Subjective values should be sharp
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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.
KeywordsSubjective value Subjective probabilities Preferences Parity Vague value Incomparability Sequential decisions Money pumps
I would especially like to thank Peter Vallentyne, Paul Weirich, and the anonymous reviewers at Synthese for their comments on several revisions of this article. I am also grateful for helpful feedback (regarding this article or its predecessors) from Robert Johnson, Ruth Chang, Martin Peterson, Joshua Gert, Henrik Andersson, and the participants of the Formal Ethics 2019 conference.
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