A generation ago it would have been inconceivable that the French legislature should expressly forbid Muslim dress in schools, or that this issue should throw the nation into crisis.

The principle of laïcité, which removes religion from all state educational institutions, while covertly making room for the old Catholic culture of France, had been entrenched since Napoleonic times. State schools were in the business of producing French citizens, and citizenship was supposed to make no reference to religion, but only to the nation and the state of France.

A generation ago it would have been equally inconceivable that anti-semitism should be rife in France, or that it should display itself in the desecration of Jewish cemeteries and the burning of synagogues. And had these crimes been committed by some immigrant community, the police would have openly said so and would not have referred to a national rather than an ethnic disorder, as they are now obliged to do.

Yet those who commit these crimes are contemptuous of their assumed nationality, and define their loyalty in opposition to the surrounding secular culture. The new anti-semitism is not a French phenomenon at all.

A generation ago it would have been equally inconceivable that a distinguished French novelist should have been put on trial for describing Islam as a stupid religion, that he should have come close to being jailed for religious incitement and that he should feel advised, on being acquitted, to emigrate to Ireland. Yet such is the case of Michel Houellebecq, author of the much praised novel Atomised, who remains one of the few public voices who will not bow to the prevailing censorship.

The French story could be told of the other nation states of Europe. The secular order of the nation state is under threat. Freedom of speech is disappearing and the ordinary citizens of European states are deeply anxious about the long-term consequences.

Nationhood was the great European achievement, the social fact that made Enlightenment possible, and which underpins the secular rule of law. Thanks to national loyalty it has been possible for people to accept a common allegiance and a shared sense of community, and put old ethnic and religious conflicts behind them.

It is not only Europeans who appreciate this fact. Never in the history of the world have there been so many migrants. And almost all of them are migrating from regions where nationality is weak or non-existent, to the established nation states of the West. They are not migrating because they have discovered some previously dormant feeling of love or loyalty towards the nations in whose territory they seek a home. They are migrating in search of citizenship — the relation that arises between the state and the individual when each is fully accountable to the other.

Citizenship consists of a web of reciprocal rights and duties, upheld by a rule of law which stands higher than either party. Although the state enforces the law, it enforces it equally against itself and the citizen. The citizen has rights which the state is duty-bound to uphold, and also duties which the state has a right to enforce. Because these rights and duties are defined and limited by the law, citizens have a clear conception of where their freedoms end.

Only where people define their social membership in terms of sovereign territory, shared customs and a common history — in other words, the nation — are they able to live in a democratic, law-abiding order. In a nation state people can agree to differ; they can accept being governed by those for whom they did not vote; they can agree equal rights for all religions; they can allow their opponents to speak their minds and influence the political process. But where religion, tribe or family is the dominant form of social membership, despotism is also the political norm.

That is why 70% of the world’s refugees are Muslims, fleeing from states where their religion is the official creed. And it is why all of them are fleeing to the West.

However, while the newcomers seek the benefits of citizenship, they do not always accept the costs. The primary cost is the privatisation of religion and the public endorsement of the secular rule of law. The secondary cost is tolerance, which means living with free speech, alien manners, other religions and other tribes, Jews included.

Democracy also means living with strangers on terms that may be, in the short term, disadvantageous; it means being prepared to fight battles and suffer losses on behalf of people whom you neither know nor particularly want to know. It means appropriating the policies that are made in your name and endorsing them as “ours”, even when you disagree with them.