Most content externalists concede that even if externalism is compatible with the thesis that one has authoritative self-knowledge of thought contents, it is incompatible with the stronger claim that one is always able to tell by introspection whether two of one’s thought tokens have the same, or different, content. If one lacks such authoritative discriminative self-knowledge of thought contents, it would seem that brute logical error – non-culpable logical error – is possible. Some philosophers, such as Paul Boghossian, have argued (...) that this would present a big problem for externalism, forcing the externalist to overhaul our norms of rationality. I consider several externalist strategies to block this possibly unhappy epistemological consequence, but I argue that they all fail. (shrink)