A Bayesian View on the Dr. Evil Scenario

Journal Article · Tue Jun 21 00:00:00 UTC 2022 · Erkenntnis

DOI: https://doi.org/10.1007/s10670-022-00536-8 · OSTI ID:1873201

Azhar, Feraz; Guth, Alan H.; Namjoo, Mohammad Hossein

Abstract In Defeating Dr. Evil with Self-Locating Belief , Adam Elga proposes and defends a principle of indifference for self-locating beliefs: if an individual is confident that his world contains more than one individual who is in a state subjectively indistinguishable from his own, then he should assign equal credences to the hypotheses that he is any one of these individuals. Through a sequence of thought experiments, Elga in effect claims that he can derive the credence function that should apply in such situations, thus justifying his principle of indifference. Here we argue, using a Bayesian approach, that Elga’s reasoning is circular: in analyzing the third of his thought experiments, he uses an assertion that is justifiable only if one assumes, from the start, the principle of indifference that he is attempting to justify. We agree with Elga that the assumption of equal credences is a very reasonable principle, in the absence of any reason to assign unequal credences, but we do not agree that the equality of credences can be so derived.

• Sponsoring Organization: USDOE
• OSTI ID: 1873201
• Journal Information: Erkenntnis, Journal Name: Erkenntnis Journal Issue: 1 Vol. 89; ISSN 0165-0106
• Publisher: Springer Science + Business MediaCopyright Statement
• Country of Publication: Country unknown/Code not available
• Language: English