Historians are a danger to the life of nations, says Timothy Garton Ash, quoting Ernest Renan, a 19th century French historian.

He means that by explaining the past, historians can undermine important myths, the kind that hold a country together even more tightly than race, religion, geography or economy. Garton Ash should know. As a historian of the present, professor of European Studies at the University of Oxford and senior fellow at Stanford University’s Hoover Institution, he is an expert in the ways in which national identities crumble, leaving citizens struggling to reconcile yesterday’s myths with today’s news.

In Renan’s time, the vulnerable myth was the French sense of, as he put it, having done great things together and wishing to do more. In Garton Ash’s youth as a graduate student and journalist in East Berlin, when he was known to the Stasi secret police by the code name Romeo (as in Alfa, for his car), it was the moral authority of the surveillance state. Today, one of the most vulnerable political myths, as Garton Ash told a packed concert hall at the University of Toronto, is the inevitability and permanence of Europe.

Europe is nothing of the sort, of course. Like most political projects, it is the result of hard work and good fortune amid the vagaries of history, not destiny. It can be undone. Brexit is a key piece of evidence here. So is Russian aggression on Europe’s eastern fringes, and the increased focus on borders. So is the global wave of nativist identity politics that propelled Donald Trump to power, with counterparts in most European countries, most recently the far right Alternative for Germany, which placed third in last month’s election.

But Europeans seem to believe they are walking the sunny uplands of fateful progress. Like any successful political community, such as the United States, Europe has told an inspiring story about itself as the future, and it takes a cold-eyed expert on the past to set it straight. ...