The Cartesian conception of the mind, as we have seen, is composed not just of ontological theses concerning the nature of mental phenomena, but also epistemological theses concerning our knowledge of, or access to, such phenomena. These latter we summed up in the slogan: “each person knows his or her mind first and best” – the principle of epistemic internalism. This chapter examines the implications of content externalism for this principle.

Descartes and first-person authority

It is pretty clear that Descartes is committed to at least some version of the principle of epistemic internalism. Consider, for example, the following from the Regulae, §8: “Nothing can be known before the mind, because knowledge of all other things depends on the mind and not the other way around.” This is, of course, a clear statement of the claim that our knowledge of our minds is logically prior to our knowledge of other things including the external world. Knowledge of things outside the mind must be built up from our knowledge of what is going on in our minds, and the former is, therefore, dependent upon the latter. This is reiterated in, for example, the Principles, Part 1, §8, where he writes: