The meanings of power, influence, control, and domination are uncertain, shifting, and overlapping. Although two of these words may be interchangeable in one context, in another context one of the words may refer to a genus and another to a species, or one may refer to a cause and another to an effect. To substitute power for influence would not matter much in the sentence "The United States has very great influence in South American politics," but to interchange them would radically change the meaning of the sentence "Colonel House's power derived not from any constitutional authority but from his influence over President Wilson."

Shifts like this account for much of the intractability of problems associated with power. For instance, power is often said to be a relation (Lasswell 1950, Friedrich 1950, Partridge 1963), yet we talk about the distribution of power, about the power of speech, about seeking power as...