Externalism, transparency, and diagonal propositions

Boghossian (Philos Perspect 8:33–50, 1994) argued (a) that externalism is incompatible with a transparency thesis according to which we can know priori whether any two of our occurrent thoughts have the same or distinct content, and (b) this integral commonsense conception rationality, requires apriority logical abilities. Stalnaker (Our knowledge internal world, Oxford University Press, Oxford, 2008) offered detailed compatibilist response Boghossian. Stud 155:457–465, 2011) criticized response, 155:467–479, replied. But outcome important discussion remained unclear, partly because it was unclear how understand amended at gesturing. My aim in paper settle matter. I wish (i) clarify terms debate, also by highlighting relevant commitments Stalnaker’s two-dimensionalist account, (ii) show his appeals diagonal propositions, unsuccessful.