Former colonial powers like France and Britain are not the only European countries suffering from the breakdown of assimilation mechanisms consequent upon mass immigration. The countries of Scandinavia are as well. Given their small populations and generous welfare states, the results are, if anything, even more dramatic.

Consider the case of Sweden. Unlike their neighbours in Denmark, who in 2002 decided to place strict conditions on those wishing to emmigrate to the country, Sweden's political elites have resolutely refused to consider cutting back on migration -- and that despite a foreign born population already at 12%. Worse yet, official multiculturalism effectively rules out assimilation for the constant stream of (mainly Muslim) newcomers. The result is the ghettoization of Swedish cities and an increase in inter-communal violence.

Norwegian blogger Fjordman has documented what this has meant for Malmö, Sweden's third largest city:

According to some estimates, the rapidly growing Muslim immigrant population may turn Malmö into a Muslim majority city within about ten years. It will be the first major Scandinavian city to enjoy this honor, although perhaps not the last. Native Swedes are leaving the city in droves, as crime is rampant and the police publicly admit they don't control all parts of the city. There are now gangs in Malmö specialized in assaulting old people visiting the graves of relatives. Robberies have increased with 50 % in Malmö only during the fall of 2004. The city is descending into general chaos. Fights in the city's movie theatres have become a recurrent problem. Numbers released in January 2005 indicate a sharp rise in the number of rape charges in Malmö. Thomas Anderberg, responsible for statistics at the Malmö Police, says there was a doubling of the number of reported rapes by ambush in 2004, following what was already a decade of steadily increasing numbers of sexual crimes.

What's happening in Sweden should serve as an object lesson for all those countries, the US included, in which a generous immigration policy is accompanied by state-sponsored multiculturalism. And in Sweden, which has long been seen as a model for social democratic governance, the problems posed by contemporary immigration are particularly acute. For as communal relations deteriorate and the social service dependence of unskilled immigrants grows, it is anything but clear how the country is to maintain the consensus on which the post-war providential state was founded.

As Prospect Editor David Goodhart put it in an important 2004 essay:

The diversity, individualism and mobility that characterise developed economies - especially in the era of globalisation - mean that more of our lives is spent among strangers. Ever since the invention of agriculture 10,000 years ago, humans have been used to dealing with people from beyond their own extended kin groups. The difference now in a developed country such as Britain is that we not only live among stranger citizens but we must share with them. We share public services and parts of our income in the welfare state, we share public spaces in towns and cities where we are squashed together on buses, trains and tubes, and we share in a democratic conversation - filtered by the media - about the collective choices we wish to make. All such acts of sharing are more smoothly and generously negotiated if we can take for granted a limited set of common values and assumptions. But as Britain becomes more diverse that common culture is being eroded.

And therein lies one of the central dilemmas of political life in developed societies: sharing and solidarity can conflict with diversity.

Goodhart's dilemma is European in scale. In three weeks, France will be voting on the referendum to the EU Constitution. That the referendum will pass remains uncertain, not least because many voters worry that it will erode workers' rights and the welfare state. The Swedish case suggests that such debates may already be obsolete. With native birthrates collapsing across the Continent and immigration undermining historic solidarities, the postwar welfare state is in serious trouble.

Until Europe comes to terms with these problems, no constitution can save it.