Perhaps these French ex-Catholics, while sadly cut loose from their cultural and religious moorings, have gained access to a compensating sophistication? Au contraire. The alternative to Christianity, Mr. Fourquet shows in his book, has not been lucidity; it has been gaga conspiracy-theorizing. A third of French people 18 to 24 years old believe that airplane contrails have been seeded with hazardous chemicals and that the United States military can provoke storms, versus only 7 or 8 percent of those over 65 who believe such things. The decline of religion does not seem to have grounded people in something more true.

That is partly why the fire at Notre-Dame shook so many to the core. Objects and traditions bound up with religious belief lend a feeling of sense and stability. For believers they are a reinforcement. For nonbelievers they are a substitute. Notre-Dame is perhaps the greatest such object in Europe. It is a consoling relic, as surely as the crown of thorns that Father Fournier rescued, and this is so for believers and nonbelievers alike.

The cathedrals, for all their sacred origins, call to mind a worldly folk saying: The first half of your life, you work for your name; the second half of your life, your name works for you. Over centuries France constructed its monuments. Now monuments construct France.