One of the ways in which the social sciences have changed over the last 20 years is an increased focus on trying to understand how people think about matters of interest to philosophers. This is best illustrated by the fluorescence of work in moral psychology. Moral psychologists have explored both what people think about morality, and the psychological foundations for those beliefs. In this talk, I will pursue a new strand of inquiry focused on ordinary presumptions about explanation.

According to a simple version of the Principle of Sufficient Reason (PSR), for every fact, there must be an explanation of that fact. The PSR has been influential in philosophy for centuries. Do ordinary people presuppose something like the PSR in their explanatory judgments? We find that they do, based on studies with adults and children in the US as well as adults in India with little formal education. These empirical results promise to reflect back on philosophy. The intuitiveness of the PSR might help explain why, even in the absence of adequate evidence, philosophers are attracted to views like determinism and reductionism.