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Paper   IPM / Astronomy / 17592
School of Astronomy
  Title:   A Bayesian View on the Dr. Evil Scenario
1.  F. Azhar
2.  A. H. Guth
3.  M H. Namjoo
  Status:   Published
  Journal: Erkenntnis
  Year:  2022
  Supported by:            ipm IPM
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 Elgaâ??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

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