Externalists about mental content are supposed to face the following dilemma. Either they must give up the claim that we have privileged access to our own mental states or they must allow that we have privileged access to the world. The dilemma is posed in its most precise form through the McKinsey-Brown argument (McKinsey 1991; Brown 1995). Over the years since it was ?rst published in 1991, our understanding of the precise character of the premisses which constitute the argument has (...) been re?ned. It is based on three claims (where A partially serves to characterise the content of some belief state for which Externalism is true and E is some proposition about the external world). (shrink)