Two determining issues in the evolution of a European Union identity - immigration and Turkish accession - can be traced back to negative perceptions of Islam. Why is Islam seen as a problem? What do we mean when we talk about Islam-related problems?

Many people in Europe see Islam as a problem of great concern. Others feel uncomfortable even linking the words "Islam" and "problem," because they fear stigmatizing a group already seen as vulnerable.

But not articulating the problem means not solving the problem. The ongoing reservation on the part of the Dutch political establishment, for example, is a significant obstacle in tackling issues such as anemic social participation, high school drop-out rates, domestic violence and militant religious fanaticism among people of Muslim background. Dismantling the taboo around this topic is a necessary precondition for ameliorating the societal tensions wracking the Netherlands. A first step toward lifting the taboo is exploring the sources of popular concern with Islam.

The most acute cause of disquiet is fear of pure violence committed in the name of Islam. Terrorism, by definition, aims to spread a sense of insecurity and fear among large groups of people. In this sense, Islamist terrorist groups seem to have succeeded with their attacks in the United States on Sept. 11, 2001, and several others since - in Bali, Casablanca, Madrid and now in London.

Next to the fear of direct violence, there seems to be major concern about Islamic social, religious and political movements throughout Western Europe. These movements operate parallel to the terrorist networks and usually work through dawa, or preachers and missionaries, whose job it is to spread the radical message of political Islam.

There is little doubt that these movements are the primary forces spreading Islamic fundamentalism in Europe today. Generally these organizations have no direct violent agenda themselves, but, as terrorism officials warn, many young Muslim men pass through these groups and find their way to an extremist, militant interpretation of their religion.

Several longer-term concerns are also discernible. First, Islamic education is a source of worry to some. At least some Islamic schools, especially those that operate in close cooperation with nearby mosques, are potential breeding grounds for a large cohort of orthodox anti-Western students.

The ghettoization and Islamification of certain urban areas is also perceived as a disturbing problem. In cities, villages or provinces where Islam is dominant, it may mean that bits and pieces of the Shariah are introduced in practice even though no formal legislation in this direction is taking place.

Large sectors of society are deeply uncomfortable with the gradual emergence of these types of states within the state, where rules and values other than those of tolerant and democratic liberalism dictate social conduct.

Throughout Western Europe, xenophobia forms another basis for the fear of Islam. Although members of traditionally xenophobic groups have often had little contact with Islam, Muslims or immigrants of any kind, they have strongly negative attitudes toward any group with diverging cultural backgrounds or ethnic origins.

The abject ideas of these groups have a paralyzing effect on the discussion of immigration and Islam because established politicians and opinion-makers fear that even slightly touching on the negative elements of immigration and Islam means playing into the hands of the extreme right. But it is clear that not addressing these issues is not only shortsighted but also counterproductive.

Questions about the relationship between Islam and Europe have not been adequately addressed by elites, who fear both Islamic and nativist backlashes. Ignoring the issue, however, leaves a dangerous identity vacuum that encourages fundamentalist intolerance of all stripes.

Democracy requires candid debate, even about sensitive issues. Failure to address European identity and Islam can undermine confidence in the responsiveness of government and perpetuate dangerous democratic and identity deficits that, if unchecked, will weaken the EU at an essential moment in its history.

Ayaan Hirsi Ali is a resident fellow at AEI.