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Desire, Belief, and Conditional Belief David Jeffrey Etlin

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Desire, Belief, and Conditional Belief David Jeffrey Etlin Desire, Belief, and Conditional Belief by M•MASSACHUSETTS INST!CTUTfj David Jeffrey Etlin OCT 1 2008 A.B., University of Chicago (1998) L BRARIES Submitted to the Department of Linguistics and Philosophy in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 2008 @David Etlin, 2008. The author hereby grants to MIT permission to reproduce and to distribute publicly paper and electronic copies of this thesis document in whole or in part in any medium now known or hereafter created. Author ............................... .......... ........... Department of Linguistics and Philosophy August 29, 2008 Certified by ............................... Robert Stalnaker Laurance S. Rockefeller Professor A hesis Supervisor Accepted by Chairman, Department Committee on Graduate Studies ARCHIVES Desire, Belief, and Conditional Belief by David Jeffrey Etlin Submitted to the Department of Linguistics and Philosophy on August 29, 2008, in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Philosophy Abstract This dissertation studies the logics of value and conditionals, and the question of whether they should be given cognitivist analyses. Emotivist theories treat value judgments as expressions of desire, rather than beliefs about goodness. Inference ticket theories of conditionals treat them as expressions of conditional beliefs, rather than propositions. The two issues intersect in decision theory, where judgments of expected goodness are expressible by means of decision-making conditionals. In the first chapter, I argue that decision theory cannot be given a Humean founda- tion by means of money pump arguments, which purport to show that the transitivity of preference and indifference is a requirement of instrumental reason. Instead, I ar- gue that Humeans should treat the constraints of decision theory as constitutive of the nature of preferences. Additionally, I argue that transitivity of preference is a stricter requirement than transitivity of indifference. In the second chapter, I investigate whether David Lewis has shown that deci- sion theory is incompatible with anti-Humean theories of desire. His triviality proof against "desire as belief' seems to show that desires can be at best conditional beliefs about goodness. I argue that within causal decision theory we can articulate the cognitivist position where desires align with beliefs about goodness, articulated by the decision making conditional. In the third chapter, I turn to conditionals in their own right, and especially iterated conditionals. I defend the position that indicative conditionals obey the import-export equivalence rather than modus ponens (except for simple conditionals), while counterfactual subjunctive conditionals do obey modus ponens. The logic of indicative conditionals is often thought to be determined by conditional beliefs via the Ramsey Test. I argue that iterated conditionals show that the conditional beliefs involved in indicative supposition diverge from the conditional beliefs involved in learning, and that half of the Ramsey Test is untenable for iterated conditionals. Thesis Supervisor: Robert Stalnaker Title: Laurance S. Rockefeller Professor Acknowledgments I am grateful to my friends and family for their support, especially Thao. I would like to thank everybody who I have learned from while at MIT, most of all my committee: Robert Stalnaker, Vann McGee and Agustin Rayo. Contents 1 Why Obey the Rationality Postulates? 1.1 Introduction ....................... 1.2 Humean versus Neo-Humean Theories of the Passions 1.3 Preference .. ....... .. .. .. ... .. ...... .. 14 1.3.1 Five Degrees of Preference Involvement .... .. ...... 14 1.3.2 Troubles With Negative Transitivity ..... .. .. .. .. 16 1.3.3 Fuzzy and Partial Rationality ......... ... ... 17 1.4 Choice and Choiceworthiness ..... ........ .. .. .. .. 18 1.4.1 From Buridan's Ass to Choice Functions . .. .. .. .. 18 1.4.2 Rationalizability ................ .. ... ... 20 1.4.3 Platitudes of Preference and Indifference . .. ... ... .. 21 1.5 Synchronic and Diachronic Path Independence . ... ... ... 23 1.5.1 "All Things Considered" ............ .. .. .. .. 23 1.5.2 Avoiding Cyclical Choice ............ .. .. .. 25 1.5.3 Worse Off With Cyclical Preferences? ... .. .. .. .. 27 1.5.4 Putting the Money Back in the Money Pump? . .. .. 28 1.5.5 Is it the Choice Rule? ............. .. .. .. .. 29 1.5.6 Money Pumps Without Cyclical Preferences . .. .. ... 31 1.5.7 Swapping Requirements versus Status-Quo Maintenance 1.5.8 Swapping Permission and Life-Planning .... .... .. 1.5.9 Moving Beyond Path Independence .. ... .. ... .. 1.6 Constitutive Constraints and Fragmented Minds .. ... .. .. 1.6.1 Where Reasons Come to an End .............. 1.6.2 Rational Choice Without Preferences? .. ..... .... 1.6.3 Comparison With Deductive Rationality .... ...... 1.6.4 Loading up the Consequences and Reflective Endorsement 1.7 Conclusion ... ..... ...... ..... ...... ..... 2 Cognitivism and Two Kinds of Desire 47 2.1 Introduction ............... .. ... ... .. ... ... 47 2.2 Beliefs About Goodness and Their Aligniment With Desire ...... 50 2.2.1 Cognitivism ........... ... ... .. ... ... .. 50 2.2.2 Externalism, Internalism, and Huimeanism . .......... 51 2.2.3 Absolutism versus Relativism . .. ... ... ... .. .. 53 2.3 The Setup and Proof of the Triviality R esult . ... ... ... .. .. 55 2.3.1 Background on the Formal Fram ework . ............ 56 2.3.2 Desire as Conditional Belief . .. .. ... .. .. .. .. 58 2.3.3 Desire as Belief ......... .. ... .. .. .. .. .. .. 59 2.3.4 The Triviality of Desire As Belief . .. .. .. .. .. 63 2.3.5 Comparison With Triviality for C:onditionals . ......... 63 2.3.6 Diagnosis: Conditionals and Negration .............. 65 2.4 Attempts to Save Cognitivism from the Triviality Theorem ...... 69 2.4.1 Qualms About the Decision Thec retic Idealizations ...... 70 2.4.2 Abandoning Belief for ConditionaL1 Belief . ............ 71 2.4.3 The Relativity of Value ..... .. .. .. .. .. .. .. ... 72 2.4.4 The Relativity of Indicative Condlitionals . ........... 73 2.5 Cognitivism Saved by Causal Conditiona ls . .. .. .. .. ... .. .. 75 2.5.1 From Evidential to Causal Decisi on Theory . ......... 76 2.5.2 Causal Decision Theory With Subjunctive Conditionals . 78 2.5.3 From Causal Decision Theory to Desire as Belief ... .. 81 2.5.4 A Newcomb Problem Around Every Corner .. .. .. 82 2.5.5 Choiceworthiness versus Desire .... .... .... .. 85 2.5.6 Rationalization and Two Kinds of Desire ...... ...... 2.5.7 Causal Utility as Motivating ................... 2.6 How un-Humean is Decision Theory? ... ........ ....... 3 Modus Ponens Revisited 3.1 Introduction ...................... .. ... .. .. 93 3.2 An Uncertain Inference ................ ... ... .... 94 3.2.1 The Main Example .............. ... .... .. 94 3.2.2 Some Lessons of the Example ........ S . .... ... 95 3.3 Analyses of the Indicative Conditional .... ... S . .. .. .. 96 3.3.1 The Material Conditional ... ....... S . .. .. ... 96 3.3.2 The Stalnaker Conditional .......... ... .. .. .. 97 3.3.3 The Hybrid Theory .............. .. .. ... .. 98 3.3.4 Conditional Probability and Adams' Thesis S . .. .. .. 100 3.4 The Import-Export Equivalence ........... .. ... .. .. 101 3.4.1 The Logic of Iterated Conditionals . .... S . ... .. 101 3.4.2 Modus Ponens as a Reasonable Inference . S .. ... .. .. 101 3.4.3 Trouble with Exportation .......... .. .. ... .. 103 3.4.4 Importation and the Direct Argument . .. S .. .. ... 105 3.4.5 The Supplemented Equivalence Theory . S . .. .. ... 107 3.5 Iterated Conditionals and the Ramsey Test ..... S . .. .. .. 109 3.5.1 Triviality for Simple Ramsey Test Condition als ........ 109 3.5.2 Conditional-Factual Dualism and Iterated Cc)nditionals . .. 111 3.5.3 Import-Export Triviality Results for Revisior s .......... 113 3.5.4 Lessons of the Iterated Triviality Results . .. .. .. ... 114 3.5.5 Semantics and Indexicalism .. .... ... .. .. .. .. 116 3.5.6 M odals ...... ....... ....... ....... .. 119 3.6 Subjunctive Conditionals ....................... 120 3.6.1 Extending the Analysis? . .... ... .... ... ... 120 3.6.2 Are There Subjunctive Counterexamples to Modus Ponens? 121 3.6.3 Counterfactual Counterexamples to Import-Export ...... 123 3.7 Conclusion ................ ....... .. ...... 125 10 Chapter 1 Why Obey the Rationality Postulates? 1.1 Introduction Decision theory is often taken to be a precise version of a view of practical reason attributed to Hume: values are subjective, and reasoning about them is instrumental. Yet it is generally noted that decision theory goes beyond what is officially sanctioned by Hume, in that it places structural constraints on preferences where Hume did not find any. In a famous discussion of the subjectivity of the "passions", Hume says: 'Tis not contrary to reason to prefer the destruction of the whole world to the scratching of my finger. (A Treatise of Human Nature II.III.III "Of the Influencing Motives of the Will") According to the requirement of transitivity, Hume should grant that if he also prefers the scratching of his finger to the brushing of his hair, then it is contrary to reason for him to fail to prefer to the destruction of the world to the brushing of his hair. Hume nowhere concedes such a requirement, and explicitly denies that there are any rational constraints on passions other than what are imposed by causal beliefs in means-ends reasoning. Indeed,
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