Epistemic externalism and the structure of justification

This project is concerned with the attempt to diagnose certain types of deductive inferences as exhibiting failure of transmission of justification. The canonical example of alleged transmission failure is G. E. Moore's infamous 'proof' of the external world, in which Moore reasoned here is a hand, therefore the external world exists. If the transmission failure diagnosis is correct, then this inference is incapable of providing a route to learning of its conclusion on the grounds that it is only if one already has some justification to believe its conclusion that one can acquire justification for its premise. The thesis presents two novel problems for the transmission failure diagnosis. Firstly, this diagnosis is only appealing if it is able to safeguard epistemic closure, but it is unclear whether it is able to do this once we distinguish between propositional and doxastic justification. Secondly, a dilemma is presented for entitlement theory, the traditional framework for understanding how there could be justification for believing the conclusions at issue. The dilemma arises once we consider the question of what the apposite degree of confidence is that is licenced by an entitlement, the upshot of which is that either entitlement theory is unmotivated, or it leads to irrational doxastic attitudes. In light of these problems, an alternative framework for understanding the phenomenon of transmission failure is presented. This framework rejects a common assumption in the literature that we can only accommodate the phenomenon by appealing to internalist notions of justification. The resulting externalist framework is defended against two potentially devastating objections. Finally, implications for how these views regarding the structure of justification bear on issues in the epistemology of testimony are considered, and it is argued that a certain family of views in the literature on testimony are committed to certain problematic views regarding the structure of justification.