ABSTRACT
Exotic thought experiments have often played a critical role in evaluating philosophical issues about the nature and epistemological significance of perception and memory. In raising initial concerns about what we know, Descartes (1999 [1641]) famously (if not originally) invokes the possibility that all of the experiences we take to be veridical (experiences we take to be of waking life) might instead be experiences of a vivid dream. He went on to suggest that it is at least conceivable that there exists a very powerful but evil demon exercising his power to induce in you hallucinatory experience qualitatively indistinguishable from the experiences you take to be veridical. On either possibility, your beliefs about your physical surroundings based on those experiences might involve massive error. Many contemporary epistemologists preoccupied with cognitive science often prefer invoking the possibility that your brain has been stolen and now lies in a vat, subject to the experiments of a mad neuroscientist. That scientist is stimulating your brain so as to produce the neuronal activity that either is (according to some philosophers), or is the immediate cause of (according to others), sensory experience in all of its glorious detail.
