So it is difficult for governments who learned to urge calm on their populations in times of terrorism to now learn how to frighten them into acting for the common good.

During the great Black Death of the 14th century, which took so many lives, people believed that God had condemned those who died and chose whom to spare. But in a secular society “it’s harder to find the morality in who is dying,” Mr. Krastev said. “Instead you have all these conspiracy theories,” with talk of the “foreign virus” and even a Chinese spokesman suggesting that the American military was to blame.

In 2003, George Steiner, the European philosopher who died last month at 90, wrote a famous essay for the Nexus Institute called “The Idea of Europe.” But that idea is under threat.

Europe’s cultural identity, Mr. Steiner wrote, is founded on several characteristics largely missing in the United States, where car culture, suburban sprawl and great open spaces engender a sense of separateness.

In Europe, it is a culture of coffee houses and cafes, where people meet, read, write and plot. They are places, Mr. Steiner said, “for assignation and conspiracy, for intellectual debate and gossip, for the flâneur and the poet or metaphysician at his notebook,” open to all.

Europe’s is also a pedestrian culture, founded on squares and small streets, usually named after scholars and statesmen, famous for their works and their massacres. Europe “is walked,” he wrote, and “distances are on a human scale.”