Subjective values should be sharp

Elga (Philos Impr 10(5): 1-10, 2010) has argued that, even when no particular subjective probability is required by one's evidence, perfectly rational people will have sharp subjective probabilities. Otherwise, they would be rationally permitted to knowingly turn down some sure gains. I argue that it is likewise true that, even when we do not possess enough practical reasons for a sharp evaluation (because of optionality or ignorance), perfectly rational people will have sharp subjective values. Those who would be most inclined to reject this argument are those who claim that we are rationally required by either our beliefs that objective values are unsharp (such as strong incomparability, vague value, or parity) or by our own 'real' values to have unsharp subjective values. Regarding the former claim, I show that we need not believe that all objective values are sharp to rationally have unsharp subjective values. Regarding the latter claim, I conclude that sharpened subjective values must be 'real' (i.e., practically authoritative) because otherwise perfect rationality would be impossible in principle.