But where is a hallucinator's perceptual justification?
pp. 155-161
in: Richard S. BROWN (ed), Consciousness inside and out, Berlin, Springer, 2014Abstract
Sam sees a tomato on the table before her, and sees its redness. Call this situation "the good case". In virtue of seeing the tomato and its redness, Sam is justified in believing that there is a red tomato before her—at least, that's what we ordinarily think. However, it is possible for Sam to have a subjectively indistinguishable experience in which she sees a tomato, but doesn't see its color (e.g., an illusory experience in which the subject sees a white tomato bathed in red light), or in which she doesn't see anything in her environment at all (e.g., a total hallucination "as of" a red tomato). Call these situations "the bad cases". In light of such possibilities, it's hard to resist the conclusion that Sam's good case experience bestows no more justification on the claim that there is a red tomato before her than it does on (e.g.) the claim that there is a white tomato bathed in red light before her. So how can Sam's belief that there is a red tomato before her be perceptually justified? (As is well known, a structurally similar problem can be raised about whether Sam's perceptually-based belief amounts to knowledge.)