It is hard for people not to see the world in polarizing terms ("them" and us") and these terms have in the past strengthened the isolationist theme in American foreign policy as much as they now strengthen the imperialist theme. Americans have got used to thinking of the world in terms of enemies. Enemies are somewhere else, as the fighting is almost always "over there," with Islamic fundamentalism now replacing Russian and Chinese communism as the implacable, furtive menace to "our way of life." And terrorist is a more flexible word than communist. It can unify a larger number of quite different struggles and interests.