Truth, Semantic Closure, and Conditionals

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Truth, Semantic Closure, and Conditionals View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by D-Scholarship@Pitt TRUTH, SEMANTIC CLOSURE, AND CONDITIONALS by Shawn Standefer B.A., Stanford, 2006 M.A., Stanford, 2006 Submitted to the Graduate Faculty of the Kenneth P. Dietrich School of Arts and Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2013 UNIVERSITY OF PITTSBURGH KENNETH P. DIETRICH SCHOOL OF ARTS AND SCIENCES This dissertation was presented by Shawn Standefer It was defended on August 20, 2013 and approved by Anil Gupta, Department of Philosophy, University of Pittsburgh Nuel Belnap, Department of Philosophy, University of Pittsburgh Robert Brandom, Department of Philosophy, University of Pittsburgh James Shaw, Department of Philosophy, University of Pittsburgh Jeremy Avigad, Department of Philosophy, Carnegie Mellon University Dissertation Director: Anil Gupta, Department of Philosophy, University of Pittsburgh ii Copyright c by Shawn Standefer 2013 iii TRUTH, SEMANTIC CLOSURE, AND CONDITIONALS Shawn Standefer, PhD University of Pittsburgh, 2013 Almost all theories of truth place limits on the expressive power of languages containing truth predicates. Such theories have been criticized as inadequate on the grounds that these limitations are illegitimate. These criticisms set up several requirements on theories of truth. My initial focus is on the criticisms and why their requirements should be accepted. I argue that an adequate theory of truth should validate intuitive arguments involving truth and respect intuitive evaluations of the semantic statuses of sentences. From this starting point, I analyze the arguments in favor of several common requirements on theories of truth and formulate some minimal requirements on theories of truth. One is a logic neutrality requirement that says that a theory must be compatible with a range of logical resources, such as different negations. Another is the requirement that the theory validate certain laws governing truth, such as the T-sentences. These two requirements rule out many theories of truth. The main problem is that many theories lack an adequate conditional, the addition of which is, in fact, precluded by those theories. I argue that the revision theory of truth can satisfy my criteria when augmented with a pair of conditionals, which are defined using a modification of the framework of circular definitions of the revision theory. I distinguish two roles for conditionals in theories of truth and argue that the conditionals of the proposed theory fill those roles well. The conditionals are interdefinable with a modal operator. I prove a completeness theorem for the calculus C0 of The Revision Theory of Truth modified with rules for this operator. I examine the modal logic of this operator and prove a Solovay-type completeness theorem linking the modal logic and a certain class of circular definitions. iv I conclude by examining Field's recent theory of truth with its new conditional. I argue that Field's theory does not meet my requirements and that it fails to vindicate some of Field's own philosophical views. I close by proposing a framework for studying Field's conditional apart from his canonical models. v TABLE OF CONTENTS 1.0 THE PROBLEM OF SEMANTIC CLOSURE ..............1 1.1 Introduction..................................1 1.2 Three approaches to truth..........................5 1.3 Appeals to Semantic Closure........................ 12 1.4 Problems................................... 17 1.5 Projects.................................... 18 1.6 Languages and semantics.......................... 22 1.7 Hierarchies.................................. 25 1.7.1 Arithmetic.............................. 26 1.7.2 Sets.................................. 28 1.7.3 Semantics.............................. 29 1.8 Self-sufficiency................................ 32 1.8.1 First argument............................ 35 1.8.2 Second argument.......................... 36 1.8.3 Third argument........................... 36 1.8.4 Conclusions on semantic self-sufficiency.............. 37 1.9 Chapter summary.............................. 38 2.0 VERSIONS OF SEMANTIC CLOSURE .................. 39 2.1 Universality.................................. 39 2.1.1 Expressibility............................ 40 2.1.2 Extensibility............................. 42 2.1.3 Logic neutrality........................... 44 vi 2.1.4 Conclusions on universality..................... 47 2.2 Closure.................................... 47 2.2.1 Syntactic closure........................... 48 2.2.2 Semantic closure........................... 49 2.2.3 Predicates.............................. 51 2.2.4 Conclusions on closure....................... 53 2.3 Classification................................. 53 2.3.1 Kripke................................ 54 2.3.2 Field................................. 56 2.3.3 Beall................................. 58 2.3.4 Diagnosis............................... 60 2.3.5 Conclusions on classification.................... 63 2.4 Metalanguages................................ 64 2.4.1 Reinhardt.............................. 65 2.4.2 Priest on metalanguages...................... 66 2.4.3 No Richer Metalanguages...................... 67 2.4.4 Conclusions on metalanguages................... 71 2.5 Laws...................................... 71 2.6 Conclusions.................................. 75 3.0 CONDITIONALS AND REVISION THEORY .............. 77 3.1 Background.................................. 78 3.2 Connectives.................................. 80 3.2.1 Conditionals............................. 80 3.2.2 Box.................................. 84 3.2.3 Features............................... 85 3.3 Validity and related concepts........................ 92 3.4 Discussion................................... 94 3.4.1 Intersubstitutivity.......................... 95 3.4.2 Arguments.............................. 99 3.4.3 Inadequacy.............................. 101 vii 3.4.4 Neutrality.............................. 104 3.5 Determinateness............................... 106 3.6 Conclusion.................................. 112 4.0 EXPANDING THE REVISION THEORY ................ 114 4.1 Foundations.................................. 114 4.1.1 Similarity, hypotheses, and correspondence............ 115 4.1.2 Falling under hypotheses and the semantics of box........ 122 4.1.3 Extensions.............................. 123 4.1.4 Equality............................... 124 4.1.5 Revision............................... 126 4.1.6 Semantic substitution........................ 130 4.1.7 Definitions for revision theory................... 131 4.2 Soundness................................... 132 4.3 Completeness................................. 134 4.4 Finite definitions............................... 139 4.5 Revision indices................................ 144 5.0 THE MODAL LOGIC OF REVISION ................... 151 5.1 Modal logic.................................. 151 5.2 Solovay-type theorems............................ 169 5.2.1 Propositional Solovay-type theorem................ 170 5.2.2 First-order Solovay-type theorem.................. 176 5.2.3 Variations of Solovay-type theorems................ 180 6.0 FIELD'S THEORY ............................... 184 6.1 Background.................................. 184 6.2 Overview of Field's conditional....................... 188 6.2.1 General logic............................. 190 6.3 Negative features of Field's logic...................... 197 6.3.1 Responding to Gupta's criticisms................. 198 6.3.2 Artifacts and deflationism..................... 202 6.3.3 Truth-preservation.......................... 208 viii 6.4 Field's propositional logic.......................... 211 6.4.1 Short sequences........................... 218 6.4.2 Longer sequences.......................... 220 6.4.3 Even longer sequences........................ 221 6.5 Conclusions.................................. 224 7.0 CONCLUDING THOUGHTS ........................ 225 8.0 BIBLIOGRAPHY ................................ 229 ix LIST OF TABLES 1 Pattern of truth values across revisions..................... 173 2 Pattern of satisfaction across revisions...................... 174 3 Pattern of truth values across revisions..................... 175 4 Pattern of extensions for predicates across worlds................ 178 5 Pattern of extensions assigned by hypotheses.................. 178 6 Pattern of sets satisfied by hypotheses...................... 179 x LIST OF FIGURES 1 Corollary1..................................... 119 2 Lemma5...................................... 119 3 Lemma8...................................... 121 4 Lemma 10..................................... 121 5 Proof strategy for Solovay-type theorems.................... 171 xi 1.0 THE PROBLEM OF SEMANTIC CLOSURE 1.1 INTRODUCTION Truth seems to be a simple concept, one that is governed by principles of the form, pAq is true if and only if A where pAq is a name of the sentence A. These principles have come to be called T-sentences, or Tarski biconditionals. The collection of T-sentences for a language, together with classical logic and some modest syntactic resources results in triviality, so the set of naively interpreted T-sentences alone cannot be an adequate account of truth. There is a need to develop a theory of truth, an account of the logical and semantic features of truth. Truth easily gives rise to paradoxes, such as the liar paradox. A liar sentence is a sentence that says of itself that
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