The French law of separation between church and state is one of the most concrete steps in the development of French secularism (“laïcité”), which remains a defining characteristic of the country today. During the French Revolution of 1789, the rise of secularism spurred a “de-Christianization” (“dechristianisation”), leading to a decrease in the power and omnipresence of the Catholic Church in society. With Napoleon's seizure of power in 1799, many old traditions were upset: both the shift from Monarchy to Empire and Napoleon’s symbolic coronation ceremony (in which he crowned himself in lieu of the Pope doing so) created a perception of the State as equal to the Church. Lastly, Napoleon’s Concordat agreement of 1801 with the Vatican was not well-received in his Catholic country, a reaction that helped lay the path to the secular society that would take hold, and still persists today.

Another large contributor to the rise in secularity and in anti-Catholic sentiments was the increase in publicly educated citizens. Long after Napoleon I, during the “guerre scolaire” (school war) of the 1870s, the French state began to build free, secular public schools to compete with the country’s traditional Catholic schools. In 1881, the Ferry laws, named for the prime minister of the time, required school for all children, forcing poorer children who would otherwise have been in the labor force to attend public, secular schools. Moreover, by encouraging the education of girls in public schools, the government began to shape mothers, families, and citizens without religion. Then, in 1894, the Dreyfus Affair completely disrupted the Third Republic, polarizing a society which was already cracking in two. After the intense media coverage of the Dreyfus Affair, and thanks to the very high rates of literacy and education of that time, “popular front secularism” began: a widespread anticlericalism. Criticisms of luxury and lust in the Church, and suspicions that it was corrupt, spread throughout society with the help of yellow journalism and an increasingly educated population. Because of these scandals, Protestants began to push for a smaller and poorer Catholic Church.

By the early 1900s, French society was nearing the end of a long-anticipated change. Many public officials realized that the damaged relations between the Church and the State were irreversible and pushed for a complete “divorce” of the two entities. Progressives were generally in favor of the separation, with support from anti-monarchists (known as Republicans) varying, and little support from Catholics. The main principle leading to the law’s passage was that it allowed religion to continue to be exercised without interruption. After about four years of Senate and lower house negotiations, the famous 1905 law, the Separation of Church and State, was enacted.

Its first article emphasizes that the Republic “guarantees the free exercise of worship,” ensuring that religions are not prohibited in France. The second article, the most important one in terms of change, says the “Republic does not recognize, does not pay, nor does not subsidize any worship.” This revolutionary article forced the Church to become a smaller and less powerful entity due to diminished financial resources. It also broke Napoleon’s Concordat agreement of 1801, which declared Catholicism the majority religion of France and guaranteed state support of the Church.

After the law’s passage, some Catholics said “acceptance of the separation would be a humiliating capitulation,” and that because the Concordat was an agreement between two entities, one must consult the other before it could be nullified. Of course, the friendly relations between the Vatican and France were also disturbed: Pope Pius X condemned the rupture, saying it was not compatible with the Church. Others raised the possibility of the law's harmful effects on the Republic by giving the Church total freedom of maneuver.

An interesting exception to the law of separation is the region of Alsace-Moselle, which was under German control in 1905. When it returned to France in 1919, it kept its German laws and did not adopt the principle of secularism. And even today, it is not a secular region like the rest of France: the government of Alsace pays the salaries of its ministers of worship. The situation in Alsace is a subject of debate and controversy now, because it is in direct contradiction to the concept of secularism and the law of 1905.

Even in the rest of France, the law of 1905 is frequently challenged, in particular on its compatibility with Islam, the second-most practiced religion in France. The law prohibits any demonstration of religious affiliation in public schools, including wearing a cross necklace or a hijab. It has been criticized for unfairly targeting members of the Muslim community, as their religious practice of wearing a hijab is much more evident than those of Christians, whose religious symbols do not stand out as readily. Though the law has been amended several times since its inception, the original principles of its second article have not been changed. Secularism is a deep-seated concept in French history, and any monumental changes to the law, if they ever occur, will spur controversy and uprising among its devout supporters.