Tolerance, once something of an awkward supplement to liberalism, reemerged at liberalism's center in the late twentieth century. In nations and regions saturated with "difference"- ethnic, racial, religious, sexual - tolerance has been promulgated as an individual virtue, a group ethos, and a state policy. It is advocated for situations as disparate as war-torn Bosnia, racially diverse elementary schools in the United States, and European nations coping with recent waves of African and Asian immigration.