The Probability Problem in Everettian Quantum Mechanics Persists

Bibliographic Data

ID8397267
AuthorsFoad Dizadji-Bahmani (London School of Economics and Political Science, corresponding author)
Year2015
Volume66
Issue2
Pages257-283
Publication date2015-06-01
Peer ReviewedYes
Open AccessNo
TypeARTICLE
VenueThe British Journal for the Philosophy of Science (JOURNAL)
Journal identifiersISSN: 0007-0882 • E-ISSN: 1464-3537
PublisherOxford University Press (PUBLISHER • GB)
DOI10.1093/bjps/axt035
OpenAlexW2319081112
LanguageEN
Citations received12
References cited10

Everettian quantum mechanics (EQM) results in ‘multiple, emergent, branching quasi-classical realities’ (Wallace [2012]). The possible outcomes of measurement as per ‘orthodox’ quantum mechanics are, in EQM, all instantiated. Given this metaphysics, Everettians face the ‘probability problem’—how to make sense of probabilities and recover the Born rule. To solve the probability problem, Wallace, following Deutsch ([1999]), has derived a quantum representation theorem. I argue that Wallace’s solution to the probability problem is unsuccessful, as follows. First, I examine one of the axioms of rationality used to derive the theorem, ‘branching indifference’ (BI). I argue that Wallace is not successful in showing that BI is rational. While I think it is correct to put the burden of proof on Wallace to motivate BI as an axiom of rationality, it does not follow from his failing to do so that BI is not rational. Thus, second, I show that there is an alternative strategy for setting one’s credences in the face of branching which is rational and which violates BI. This is ‘branch counting’ (BC). Wallace is aware of BC and has proffered various arguments against it. However, third, I argue that Wallace’s arguments against BC are unpersuasive. I conclude that the probability problem in EQM persists. 1 Introduction 2 Branching Indifference 2.1 The positive argument for branching indifference 2.2 The negative argument for branching indifference 2.3 Branching indifference section summary 3 Branch Counting 3.1 Branch counting is rational under the subjective-uncertainty viewpoint 3.2 Branch counting is rational under the objective-determinism viewpoint 3.3 Branch counting section summary 4 Number of Branches 4.1 Veracity of the framework 4.2 No such thing as the number of branches 4.2.1 The number of branches is indeterminate 4.2.2 The number of branches is indeterminable 4.3 Rationality and weight 5 Conclusion

Argument (complex analysis) · Axiom · Branching (polymer chemistry) · Discrete mathematics · Epistemology · Face (sociological concept) · Mathematical economics · Metaphysics · Rational number · Rationality · Mathematics · Philosophy · Philosophy and History of Science · Quantum Mechanics and Applications · Statistical Mechanics and Entropy

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