Case Studies and Theory Development in the Social Sciences - Alexander L. George [107]
Another leading contributor to comparative politics, Peter Hall, also stresses the importance of “theory-oriented process-tracing.” Hall observes that “we might usefully turn to the techniques that George (1979) initially termed ‘process-tracing’ [which] points us in the right methodological direction.” He concludes, “In short, process-tracing is a methodology well-suited to testing theories in a world marked by multiple interaction effects, where it is difficult to explain outcomes in terms of two or three independent variables—precisely the world that more and more social scientists believe we confront.”411
Process-tracing finds a place also in the constructivist approach. Alexander Wendt recognizes that the core of descriptions of causal mechanisms is “process-tracing, which in social science ultimately requires case studies and historical scholarship.”412
This chapter considerably develops our analyses of process-tracing, dating back to 1979. The process-tracing method attempts to identify the intervening causal process—the causal chain and causal mechanism—between an independent variable (or variables) and the outcome of the dependent variable. Suppose that a colleague shows you fifty numbered dominoes standing upright in a straight line with their dots facing the same way on the table in a room, but puts a blind in front of the dominoes so that only number one and number fifty are visible. She then sends you out of the room and when she calls you back in you observe that domino number one and domino number fifty are now lying flat with their tops pointing in the same direction; that is, they co-vary. Does this mean that either domino caused the other to fall? Not necessarily. Your colleague could have pushed over only dominoes number one and fifty, or bumped the table in a way that only these two dominoes fell, or that all the dominoes fell at once. You must remove the blind and look at the intervening dominoes, which give evidence on potential processes. Are they, too, lying flat? Do their positions suggest they fell in sequence rather than being bumped or shaken? Did any reliable observers hear the sound of dominoes slapping one another in sequence? From the positions of all the dominoes, can we eliminate rival causal mechanisms, such as earthquakes, wind, or human intervention? Do the positions of the fallen dominoes indicate whether the direction of the sequence was from number one to number fifty or the reverse?
These are the kinds of questions researchers ask as they use process-tracing to investigate social phenomena. Tracing the processes that may have led to an outcome helps narrow the list of potential causes. Yet even with close observation, it may be difficult to eliminate all potential rival explanations but one, especially when human agents are involved—for they may be doing their best to conceal causal processes. But process-tracing forces the investigator to take equifinality into account, that is, to consider the alternative paths through which the outcome could have occurred, and it offers the possibility of mapping out one or more potential causal paths that are consistent with the outcome and the process-tracing evidence in a single case. With more cases, the investigator can begin to chart the repertoire of causal paths that lead to a given outcome and the conditions under which they occur—that is, to develop a typological theory.
Process-tracing is an indispensable tool for theory testing and theory development not only because it generates numerous observations within a case, but because these observations must be linked in particular ways to constitute an explanation of the case. It is the very lack of independence among