Bertrand Russell Quote

Instinctively we divide mankind into friends and foes - friends, towards whom we have the morality of co-operation; foes, towards whom we have that of competition. But this division is constantly changing; at one moment a man hates his business competitor, at another, when both are threatened by Socialism or by an external enemy, he suddenly begins to view him as a brother. Always when we pass beyond the limits of the family it is the external enemy which supplies the cohesive force. In times of safety we can afford to hate our neighbour, but in times of danger we must love him.

Authority and the Individual (1949)