An ethnic group is a group of people who identifiy with one another, or are so identified by others, on the basis of either presumed cultural or biological similarities, or both. Like race and nation, the notion of ethnicity developed in the context of European colonial expansion, when mercantilism and capitalism were promoting global movements of populations at the same time that state boundaries were being more clearly and rigidly defined. In the nineteenth century, modern states generally sought legitimacy through their claim to represent "nations." Nation-states, however, invariably include indigenous populations that were excluded from the nation-building project, or recruit laborers from outside their borders; such people typically constitute ethnic groups. Members of ethnic groups, consequently, often understand their own identity in terms of something outside of the history of the nation-state -- either an alternate history, or in ahistorical terms, or in terms of a connection to another nation-state. Such identity often expresses itself through various "traditions" which, although often of recent invention, appeal to some notion of the past.
Sometimes ethnic groups are subject to prejudicial attitudes and actions by the state or its constituents. In the twentieth century, people began to argue that conflicts among ethnic groups or between members of an ethnic group and the state can and should be resolved in one of two ways. Some, like Jurgen Habermas and Bruce Barry, have argued that the legitimacy of modern states must be based on a notion of political rights of autonomous individual subjects. According to this view the state ought not to acknowledge ethnic, national or racial identity and should instead enforce political and legal equality of all individuals. Others, like Charles Taylor and William Kymlicka have argued that the notion of the autonomous individual is itself a cultural construct, and that it is neither possible nor right to treat people as authonomous individuals. According to this view, states must recognize ethnic identity and develop processes through which the particular needs of ethnic groups can be accommodated within the boundaries of the nation-state.