Case Studies and Theory Development in the Social Sciences - Alexander L. George [130]
Reducing the Property Space
The first criterion for reducing the property space is to remove types that are not socially possible.493 A good theory may be able—in time, if not immediately—to specify hypothetical cases or combinations of variables that should not exist or should at least be highly unlikely.494 In other words, a particular outcome may be impossible when the independent variables overdetermine a different outcome. For example, we do not expect deterrence to fail when the deterrer has overwhelming and usable instruments of force, is far more committed to success than the opponent, communicates its intentions clearly, and faces a rational, unified, and attentive opponent. If we do find a failure under such circumstances, it may be treated as a deviant case, which may suggest new variables that need to be added to our typological theory.495
Delineating types within the property space and developing a preliminary typological theory enables researchers to check whether they have been premature in deciding whether some types should not, according to the theory, exist in the social world. In other words, rather than merely assuming that the types which the theory predicts to be empty are in fact empty, the researcher should carefully consider whether there might be historical cases that fit these types, or whether such cases could occur in the future.496 One constraint on typological theorizing, like that on John Stuart Mill’s methods as discussed in Chapter 8, is that the social world has not necessarily produced cases of all the types of a phenomenon that are socially possible, and we cannot be certain whether a type of case cannot occur or merely has not yet occurred. The disciplined use of counterfactual inquiries is one way to fill in empty types for the purposes of comparison to actual cases. Fortunately, not all research designs require a fully inhabited property space. Single cases, if they are most-likely, least-likely, or especially crucial cases, can be quite revealing about the strength of a theory. Comparisons of a few cases, if they are most similar or least similar, can also be revealing.
Still, although single-case research designs and no-variance designs involving only the study of cases that are positive on the outcome of interest are valid, researchers sometimes make the basic mistake of overgeneralizing from cases where the hypothesized cause and the hypothesized effect are both present. While there are valid research designs that use only one case study, or that focus on all the possible paths to a given effect or all the possible effects from a given cause, ideally the researcher should examine or at least invite others to propose and study cases where the hypothesized cause or effect are absent. More generally, when working with any given property space, the investigator’s causal inferences will be strongest if she or he attempts to study (or at least contemplates) cases of various types.
Consider, for example, a simple version of the democratic peace hypothesis, in which states are either democracies or nondemocracies, and in which dyads have either engaged in war or maintained a peace. With these three dichotomous variables (democracy or nondemocracy for the first state, the same for the second, and either war or peace