A century ago, France pulled down the crucifixes hanging in its classrooms in a triumphant climax to its fight to separate the state from the powerful Roman Catholic Church.
Today, battle lines are being drawn over another religious emblem, the Islamic head scarf, which some French see as a threat to their nation's core values and unity.
A bitter debate over whether the head-covering can be worn in public schools, or by civil servants, has festered for nearly 15 years and deepened as France's Muslim sons and daughters come of age.
Some see it as a flag of Islamic militancy, or a sign of submission to men. Others see it as the start of a spiral into unknown territory that could transform France's definition of itself.
With 5 million Muslims, more than 8 percent of the population and increasingly assertive, France is becoming concerned for its hard-won secular underpinnings — guaranteed by the constitution.
So deep are these concerns that President Jacques Chirac established a commission in July to study just where secularism stands in a country with the largest Muslim population in Europe.
"It is indeed the question of our national cohesion that is being posed," Chirac said in July. "We cannot remain passive."
Prime Minister Jean-Pierre Raffarin has threatened that if necessary he'll pass a law to impose secularism. "I'm not afraid of Islam," he said last spring.
The issue isn't just the humble head scarf. Both Chirac and the prime minister have voiced disapproval over other Muslim demands that they see as challenging basic tenets of what it is to be French: sexually segregated classrooms, a school calendar that respects Muslim holy days and the refusal to take oral exams with professors of the opposite sex.
But it is the scarf that has captured center stage.
The level of debate racheted up with the expulsion this month of two sisters from the Henry Wallon high school in Aubervilliers, a Paris suburb, for refusing to remove their scarves.
"They were chased out of school like dogs," said Laurent Levy, father of Lila, 18, and Alma, 16. He claimed fear of Islam is "eating away at French society."
Teachers said the school acted on complaints from some Muslim pupils who wanted the ban enforced.
Interior Minister Nicolas Sarkozy backed the expulsion, and Francois Hollande, leader of the opposition Socialist Party, agreed, saying: "The law must be applied. We're in a secular country."
Each year, there are about 150 complaints involving head scarves, according to Hanifa Cherifi, the Education Ministry's mediator who intervenes in crisis situations. Unresolved cases lead to expulsion — fewer than 50 last year, Cherifi said.
Even among Muslims there is disagreement over whether their religion mandates the scarf that in most cases covers hair, ears and sometimes forehead and shoulders. But hundreds of girls defy the unwritten code forbidding scarves in public schools. While many schools tolerate it, it leads to conflicts, teachers' strikes and court cases in others.
There are large Muslim communities in neighboring countries, from Britain to Belgium. Incidents involving scarves are usually settled quietly on the local level, but in September, Germany's highest court failed to resolve the case of a Muslim woman who was denied a state teaching job unless she doffed her scarf.
The court asked Germany's 16 states to draft laws on scarves in state institutions, and four of them quickly announced they would seek to legislate a ban.
"The head scarf, after all, is not just folklore and a mere symbol (but) a demonstration of an expression of faith," said Hesse state minister for schools, Karin Wolff.
The Council of State, France's highest administrative body, has said scarves should be banned only when they are of an "ostentatious character." It left schools to make that judgment case by case.
The same rules apply to Jewish skullcaps and Catholic crucifixes. But there have been no public incidents triggered by students insisting on wearing skullcaps or "ostentatious" crosses. There are many private Jewish schools in France, where skullcaps can be worn, but only two such Muslim schools.
In July, a Lyon court ruled against a civil servant suspended for refusing to remove her scarf at work. A month earlier, a Paris appeals court upheld a decision in favor of a woman who lost a private sector job after refusing to shed her scarf. Paris City Hall is debating whether to suspend a city social worker who refuses to remove her scarf or shake the hand of men she meets on the job.
"We're in a sort of circle, like a serpent biting its tail," said Sylvie Taleb, principal of the Averroes Lycee, France's first Muslim high school, located in a mosque in the northern city of Lille. Taleb, who teaches French, is a convert from Catholicism and wears a head scarf.
Many women say it's an inseparable part of their identity.
"It's practically my arm, my foot," said Fatima Ezahoui, a 37-year-old mother of four living in Villepinte, north of Paris. "It's part of me."
She dismisses the debate as a "false problem."
"It's like the young girls and their head scarves will destabilize the country," she said. "Is France that fragile?"
France redefined itself in 1905 with a law separating church and state. Crosses were even forbidden on coffins during funeral processions, said Michele Tribalat, a sociologist. Rancor evolved into separate but peaceful coexistence.
The increase in Muslim girls insisting on wearing scarves to school parallels a rise in Muslim fundamentalism over the past 15 years, and a general increase in demands by minorities.
"Today, Islam is seen and shows itself, and that stirs fears," said Franck Fregosi, an expert at the National Center for Scientific Research.
France has for centuries fully assimilated its diverse population, which adopts French values whatever their origins. It is a model directly opposed to the Anglo-Saxon melting pot.
"We're not completely sure of ourselves in this matter because our model is coming apart before our eyes," said Tribalat, the sociologist.