At any given time during the past decade, several ethnic conflicts have raged around the world. In the year 2001, these include such well-known cases as Kosovo, Chechnya, Israel, Kashmir, Sri Lanka, and Indonesia. In the view of many political analysts and social scientists, the era of the Cold War and ideological conflict has given way to an era of ethnic wars and cultural conflicts. Whether one subscribes to this characterization or another (one of the most convincing is that this is the era of globalization), ethnic conflict is an undeniable feature of the contemporary sociopolitical landscape. 
What is its cause? The problem with answering that question is not the lack of theories, but rather an excess. Around the question of ethnic conflict has sprouted a plethora of answers, a thicket of theories suggesting variously that (1) cultural traditions and historical legacies are giving rise to "primordial hatreds"; (2) the socioeconomic tensions produced by modernization and uneven development stoke violence among ethnic groups; and (3) political disorder and "failed states" create a "security dilemma" between ethnic groups that are often exploited by ambitious and unscrupulous "political entrepreneurs.
In each of these three major theories, religion occupies a crucial position. This is most obviously the case with the cultural explanation, in which the principal content of the historical legacy and primordial hatreds is perceived to be religious tradition and memories of past religious conflicts. It is also the case with the socioeconomic explanation, in which the strains of modernization are said to produce a revival of religion, even an "invention of tradition," in order to give people some stable meaning within the turmoil of socioeconomic change. And it is also the case with the political explanation, according to which people seek refuge from the security dilemma in the ruins of failed states by fleeing into the protection of a religious community.
The idea that religion plays a crucial role in ethnic conflict has been attractive to many social scientists, since their personal beliefs have often made them predisposed to be hostile toward religion. If religion can be shown to be a necessary or sufficient cause for ethnic conflict, then that is all the more reason why it would be best if the role of religion in any society (including the United States) declined and even disappeared. Religion certainly seems to have been present in a wide range of ethnic conflicts in the past decade. These include Northern Ireland, Yugoslavia, Egypt, Sudan, Israel, Lebanon, Chechnya, India/Pakistan, Sri Lanka, Indonesia, and the Philippines. Together, these would seem to provide overwhelming evidence that ethnic conflict is caused or at least exacerbated by religion. However, in the case of the most murderous ethnic conflict of all in the 1990s, that of Rwanda, there were no religious differences at all between the Hutu and the Tutsi.
Discerning the pervasive presence of religion in a wide range of ethnic conflicts does not establish religion as the best explanation for those conflicts. Just because a factor (in this case religion) is present in a particular case does not necessarily mean that it is predominant or even prominent. Other factors may be equally pervasive or more prominent. Socioeconomic differences between ethnic groups alone would certainly provide a good explanation for almost all of the ethnic conflicts listed above. Political change and consequent turmoil also would seem to account for several of the most extensive and violent cases, including Yugoslavia, Chechnya, and Indonesia.
The A Priori and A Posteriori Fallacies
The weakness in using religion to explain ethnic conflict is illustrated by two classical problems in explaining social phenomena: a priori underdetermination and a posteriori overdetermination.
The problem of a priori underdetermination means that, before the fact of a social phenomenon or event, it is rarely possible even for experts to predict with any accuracy that it will occur. For example, as late as 1989 no expert on Yugoslavia was able to foresee the horrendous ethnic conflict that began to unfold in 1991. Even those analysts who devoted their attention to religious differences were surprised by what happened. Conversely, if one were looking at the ethnic tensions in the Baltic republics of the Soviet Union in 1989, one could have easily predicted serious ethnic violence. This would have been especially so if one focused upon the religious differences. Yet although there were persistent ethnic tensions in these countries throughout the 1990s, almost no ethnic violence ever occurred. More generally, the presence of different religions, even different religious communities, in a society does not by itself help us to predict accurately an ethnic conflict before the fact. A priori, the conflict is underdetermined, even with the presence of religion as a factor.
Conversely, the problem of a posteriori overdetermination means that, after the fact of a social phenomenon or event, it is always possible to find not just one factor, but several, each of which might be used to construct an explanation for why that event occurred. Indeed, it even seems possible to demonstrate that the event had to occur, that it was inevitable. For example, experts on Yugoslavia wrote numerous books in the 1990s purporting to show that the ethnic wars there were readily explained by such factors as religious traditions, socioeconomic tensions, political breakdown, or some combination of them. The other ethnic conflicts mentioned above have, after the fact, been similarly explained.  More generally, the presence of different religions, especially different religious communities, in a society can always be used to explain an ethnic conflict after the fact. But this is often equally true of other factors. A posteriori, the conflict is overdetermined, not only by the presence of religion, b ut by the presence of several other factors as well.
Some social scientists believe that these explanatory problems can be solved through a version of the comparative method by …