Inferential Internalism and Reflective Defeat

Inferential Internalists accept the Principle of Inferential Justification (PIJ), according to which one has justification for believing P on the basis of E only if one has justification for believing that E makes probable P. Richard Fumerton has defended PIJ by appeal to examples, and recently Adam Leite has argued that this principle is supported by considerations regarding the nature of responsible belief. In this paper, I defend a form of externalism against both arguments. This form of externalism recognizes what I call the phenomenon of reflective defeat: if one is justified in not believing that E makes probable P, then this defeats whatever justification one has for believing P upon the basis of E. I argue that this modified version of externalism has the virtue of accommodating the intuitions that motivate internalism, without the cost of the vicious regress that makes internalism so unattractive.