All choice takes place in a world of fact, what philosophers call “hard stubborn fact.” In foreign affairs the facts are of extraordinary dimension, macroscopic in size, infinitely diverse and complex. Centuries of historic tradition, encrusted popular attitudes, diverse levels of civilization, diverse potentialities and rates of economic and political development are apt to be involved. Facts impose limitations upon policy, just as the fact of the money in one's pocketbook imposes limits upon what one can buy. It was his acute awareness of the factual limitations on policy that led Bismarck to define politics as the “art of the possible.“