Case Studies and Theory Development in the Social Sciences - Alexander L. George [111]
Perhaps enough has been said to emphasize and illustrate that there are a number of distinctively different types of process-tracing just as there are different types of causal processes. The challenge in using process-tracing is to choose a variant of it that fits the nature of the causal process embedded in the phenomenon being investigated.
Uses of Process-Tracing
Case studies are useful, as Harry Eckstein and Arend Lijphart noted many years ago, at all stages in the formation, development, and testing of theories.428 Moreover, deductive theories (including rational choice theories) and empirical theories derived inductively can be employed using one or another type of process-tracing. Those who cite Achen and Snidal’s critique of existing case studies of deterrence often overlook the authors’ emphasis on the critical importance of case studies for theory development and testing:
Although many of our comments have criticized how case studies are used in practice, we emphatically believe they are essential to the development and testing of social science theory… . In international relations, only case studies provide the intensive empirical analysis that can find previously unnoticed causal factors and historical patterns… . The [case study] analyst is able to identify plausible causal variables, a task essential to theory construction and testing… . Indeed, analytic theory cannot do without case studies. Because they are simultaneously sensitive to data and theory, case studies are more useful for these purposes than any other methodological tool.429
The study of macro- as well as microlevel phenomena benefits from uses of process-tracing. The utility of process-tracing is not restricted to the study of the intentional behavior of actors and organizations; it is also applicable, as in Theda Skocpol’s study of States and Revolution, to investigations of any hypothesized causal process. An interest in studying process is to be seen also in the use of simulations, as in the recent work of Bruce Bueno de Mesquita and Frans Stokman.430 And, as is increasingly clear, process-tracing is particularly important for generating and assessing evidence on causal mechanisms.431
More generally, process-tracing offers an alternative way for making causal inferences when it is not possible to do so through the method of controlled comparison. In fact, process-tracing can serve to make up for the limitations of a particular controlled comparison. When it is not possible to find cases similar in every respect but one—the basic requirement of controlled comparisons—one or more of the several independent variables identified may have causal impact. Process-tracing can help to assess whether each of the potential causal variables in the imperfectly matched cases can, or cannot, be ruled out as having causal significance. If all but one of the independent variables that differ between the two cases can be ruled out via a process-tracing procedure that finds no evidence that they were operating in the two cases, a stronger (though still not definitive) basis exists for attributing causal significance to the remaining variable. The case for it is strengthened, of course, if process-tracing uncovers evidence of the role of that variable in the process leading to the outcome.432
In the same way, process-tracing can ameliorate the limitations of John Stuart Mill’s methods of agreement and difference. For example, process-tracing offers a way of assessing hypotheses regarding causal relations suggested by preliminary use of Mill’s methods, as in Theda Skocpol’s study.433 More generally, process-tracing can identify single or different paths to an outcome, point out variables that were otherwise left out in the initial comparison of cases, check for spuriousness,