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A Bayesian View on the Dr. Evil Scenario

Azhar, Feraz and Guth, Alan H. and Namjoo, Mohammad Hossein (2021) A Bayesian View on the Dr. Evil Scenario. [Preprint]

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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.


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Item Type: Preprint
Creators:
CreatorsEmailORCID
Azhar, Ferazfazhar@nd.edu
Guth, Alan H.guth@ctp.mit.edu
Namjoo, Mohammad Hosseinmh.namjoo@ipm.ir0000-0002-3093-4766
Keywords: Principle of Indifference, self-locating belief, Bayesian reasoning
Subjects: Specific Sciences > Physics > Cosmology
General Issues > Decision Theory
Specific Sciences > Probability/Statistics
General Issues > Thought Experiments
Depositing User: Dr. Feraz Azhar
Date Deposited: 26 Mar 2021 13:13
Last Modified: 26 Mar 2021 13:13
Item ID: 18845
Subjects: Specific Sciences > Physics > Cosmology
General Issues > Decision Theory
Specific Sciences > Probability/Statistics
General Issues > Thought Experiments
Date: 22 March 2021
URI: http://philsci-archive.pitt.edu/id/eprint/18845

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