Knowledge and scepticism

Robert Nozick

pp. 587-603

in: Horacio Arló-Costa, Vincent F. Hendricks, Johan van Benthem (eds), Readings in formal epistemology, Berlin, Springer, 2016

Abstract

You think you are seeing these words, but could you not be hallucinating or dreaming or having your brain stimulated to give you the experience of seeing these marks on paper although no such thing is before you? More extremely, could you not be floating in a tank while super-psychologists stimulate your brain electrochemically to produce exactly the same experiences as you are now having, or even to produce the whole sequence of experiences you have had in your lifetime thus far? If one of these other things was happening, your experience would be exactly the same as it now is. So how can you know none of them is happening? Yet if you do not know these possibilities don't hold, how can you know you are reading this book now? If you do not know you haven't always been floating in the tank at the mercy of the psychologists, how can you know anything-what your name is, who your parents were, where you come from?