A new argument for the incompatibility of content externalism with justification internalism

Several lines of reasoning have been proposed to show the incompatibility of content externalism with justification internalism. In this paper I examine two such lines of reasoning, which both rely on the general idea that since content externalism is incompatible with certain aspects of the alleged privileged character of self-knowledge, it would tend to undermine justification internalism as well. I shall argue that both lines of reasoning, as they stand, lack plausibility, though the core idea of the second line can be reconstructed into a new argument which shows considerable promise. In particular, relying upon the reliability constraint on knowledge, I shall argue that the so-called ‘two-concept’ version of content externalism is incompatible with ‘the transparency of sameness of content’, and thereby would also undermine justification internalism.