Abstract

As part of Timothy Williamson’s inquiry into how we gain knowledge from thought experiments he submits various ways of representing the argument underlying Gettier cases in modal and counterfactual terms. But all of these ways run afoul of the problem of deviance - that there are cases that might satisfy the descriptions given by a Gettier text but still fail to be counterexamples to the justified true belief model of knowledge). Problematically, this might mean that either it is too hard to know the truth of the premises of the arguments Williamson presents or that the relevant premises might be false. I argue that the Gettier-style arguments can make do with weaker premises (and a slightly weaker conclusion) that suffice to show that “necessarily, if one justifiably believes some true proposition p, then one knows p” is not true. The modified version of the argument is preferable because it is not troubled by the existence of deviant Gettier cases.