Epistemic closure in folk epistemology

This chapter reports the results of four empirical studies that investigate the extent to which an epistemic closure principle for knowledge is reflected in folk epistemology. Previous work by Turri (2015a) suggested our shared epistemic practices may only include a closure principle that applies to perceptual beliefs but not to inferential beliefs. The chapter argues that the results of these studies provide reason for thinking individuals are making a performance error when their knowledge attributions and denials conflict with the closure principle. When the chapter authors used research materials that overcome proposed difficulties with Turri’s original materials, they found that participants did not reject closure. Furthermore, when they presented Turri’s original materials to non-philosophers with expertise in deductive reasoning, they endorsed closure for both perceptual and inferential beliefs. These results suggest that an unrestricted closure principle provides a better model of folk patterns of knowledge attribution than a source-relative one.