The concept of national interest is very vague and carries a meaning according to the context in which it is used. As a result it is not possible to give any universally acceptable interpretation of this concept. Hans Morgenthau who has dealt with the concept in his various writings also used the term 'national interest' in different ways and assigned variety of meanings. The use of terms like common Interest and conflicting interest, primary and secondary interest, inchoate interest, community of interests, identical and complementary interests, vital interests, material interests, etc. by Morgerihau in his writings further adds to the confusion.
The problem of defining the concept is also complicated by the fact that researchers have tended to give the definitions of national interest according to the particular approach adopted by them. Frankel divides the various approaches adopted, to define the concept of national interests into two broad categories-objectivist and subjectivist. In the first category he includes all those approaches which view national interest as a concept which can be defined or examined with the help of some definable criteria. In the second one he includes those definitions which seek to interpret national interest as a "constantly changing pluralistic set of subjective references."
The problem of defining the concept is also complicated by the fact that researchers have tended to give the definitions of national interest according to the particular approach adopted by them. Frankel divides the various approaches adopted, to define the concept of national interests into two broad categories-objectivist and subjectivist. In the first category he includes all those approaches which view national interest as a concept which can be defined or examined with the help of some definable criteria. In the second one he includes those definitions which seek to interpret national interest as a "constantly changing pluralistic set of subjective references."