Intuitively, it seems that the victims of evil demons (or of other similarly radical deceivers) may be perfectly rational or justified in the way in which they form, maintain, and revise their beliefs and other attitudes. Indeed, whether or not an agent is being deceived in this way seems irrelevant to the question of whether or not the agent’s thinking is rational. This seems to support what epistemologists would call an “internalist” conception of rationality – according to which the truth about how it is rational for an agent to think supervenes on “internal” facts about what is going on in the agent’s mind.

However, this internalist conception of rationality raises a number of questions: (a) What is its relation to the view that is sometimes called “internalism” in the philosophy of mind – the view that all real mental states supervene on “narrow” states of the agent? (b) How exactly are we to draw the line between “internal” facts about the agent’s mind and “external” facts about the agent’s relations to her environment? (c) Even if an internalist conception of rationality is true, why is it true? This talk will offer an answer to these three questions – thereby (it may be hoped) bolstering this internalist conception against some of the objections that have been raised against it.