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UBC Theses and Dissertations

Information theory and partial belief reasoning Lukits, Stefan Hermann


The dissertation investigates the nature of partial beliefs and norms governing their use. One widely accepted (though not uncontested) norm for partial belief change is Bayesian conditionalization. Information theory provides a far-reaching generalization of Bayesian conditionalization and gives it a foundation in an intuition that pays attention principally to information contained in probability distributions and information gained with new evidence. This generalization has fallen out of favour with contemporary epistemologists. They prefer an eclectic approach which sometimes conflicts with norms based on information theory, particularly the entropy principles of information theory. The principle of maximum entropy mandates a rational agent to hold minimally informative partial beliefs given certain background constraints; the principle of minimum cross-entropy mandates a rational agent to update partial beliefs at minimal information gain consistent with the new evidence. The dissertation shows that information theory generalizes Bayesian norms and does not conflict with them. It also shows that the norms of information theory can only be defended when the agent entertains sharp credences. Many contemporary Bayesians permit indeterminate credal states for rational agents, which is incompatible with the norms of information theory. The dissertation then defends two claims: (1) the partial beliefs that a rational agent holds are formally expressed by sharp credences; and (2) when a rational agent updates these partial beliefs in the light of new evidence, the norms used are based on and in agreement with information theory. In the dissertation, I defuse a collection of counter-examples that have been marshaled against entropy principles. More importantly, building on previous work by others and expanding it, I provide a coherent and comprehensive theory of the use of information theory in formal epistemology. Information theory rivals probability theory in formal virtue, theoretical substance, and coherence across intuitions and case studies. My dissertation demonstrates its significance in explaining the doxastic states of a rational agent and in providing the right kind of normativity for them.

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