A century ago, Europe's pretensions fitted the realities of its influence better than they do today. It made some sense for a continent that ruled vast colonial empires on a shoestring to claim to be the centre of the world, or "history's heartland". The "rest of the world" - a magnificently parochial category that still shapes the world-view of some of our oldest universities - was at the periphery; Europe was essential, the core of civilisation.
If such a picture was ever really true, it is certainly changing now: the free-trade tide has reversed course with a vengeance, and swathes of Europe's surviving textile industry have been submerged beneath the wave of Chinese competition. The continent's dependence on central Asian oil and gas is growing fast, and militarily it has not been in charge of its own destiny since 1945 (a state of affairs that the end of the cold war did little to change). And with the continent's populations ageing and drawing the line at 1.3 children, it seems likely that only a continued - indeed, accelerated - influx of migrant workers from Africa and Asia will prevent its pensions gap from bankrupting state budgets and private households.
Yet this dramatic scaling down of Europe's place in the global balance of power has coincided with many considerable achievements, including the pacification since 1950 of virtually the whole of a continent that once led the way in internecine warfare; the restructuring of the welfare state; and the consolidation and rescue of parliamentary democracy. Are these achievements as fragile as the continent's current mood of introspective defensiveness suggests, and what kind of Europe have they actually produced?
Tony Judt's Postwar, an extended rumination on Europe's transformation over the past half-century, prompts such questions and helps suggest some answers. Judt is an omniscient, judicious guide, whose fluent style is here combined with deep knowledge. His own wide interests - in the intellectual history and culture wars of the French left, in the politics of postwar reconstruction, and in the collapse of communism in eastern Europe - have shaped an interpretation that anyone interested in Europe's future will have to take seriously, while his extensive involvement over many years in building bridges between historians either side of the Iron Curtain allows him, unusually, to take in Europe as a whole.
In the aftermath of Germany's defeat, many Europeans believed that the continent had lost control of its destiny. They told a story of two halves, one Americanised (in most versions for the better), the other gripped by Soviet tyranny. American hegemony made possible the miracle of growth and political co-operation in the western half, which became the kernel of a new European Community; Moscow, on the other hand, took what it could, ruled through the tank when other means failed, and brought freedom to the east only when its own system collapsed.
Judt shows us, however, that things were not so simple. In both east and west, nation states buckled but did not collapse. Ernest Bevin and Georges Bidault were as much the architects of the Marshall Plan as any Washington policy-maker, while to the east Tito, Wladyslaw Gomulka and Gheorghe Gheorghiu-Dej reminded Moscow that their states had not been incorporated into the USSR (unlike, say, the Baltic republics) and retained some room for manoeuvre. Another way of putting this is that the postwar period looks less like the era of the collapse of the European nation-state system than like another chapter in its history.
If we wanted to be heretical, we might go further and say that in some respects the postwar division of Europe mattered less than it seemed. It certainly mattered for civil liberties, and for freedom of movement and expression. The two halves of the continent also shared a great deal, however. School and university systems expanded fast in both, as did public healthcare networks. It is sometimes hard to tell the difference between a Greek and a Bulgarian postwar government building or state-run hotel - the International Style fitted both countries. Bureaucrats and technicians on both sides were forced to cope with similar problems: of traffic control, noise prevention, pollution. Postwar growth turned peasants into city-dwellers (if not workers) in France and Romania, the only difference being that because France - like the rest of western Europe - had fewer peasants than Romania, it had to look outside Europe for its labour needs. Growth itself was as fast initially, maybe faster, in the east, but turned out to be more sustainable in the west, and better able politically to cope with global competition in the 1980s.
Judt is especially illuminating on Europe's postwar culture wars. Living in the great ideological incubator of the century, the continent's intellectuals debated the legacies of Hitler and Stalin, forgot what was expedient and settled old scores whenever the opportunities presented themselves, with a helping hand from both their US and Russian associates. What emerges very forcibly from this account is how poorly their obsession with the past equipped them for dealing with the very different issues facing the continent after 1990. Was communism worse than fascism? Was Ion Antonescu a patriot or a collaborator? Were wartime killings of civilians the fault of the Germans or of the partisans who provoked them? Such questions have many possible answers, but none is of much help in thinking through how to adjust expectations of cultural belonging and citizenship to accommodate the relatively new immigrant populations that have now also made the continent their own.
Western Europe needs to devote some of the same energy that went into the transformation of welfare policies after 1945 to reforming ossified and self-congratulatory models of secularism, which are more suited to 20th- and even 19th-century realities than to the present. And as Judt eloquently suggests, placing the Holocaust at the heart of contemporary European identity gets in the way of understanding Germany's transformed role in the continent (something the British find particularly hard to keep in mind); it also offers a dubious yardstick by which to evaluate present-day racism.
Judt ends by suggesting (and there are hints here of the disillusionment of a close observer of Bush's America) that Europe may still be available as a kind of social-democratic model for the world, an alternative to more inegalitarian forms of capitalism. However, I read the book primarily as a wake-up call, reminding Europeans of a period in which they responded to a self-inflicted catastrophe by forming new alliances, restructuring institutions and adopting long-term solutions. Is it necessary to have a war to generate such energy? If Iraq is anything to go by, it is certainly not sufficient. Both within the parameters of the European Union and outside it, Europe needs to learn from its past and put its history behind it. Its postwar achievements were real, but they, too, now need to be judged in the light of present needs.
That war between France and Germany is unthinkable is, in many ways, the great achievement of the European project. The new challenges are not greater, but they are very different and involve Europe's relations with Turkey, North Africa and east Asia. Will it even be possible to write a stand-alone history of 21st-century Europe? It will certainly be hard to do so as elegantly as Judt has done.
Mark Mazower teaches history at Columbia University. His most recent book is Salonica, City of Ghosts: Christians, Muslims and Jews 1430-1950 (Perennial)