Incompatibility Arguments and Semantic Self Knowledge

There has been much discussion recently of what has been labeled the “Brown-Boghossian-McKinsey”, “Brown-McKinsey” or sometimes just “McKinsey” arguments for the incompatibility of externalism and self-knowledge. However, while the three author’s arguments have been treated as interchangeable, they are not identical. In particular, Brown’s and Boghossian’s arguments have a fairly serious flaw that cannot so easily be attributed to McKinsey. In what follows, I’ll (1) present a version of the ‘received’ “Brown-Boghossian-McKinsey” argument, (2) outline what I take to be the most serious objection to it, (3) explain why this sort of objection does not seem, or do not seem immediately, to tell against McKinsey’s argument, and (4) suggest a number of alternative responses that might apply to McKinsey as well. The “Brown-Boghossian-McKinsey” (BB) argument against the compatibly of Externalism and Self-Knowledge is correctly attributed to Jessica Brown, and Paul Boghossian, and it runs something like this: