The study of internationl relations takes a wide range of theoretical approaches. Som emerge frim within the duscipline itself others have been importen in whole or in part from disciplines such as economics or sociology. Indeed few social scientific theories have not been applied to the study of relations amongst nations. Many theories of international relations are internally and externally contested and few scholars believe ohly in one or another. In spite of this diversity several major schools of thought are discernable differentiated principally by the variables they emphasize military power material interests or ideological beliefs