Abstract

Epistemologists have had some difficulties in accounting for purported Gettier-type cases that elicit divergent intuitions on whether or not the protagonist knows a certain target-proposition she believes. These are the so-called ‘penumbral cases’, a paradigmatic example of which is the Newspaper Case, put forward by Gilbert Harman, back in 1968. Penumbral cases are called this way because they seem to highlight an interesting and not widely recognized vagueness of the concept of knowledge. Peter Klein’s defeasibility theory has found a way to deal with those troublesome cases, and it was advertised by him that, among many other theories of knowledge then prominent in the literature, such an account had the best promise of accommodating those cases. I agree with Klein in that respect. I do believe that the defeasibility theory has the appropriate resources to deal with cases that exhibit the inherent vagueness of the concept of knowledge. What is more, defeasibilists are able to handle another interesting type of case that many theories have trouble with, and they might do so using the same apparatus they use to handle the old penumbral cases, like Harman’s. Defeasibilists are able to handle the alleged cases of unsafe knowledge, namely, intuitive cases of knowledge that are classified as cases of ignorance by the popular safety theory. Besides showing this is the case, my aim in this paper is to show that such an advantage of defeasibilism reveals the superiority of this theory over its rivals by plausible considerations regarding theory choice.