Williamson’s anti-luminosity argument has further consequences. If sound, not only would it show that it can be irrational for one to believe a given proposition without one’s being in a position to know that it is, but it would also establish that one can be in pain without one’s being in a position to know that one is; that one can seem to see a certain color without one’s being in a position to know that one does; that two words can mean the same thing in one’s idiolect without one’s being in a position to know that they do; and that a given proposition can be part of one’s evidence without one’s being in a position to know that it is. In other words, the argument would show that one’s current mental life, the meanings of one’s words, the extent of one’s evidence, and the dictates of rationality are all non-luminous — that each can, at least in principle, be epistemically inaccessible to a given subject. If Williamson is right, then we are (as he puts it) “cognitively homeless”: there is no substantive domain of mental or semantic or normative facts to which we have guaranteed access, no subportion of our mental or semantic or normative lives within which everything lies open to view.0
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