There is something tragic about Europe's current development. Democracy's march across the continent, and the formation of a single market across much of Europe, have created unprecedented stability, security, and prosperity. The new single currency, the euro, and the European Union's promise to admit as many as ten new members in 2004, are powerful indicators of ongoing integration.

Yet, the ability of European institutions to accommodate deeper and broader integration is increasingly undermined by the persistence of a contradictory and long-obsolete ideal: the nation-state as the basis of political legitimacy and sovereignty. It is largely because the idea of common European citizenship is often understood by analogy to that of national citizenship that further European integration engenders so much fear and opposition.

The nation-state in the traditional sense presupposed a citizenry that was created as competing collective identities decayed. Venetians became Italians, Bavarians became Germans, and so on. Nation-builders throughout Europe promoted - with varying degrees of success, to be sure - the emergence of a dominant culture, an official language, and an identity based partly on distinctions vis-à-vis neighboring states, peoples and cultures. National minorities everywhere faced expulsion or enormous official pressure to assimilate.

A European nation-state in this sense was untenable even for the original six members of the European Community - all of them highly industrialized countries with similar social and political traditions and institutions. It is no more feasible today for the EU's 15 members, and further enlargement means that the multitude of collective identities, cultures, languages, religions, and worldviews will become greater still. The singular "people" that defines citizenship in a traditional nation-state could be forged only by plunging Europe into appalling repression and war lasting generations, if not centuries.

Of course, European integration has been driven from the outset precisely by the shared historical memory of the terrible suffering wrought by aggressive nationalism. But without an alternative to the nation-state as the basis of citizenship, the legitimacy and effectiveness of EU institutions have come under growing strain.

Witness, for example, Ireland's veto of the institutional reforms adopted at the EU's Nice summit in December 2000 - reforms without which enlargement cannot go forward. Similarly, opinion polls show that support for EU membership has fallen rapidly even in many candidate countries. Political leaders such as Vaclav Klaus in the Czech Republic and Viktor Orban in Hungary welcome the common market, but argue that their nation-states did not re-gain their de facto sovereignty from Moscow only to surrender it de jure to Brussels.

Yet free movement of goods and services, labor, capital, and ideas (the single market's "four freedoms") makes irrelevant much of what traditional European nation-states do - namely, defending these freedoms within a smaller territory. With the EU's internal borders reduced to purely administrative boundaries, this task has passed to institutions that wield immense preemptive authority over member states. An alternative must therefore be found to a definition of citizenship that regards these institutions as merely some sort of formalized representation of member states' common political will.

What should an alternative conception of European citizenship look like? The US model of political identity, shaped by a legacy of immigration and voluntary cultural integration, cannot be simply transposed to Europe, where distinct traditions, cultures, and attitudes are so deeply entrenched. But a conception of citizenship that is basic and minimal is essential where a Pole and a Swede may fall in love while studying in Spain, begin their careers in Germany, and settle down to raise a family in Italy. Common citizenship does not require a common form of life, common existential values or a common historical past.

Indeed, this is the only democratic and stable definition of European citizenship, because it alone is capable of eliciting the consent and allegiance of every individual. Clearly, people in the real world do not ordinarily get to choose the basic structure of their society. But imagine, in the spirit of the philosopher John Rawls's famous thought experiment in his book A Theory of Justice , that you do get to choose the rules - although without knowing who you will be in such a hypothetical society.

Assuming that you are rational, you must calculate that you may be a member of a cultural minority. Obviously, you will not choose rules that define citizenship in terms of a particular cultural identity. On the contrary, you will seek to hedge your bets by ensuring that citizenship is constituted by individual rights of participation in collective projects, backed up by a legal system that guarantees these rights.

Citizenship in this sense views political sovereignty and legitimacy as features of institutions that foster voluntary social cooperation by embodying rules of interaction that are viewed as fair and efficient from the perspective of everyone. If repression were enough to secure compliance with the rules, democratic legitimacy would be unimportant. As the collapse of communism in Eastern Europe demonstrates, repression alone is a poor guarantee of stability.

European citizenship understood in this way is compatible with a multitude of collective identities ranging from family or friendship groups to professional associations and corporations, regionally defined communities, and shared cultural, political and religious affinities. Such a conception stabilizes social cooperation within Europe because it reflects a basic normative consensus on the design of institutions and thus orients individual behavior toward preserving these institutions.

In fact, a well-developed conception of democratic citizenship will always emphasize individual rights. Citizenship is not constituted by groups, but by individuals interacting as citizens with specific interests and goals. This means that they pursue their interests and goals within commonly accepted rules of interaction including, naturally, rules of conflict resolution between different collective identities.