There is, it must be confessed, a psychological difficulty about a single world government. The chief source of social cohesion in the past, I repeat, has been war: the passions that inspire a feeling of unity are hate and fear. These depend upon the existence of an enemy, actual or potential. It seems to follow that a world government could only be kept in being by force, not by the spontaneous loyalty that now inspires a nation at war. - Bertrand Russell