Intergroup antagonism is thus the inevitable concomitant and counterpart of in-group solidarity

From Social Structure by George Peter Murdock.

Under conditions of relative isolation, each community has a culture of its own. The degree to which this is shared by neighboring local groups depends largely upon the means and extent of intercommunication. Ease of communication and geographical mobility may produce considerable cultural similarity over wide areas, as, for example, in the United States today, and may even generate important social cleavages which cut across local groupings, as in the case of social classes. For most of the peoples of the earth, however, the community has been both the primary unit of social participation and the distinctive culture-bearing group.

United by reciprocal relationships and bound by a common culture, the members of a community form an "in-group," characterized by internal peace, law, order, and cooperative effort. Since they assist one another in the activities which gratify basic drives, and provide one another with certain derivative satisfactions obtainable only in social life, there develops among them a collective sentiment of group solidarity and loyalty, which has been variously termed syngenism, we-feeling, esprit de corps, and consciousness of kind.

Social life, despite the manifold advantages and rewards which reinforce it, also involves incidental frustrations. The individual must curb certain of his impulses if he is to secure the cooperation of his fellows, and when he fails to do so he experiences the application of painful social sanctions. These frustrations, as always, generate aggressive tendencies. The latter cannot, however, be fully expressed within the in-group, Test mutual aid be withdrawn and further sanctions imposed. Consequently they are displaced toward the outside and drained off in the form of antagonistic sentiments and hostile behavior toward other groups. Intergroup antagonism is thus the inevitable concomitant and counterpart of in-group solidarity.

The tendency to exalt the in-group and to depreciate other groups, a phenomenon technically known as "ethnocentrism,"
though perhaps originally associated primarily with the community, has, with broadening social horizons, become characteristic of all human social groups. Today, for example, it runs the gamut from "local pride," "college spirit," and the esprit de corps of a business organization to religious intolerance, race prejudice, the "class struggle," and international conflict. However deplorable from an ethical point of view, it is as inevitable as social life itself; at best it is capable only of being directed into channels that are socially less seriously disruptive.