But now Europe asks for sacrifices and solidarity, and it finds itself on the decline. Everywhere, populists and nationalists gain. Managing austerity, fighting debt — this, it turns out, is no way to unite Europe.

Perhaps Europe’s leaders should have been more alarmed when enthusiasm for unity began fraying even before the crisis. In 2005, French and Dutch voters blocked progress toward a European constitution. Meanwhile, the newly free countries of Central and Eastern Europe — Milan Kundera’s “kidnapped West,” disfigured by 45 years of Soviet occupation — hadn’t so much re-Europanized their economies as globalized them. The same is true of Europe’s rising generation; it knows the pleasures of a modern economy. But those are available globally to anyone with their level of wealth and privilege. Apart from that euro in their pockets, Europe’s young people do not feel Europe’s presence on a daily basis.