The Logic of Inference of Thought Experiments in Political Theory

This Paper explains the logic of inference of thought experiments in political theory. Extending the work of Frances Kamm, I show that many thought experiments are similar to natural science controlled experiments, and to ‘most similar systems’ comparisons in political science: we hold all variables constant except one, then see the effect. The scientific parallel leads me to make recommendations such as changing variables one by one, looking for interaction effects, distinguishing between internal and external validity, and so on. I thus build on the work of scholars such as Kimberley Brownlee and Zofia Stemplowska to produce a fuller set of methodological guidelines for thought experiments than has previously been achieved. This has three benefits. (1) It helps us assess the strengths and weaknesses of existing thought experiments, and improve some of them. We can even get useful insights from flawed thought experiments like the ticking time-bomb scenario. (2) Some criticisms of thought experiments turn out to be objections not to thought experiments in general, but merely to particular ways in which they have been applied. (3) I highlight similarities between some aspects of political theory and political science. To paraphrase one of the greatest contemporary exponents of thought experiments, Derek Parfit: political theorists and political scientists sometimes use the same tools even when they are climbing different mountains.