In the first part of the paper, I will argue that it makes sense to distinguish three different approaches to case study research (co-variational analysis, causal-process tracing, congruence analysis). The three approaches have distinct goals, different ontological presuppositions and epistemological affinities; they apply quite different case selection strategies and techniques of drawing causal inferences, and finally, they draw different kinds of conclusions beyond the investigated cases, in other words, they have diverse directions of generalization.
The second part of the paper focuses on causal-process tracing (CPT), which can be conceptualized as a distinct case study approach with specific goals (Y-centered research questions) and ontological starting points (contingency and configurational causation). It can also be conceived as a specific technique of drawing causal inferences with an affinity to scientific realist epistemologies. It relies heavily on the fact that causation plays out in time and space and combines three kinds of observations (comprehensive story lines, smoking guns and confessions) with formal logic, counterfactual reasoning and theory-based causal mechanisms in order to draw causal inferences. Crucially important is the recognition that it generalises its findings not towards populations of similar cases but towards sets of “possible” causal configurations or causal mechanisms.
Finally, it will be argued that such an inductive conceptualization of causal-process tracing has the largest potential to complement other, more deductive, approaches in small-N as well as in medium- or large-N research. This will be illustrated with a concrete example of case study research.
