This article surveys the extensive new literature that has brought about a renaissance of qualitative methods in political science over the past decade. It reviews this literature's focus on causal mechanisms and its emphasis on process tracing, a key form of within-case analysis, and it discusses the ways in which case-selection criteria in qualitative research differ from those in statistical research. Next, the article assesses how process tracing and typological theorizing help address forms of complexity, such as path dependence and interaction effects. The article then addresses the method of fuzzy-set analysis. The article concludes with a call for greater attention to means of combining alternative methodological approaches in research projects.

This article discusses the application of qualitative methods in analyzing causal complexity. In particular, the essay reviews how process tracing and systematic case comparisons can address path-dependent explanations. The article unpacks the concept of path dependence and its component elements of causal possibility, contingency, closure of alternatives, and constraints to the current path. The article then reviews four strengths that case studies bring to the study of path dependence: offering a detailed and holistic analysis of sequences in historical cases, being suitable for the study of rare events, facilitating the search for omitted variables that might lie behind contingent events, and allowing for the study of interaction effects within one or a few cases.

Why do states contribute to alliances? Is relative size the principal factor influencing the size of contributions, as many studies suggest, or are perceptions of threat, dependencies on other alliance members, and domestic institutions and policies equally important? These questions hold unusual interest in the wake of the cold war. The end of bipolarity promises more ad hoc coalitions, which will widen opportunities for research on alliance burden-sharing beyond the North Atlantic Treaty Organization (NATO). At the same time, because the political fault lines of the cold war have disappeared, there are few accepted political criteria for sharing those security burdens that are perceived collectively.

Theorizing under the rubric of paradigmatic ‘isms’ has made important conceptual contributions to International Relations, but the organization of the subfield around these isms is based on flawed readings of the philosophy of science and has run its course. A promising alternative is to build on the philosophical foundation of scientific realism and orient International Relations theorizing around the idea of explanation via reference to hypothesized causal mechanisms. Yet in order to transform the practice of International Relations theorizing and research, calls for ‘analytic eclecticism’ must not only demonstrate that scientific realism is a defensible epistemology amenable to diverse methods; they must provide a structured and memorable framework for diverse and cumulative theorizing and research, field-wide discourse, and compelling pedagogy. I Introduce a ‘taxonomy of theories about causal mechanisms’ as a structured pluralist framework for encompassing the theories about mechanisms of power, institutions, and legitimacy that have been providing the explanatory content of the isms all along. This framework encourages middle-range or typological theorizing about combinations of causal mechanisms and their operation in recurrent contexts, and it offers a means of reinvigorating the dialogue between International Relations, the other subfields of political science, and the rest of the social sciences.

This article reviews the key role that case study methods have played in the study of international relations (IR) in the United States. Case studies in the IR subfield are not the unconnected, atheoretical, and idiographic studies that their critics decry. IR case studies follow an increasingly standardized and rigorous set of prescriptions and have, together with statistical and formal work, contributed to cumulatively improving understandings of world politics. The article discusses and reviews examples of case selection criteria (including least likely, least and most similar, and deviant cases); conceptual innovation; typo-logical theories, explanatory typologies, qualitative comparative analysis, and fuzzy-set analysis; process tracing; and the integration of multiple methods.