The role of variation in thought experiments

The main concern of this paper is to show that understanding mental variation may prove to be relevant to inquiry into thought experiments. First, I examine why Ernst Mach considered the ability to vary the contents of one's thoughts the principal requirement for thought experimentation. Second, I illustrate the wide applicability of mental variation in thought experiments. Third, I suggest, following Kathleen Wilkes, that variation is frequently employed in "realistic" thought experiments.