 We have distinguished between Cartesian and Pyrrhonian Skepticism, but we have characterized both views in terms of a generic field of propositions F. In the case of Pyrrhonian Skepticism, F includes every proposition, but we can generate different versions of Cartesian Skepticism by varying F. A prominent version of Cartesian Skepticism is external-world skepticism—i.e., Cartesian Skepticism with respect to any proposition about the “external world” (not about the subject’s own  mind).[4]  In what follows, we concentrate on external world Cartesian Skepticism and Pyrrhonian Skepticism.