Between complexity and parsimony: limited diversity, counterfactual cases, and comparative analysis

Counterfactual analysis has a long and distinguished history in comparative research. To some, counterfactual analysis is central to comparative inquiry because such research typically embraces only a handful of empirical cases (Fearon 1991). If there are only a few instances (e.g., of revolution), then researchers, of necessity, must compare empirical cases to hypothetical cases. The affinity between counterfactual analysis and comparative research, however, derives not from its focus on small Ns, but from its configurational nature. Case-oriented explanations of outcomes are often combinatorial in nature, stressing specific configurations of causal conditions. Rather than focus on the net effects of causal conditions, case-oriented explanations emphasize their combined effects. To support an argument emphasizing combinations of causal conditions, it is necessary for researchers to compare cases that are closely matched with each other. The ideal comparison is between pairs of cases that differ on only one causal condition (Mill 1843). Such comparisons help researchers establish whether or not a specific causal condition is an integral part of the combination of conditions that generates the outcome in question. It is very difficult to match empirical cases in this manner, however, due to th