Supreme Court Trends Threaten Freedom of Conscience in America.]