Adhoccery in epistemology

Ernest Sosa has argued that the relevant alternatives theory of knowledge has yet to overcome serious difficulties. The most serious difficulty is that of providing criteria for when a rival alternative to a claim is relevant. Without such criteria, the theory is ad hoc. I argue that most other externalist theories of knowledge, including Sosa’s own, fall victim to this criticism. At the end of the paper I make a suggestion as to why Sosa’s objection might not be as damaging as it at first seems.