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Justifying conditionalization: Conditionalization maximizes expected epistemic utility

Greaves, Hilary and Wallace, David (2005) Justifying conditionalization: Conditionalization maximizes expected epistemic utility. [Preprint]

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According to Bayesian epistemology, the epistemically rational agent updates her beliefs by conditionalization: that is, her posterior subjective probability after taking account of evidence X, p_{new}, is to be set equal to her prior conditional probability p_{old}(.|X). Bayesians can be challenged to provide a justification for their claim that conditionalization is recommended by _rationality_ --- whence the normative force of the injunction to conditionalize? There are several existing justifications for conditionalization, but none directly addresses the idea that conditionalization will be epistemically rational if and only if it can reasonably be expected to lead to _epistemically good outcomes_. We apply the approach of cognitive decision theory to provide a justification for conditionalization using precisely that idea. We assign epistemic utility functions to epistemically rational agents; an agent's epistemic utility is to depend both upon the actual state of the world and on the agent's credence distribution over possible states. We prove that, under independently motivated conditions, conditionalization is the unique updating rule that maximizes expected epistemic utility.

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Item Type: Preprint
Greaves, Hilary
Wallace, David
Keywords: Epistemic rationality; conditionalization; bayesianism; cognitive decision theory
Subjects: General Issues > Decision Theory
General Issues > Confirmation/Induction
Depositing User: Hilary Greaves
Date Deposited: 01 Mar 2005
Last Modified: 07 Oct 2010 15:13
Item ID: 2212

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