"THE EXPLOSION OF communal violence is the paramount issue facing the human rights movement today. And containing the abuses committed in the name of ethnic or religious groups will be our foremost challenge for years to come." This is the blunt assessment of the acting executive director of Human Rights Watch, a global monitoring group based in New York. There are currently between seven thousand and eight thousand linguistic, ethnic, or religious minorities in the world's 191 nations, fewer than 10 percent of which are ethnically or racially homogeneous. Only half of the countries with populations of over one million have a single ethnic group accounting for more than three-quarters of the population. Multiethnic states in Europe, Asia, Africa, and the Americas face the challenges of cooperation and conflict resolution. Amidst these attempts to unify, however, a growing number of politicians have tried to exploit ethnic differences to build followings...