 McKinsey (1991, 2002, 2003 and 2007) has offered a reductio argument for the incompatibility of first-person privileged access to mental content and externalism about mental content. The privileged access thesis roughly says that it is necessarily true that if a subject s is thinking that x, then s can in principle know a priori (or in a non-empirical way) that she herself is thinking that x. Externalism about mental content roughly says that predicates of the form ‘is thinking that x’—e.g., ‘is thinking that water is wet’—express properties that are wide, in the sense that possession of these properties by s logically or conceptually implies the existence of relevant contingent objects external to s’s mind—e.g., water. McKinsey argues that s may reason along these lines: