Cartesian skepticism has been a hot topic lately at TSZ. I’ve been defending a version of it that I’ve summarized as follows:
Any knowledge claim based on the veridicality of our senses is illegitimate, because we can’t know that our senses are veridical.
This means that even things that seem obvious — that there is a computer monitor in front of me as I write this, for instance — aren’t certain. Besides not being certain, we can’t even claim to know them, and that remains true even when we use a standard of knowledge that allows for some uncertainty. (There’s more — a lot more — on this in earlier threads.)
In explaining to Kantian Naturalist why I am a Cartesian skeptic, I introduced the analogy of the Sentinel Islander:
