Abstract
The aim of this paper is to show how thought experiments help us learn about laws. After providing examples of this kind of nomic illumination in the first section, I canvass explanations of our modal knowledge and opt for an evolutionary account. The basic application is that the laws of nature have led us to develop rough and ready intuitions of physical possibility which are then exploited by thought experimenters to reveal some of the very laws responsible for those intuitions. The good news is that natural selection ensures a degree of reliability for the intuitions. The bad news is that the evolutionary account seems to limit the range of reliable thought experiment to highly practical and concrete contexts. In the fifth section, I provide reasons for thinking that we are not as slavishly limited as a pessimistic construal of natural selection suggests. Nevertheless, I promote the idea that biology is a promising source of predictions and diagnoses of thought experiment failures.