Three attempts to refute skepticism and why they fail

One of the advantages of classical foundationalism was that it was thought to provide a refutation of skeptical worries, which raise the specter that our beliefs might be extensively mistaken. The most extreme versions of these worries are expressed in familiar thought experiments such as the brain-in-a-vat hypothesis, which imagines a world in which, unbeknownst to you, your brain is in a vat hooked up to equipment programmed to provide it with precisely the same visual, auditory, tactile, and other sensory inputs that you have in this world. As a result, your opinions about your immediate environment are the same as they are in this world. You have the same beliefs about your recent activities, your current physical appearance, your present job, and so on, but in fact you are a brain in a vat tucked away in a corner of a laboratory. Thus, in the brain-in-a-vat world, your beliefs about these everyday matters are mistaken, and mistaken not just in detail, but deeply mistaken.