Choice and Credence in Context
McNamara, Calum
2024
Abstract
This dissertation is about the role that conditionals play in uncertain reasoning and deliberation. Specifically, I attempt to show that, by appealing to a particular semantics for conditionals---a contexutalist, sequence semantics, which has recently become popular in philosophy of language---several open problems in decision theory and epistemology can be solved. Chapter 1 is introductory. I set out the semantic view of conditionals in question, and I describe some of its historical background. Chapter 2 turns to a striking problem faced by causal decision theorists. A popular formulation of causal decision theory (CDT) appeals to counterfactual conditionals. However, the standard theory of these conditionals has unintuitive consequences in deterministic worlds. In particular, it says that if anything---including the choice you make---were different in the present, then either the laws or nature would be violated, or the distant past would be changed. And as several authors have recently shown, it's easy to transform this consequence of the standard theory of counterfactuals into full-blown counterexamples to CDT. In response to these counterexamples, I develop a contextualist version of CDT, which makes use of the sequence semantics. I then show that the deterministic counterexamples don't arise for my version of CDT. In Chapter 3, I deal with a different puzzle, about whether or not the so-called Desire-as-Belief (DAB) thesis is consistent with decision theory---something that famous arguments of David Lewis seem to show isn't the case. Once again, I show that, if we understand the DAB thesis in a contextualist way---and spell it out using the sequence semantics---then Lewis's arguments against that thesis don't go through. In fact, we can prove a tenability result for the DAB thesis, which shows that it's compatible with decision theory after all. Finally, in Chapter chapter_4, I transition from decision-theoretic issues to epistemological ones. More precisely, I tackle the question of how our credences should change when we learn indicative conditionals. Several famous cases in the literature---notably, Bas van Fraassen's Judy Benjamin problem---seem to show that the standard Bayesian update rules deliver implausible results when we learn conditionals of this kind. However, in the chapter, I show that, if we adopt the sequence semantics, then the Bayesian update rules turn out to deliver the correct results after all. Better still, alternatives to these rules which have been put forward in the literature turn out to be equivalent to the Bayesian rules in my framework---at least in many contexts. Thus, what we end up with is a nice, unified account of how rational agents should update on conditional information: one which fits in well with recent work on the semantics of conditionals. My proposal also relates, in interesting ways, to discussions that have been happening elsewhere in the literature, like discussions about the tenability of the notorious Stalnaker's thesis.Deep Blue DOI
Subjects
The role of conditionals in decision theory and epistemology
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Thesis
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