A majestic survey of the West's principal schools of sociopolitical thought. In making an (at least tacit) appeal for theoretic pluralism, Princeton political scientist Doyle focuses on three intellectual traditions: realism, liberalism, and socialism. While doing so, he provides perceptive perspectives on the worldviews of important thinkers down through the ages. To probe the canons of realism, for example, the author assesses Thucydides and a trio of latter-day counterparts (Hobbes, Machiavelli, Rousseau). Likewise, he draws on Bentham, Kant, Locke, Schumpeter, and Smith (as in Adam) to illustrate the breadth and depth of international liberalism. Last but not least, Doyle examines socialism through the minds of Lenin and Marx. He reviews the way in which each theory enjoys a comparative advantage in explaining historic events and foreign policies, e.g., the tendency of liberal states to engage in aggression against less enlightened or more authoritarian regimes. The author goes on to appraise what direction the three constructs might offer on some of the world's knottier problems, inter alia, the issue of interventions in the name of human rights as well as other putatively just causes, and whether economic aid to less developed countries is an investment in security for industrial powers or an effort to promote democratic institutions while alleviating poverty. Doyle also considers the future of geopolitics, concluding that even post-millennial humanity will have a divided soul that owes allegiance to the competing claims of many constituencies, of which government is but one. Even so, he argues, the past teaches that enemies can be contained, peace extended, and (if need be) revolutions launched. A world-class yet accessible discourse on the abiding power of political ideas that could furnish reliable guidance to the electorates and leaders of almost any nation on earth.