To do one or a few case study requires having a rationale for choosing among potentially hundreds of cases. In contrast to the existing literature, this paper argues that there is one dominant goal for a case study: exploring causal mechanisms. The methodological question then becomes what is the logic of case selection when this is the goal. Within a QCA framework this becomes case selection when one has a causal mechanism which is sufficient for the outcome, i.e., the causal mechanism produces the outcome. Case selection strategies in this setup differ quite significantly from those motivated by cross-case and statistical views of multimethod or qualitative analysis. In part this difference lies in that qualitative scholars believe that within-case causal inference is possible, while statistical researchers require cross-case evidence; this has dramatic consequences on case selection strategies.
