For most of the twentieth century, social thinkers devoted their attention mainly to the issues of economic class. They generally dismissed the more primordial bonds of racial, ethnic, and national identities as irrational anachronisms that either communism or the liberal frameworks of democracy would dissolve.

Today, communism is nearly dead and liberalism is on the wane. At the same time, older ethno-racial tribalisms, along with some newly invented ones, have shattered our illusions of a rationally manageable world. They find expression in chauvinistic nationalisms,...