This paper examines Laurence BonJour's defense of internalism inThe Structure of Empirical Knowledge with an eye toward better understanding the issues which separate internalists from externalists. It is argued that BonJour's Doxastic Presumption cannot play the role which is required of it to make his internalism work. It is further argued that BonJour's internalism, and, indeed, all other internalisms, are motivated by a Cartesian view of an agent's access to her own mental states. This Caretsian view is argued to be untenable, and, accordingly, so is internalism.