BERLIN — In Europe's cafes, the newspapers are as wrinkled as always, the conversations still veer toward the abstract, but tempers these days are riled.
Artists and influential leftists are warning that the rise of radical Islam is threatening the tradition of European liberalism. Theater directors, cartoonists and writers say the continent is betraying its identity by practicing self-censorship aimed at appeasing a fundamentalist Islam they believe is determined to impose its will on free speech and creativity.
The German Opera in Berlin recently canceled its revival of a production of Mozart's "Idomeneo," fearing that a scene showing the severed head of the prophet Muhammad -- as well as those of Jesus, Buddha and Poseidon -- would anger Islamists.
In 2005, the Tate Gallery in London withdrew a glass sculpture titled "God Is Great" because officials did not want to offend Muslims with images of the Bible, Talmud and Koran.
The decisions are part of what liberals regard as a timidity that emerged after the Sept. 11, 2001, attacks in the U.S. and intensified during this year's Muslim protests against a Danish newspaper's cartoon caricatures of Muhammad.
"It's a fear of brutality, and you submit to that brutality," said Henryk M. Broder, whose book "Hurray, We Capitulate" is a polemic on what he sees as Europe's submission to Islamists. "It's surrender to an enemy you're deathly afraid of.... Europe is like a little dog on his back begging for mercy from a big dog. The driving factor is angst."
Even intellectuals who don't share Broder's views agree that Europe must defend its principles. The change in mood comes as Europeans of all political persuasions are growing less tolerant of Muslim immigrants and questioning whether Islam can coexist with Western ideals.
"We live in Europe, where democracy was based on criticizing religion," said Philippe Val, editor of the French satirical magazine Charlie Hebdo. "If we lose the right to criticize or attack religions in our free countries ... we are doomed."
Europe has been struck repeatedly by Islamic extremists.
In 2004, Madrid's train system was bombed, and a Dutch film director was killed in Amsterdam by a man outraged over a movie criticizing Islam's treatment of women. In 2005, London's transit system was attacked. In the last year, police across Europe have arrested dozens of suspected radicals, including two men accused of planting bombs that failed to detonate on German trains.
Policymakers in capitals including Copenhagen, Paris and Amsterdam are realizing that flawed integration policies have fostered enemies in their midst. Operating within Europe's Muslim population of about 15 million -- the vast majority of whom favor Western-style democracy -- are homegrown Islamic networks linked to Al Qaeda and other terrorist organizations.
Their presence underscores the theological battle between moderate and extremist Muslims. Most Muslims in Denmark protested peacefully against the Muhammad cartoons. Islamic leaders in Germany expressed concern about the Mozart production, but said they would be willing to attend a performance before passing judgment. Government officials and artists were encouraged, but they blamed moderate Muslims for offering only faint public criticism of extremists.
"It's true that moderates in the past were not quoted as much in the media when it comes" to speaking against radicals, said Anas Schakfeh, president of the Islamic Community in Austria. "But this is changing. Moderates do speak up more and more.... We published the names of two or three mosques that have allowed hate speeches. We don't want that."
Leftists argue that Europe is placating radical elements at the expense of its culture, and the continent's image as a bastion of tolerance has clouded the fight against extremism.
When his sculpture was pulled from the Tate exhibit last year, John Lathan accused the gallery of cowardice. "If they want to help the militants, this is the way to do it," he said. "It's not even a gesture as strong as censorship. It's just a loss of nerve."
Hans Neuenfels, director of the German Opera's "Idomeneo," had similar sentiments when the show was canceled: "Where will we end if in the future we allow ourselves, in foresighted obedience, to be artistically blackmailed?"
Perceived slights have in the past inspired threats of violence by Muslim extremists.
Such was the atmosphere that led Pope Benedict XVI to apologize after he quoted a medieval Christian emperor who depicted Islam as "evil and inhuman." Jyllands-Posten, the Danish newspaper that printed the satirical cartoons of Muhammad, including one showing the prophet with a bomb in his turban, also apologized in an effort to defuse violent Muslim protests.