A Remark on Luminosity

Timothy Williamson defines a property of luminosity in the following manner: a condition (or a mental state of a given subject) is luminous if and only if “whenever it obtains (and one is in a position to wonder whether it does), one is in a position to know that it obtains”. Williamson claims that “for virtually no mental state S is the condition that one is in S luminous”. But Wai-hung Wong observes that Williamson’s argumentation for non-luminosity of mental states is dangerously similar in its form to the reasoning underlying the sorites paradox. The observation lead him to the question: is it possible to prove the non-luminosity of some mental states without appeal to a reasoning analogous to the one underlying the sorites paradox? In the paper I present an argument in favour of the claim that Wong’s problem expressed in the question can be resolved. I present a method of determining whether a given state is luminous. However, the proposed test is fragmentary in the sense that it allows us to identify non-luminous states only within the set of propositional attitudes that fulfil certain conditions specified in the paper.