Historical counterfactuals, transition periods and the constraints on imagination

The history of how philosophers have dealt with thought experiments in science is the main focus of this special issue. Counterfactual analysis is an interesting subset of thought experiments because it requires the imagination of alternative states of the world (cf also Fearon (1996), Lebow & Stein (1996), Reiss (2009), Tetlock and Belkin (1996) who suggest the same). In historical analysis, the use of imagination is often the focus of criticisms of such counterfactual analysis. In this paper I consider three strategies for constraining imagination; making limited counterfactual changes, limiting counterfactual changes to decisions of important figures, and using evidence to restrict the scope for imagination. Given the focus of this special issue, I will relate this discussion to Lewis’ and Woodward’s analysis of counterfactuals in the philosophy of science. I show that counterfactual analysis in historical cases has some resemblance to Lewis’ and Woodward’s analysis, but that what Lewis calls “transition periods” cannot be left entirely vague, as Lewis suggests, nor can counterfactual changes be seen simply as interventions, as Woodward suggests. I propose that efforts to limit imagination in historical counterfactuals are ultimately problematic, but that imagination can nevertheless play a useful role in counterfactual analysis.