No validation of our rationality - of our very sanity - can be accomplished using our rationality itself. How can a person operating within a system of beliefs, including beliefs about beliefs, get outside that system to determine whether it is rational? If your entire system becomes infected with madness, including the very rules by which you reason, then how can you ever reason your way out of your madness?
Rebecca Goldstein, Incompleteness: The Proof and Paradox of Kurt Gödel
beliefs, rationality, reality, sanity