Realist theory claims that nations are motivated by considerations of power. In this impressive book, Mark L. Haas contends that ideology has played a far greater role in shaping politics among major states over the last two centuries than realism expects. Searching for a systematic impact, Haas argues that the degree of ideological 'distance' between great powers has been crucial in how their leaders define interests and perceive threats. It is not the content of a state's ideology—defined as its prevailing political principles—that matters so much as it is the ideological affinities or differences between states. Haas expects that, like birds of a feather, similar sorts of states, regardless of whether they are liberal, monarchist, communist, or fascist, will tend to flock together. Haas is most convincing in showing that power and ideology operate together in shaping perceptions of threats and interests.(Foreign Affairs) This is a definite must-read. Haas is an effective writer; each of the case studies is meticulously researched, and the evidence marshaled in support of the hypotheses is impressive. Overall, he makes a strong case for the inclusion of ideological factors, specifically distance, in examining and predicting the behavior of leaders of nation-states toward each other.(Perspectives in Politics)