The political spectrum has often been viewed as a linear continuum on which the extremes of the right and left occupy the most antithetical positions. The alternative hypothesis is that there are some dimensions on which the extremes resemble each other. This essay examines the theories of international politics and foreign policy espoused by scholars of the radical right and left. Two dozen points of convergence are grouped under five headings: Understanding history and politics, the causes of war, the nature of the enemy, the conditions of peace, and ends and means in politics. Because the essay is focused on studies of international politics since the outbreak of World War II, considerable attention is devoted to the parallels between rightwing theories of the USSR and Soviet foreign policy, and left wing explanations of the United States and American foreign policy. The conclusion suggests that both theories are fundamentally flawed in two respects: (1) As employed by their proponents, the theories appear incapable of being falsified; and (2) studies employing them are marred by serious methodological flaws that violate the canons of systematic inquiry.

Four major new compilations of macropolitical data are compared and evaluated. Each summarizes a large-scale research effort to code or to collect data suitable for theoretically relevant, cross-national comparisons. As a group the new handbooks incorporate many improvements and innovations on earlier handbooks, which concentrated mainly on cross-sectional, aggregate data or simplistically coded judgments about nation-states. About a third of their measures consist of “made” data, derived by coding journalistic and historical sources. All provide some measures for cross-time comparisons; one is devoted exclusively to time-series data. Many of their measures denote properties of internal and international conflict and of international transactions. All but one are painfully self-conscious about problems of reliability and comparability of data. One criticism is the reliance of several of the handbooks on “counts” of conflict events rather than assessment of more theoretically relevant properties of conflict. A second is the paucity of indicators of inequality and, more generally, of measures which give a “view from the bottom” of political systems.