TRUTH IS EXPENDABLE: FOUNDATIONS FOR AN EMPIRICALLY INFORMED PHILOSOPHY OF TESTIMONY by Michael Wayne Hermon A dissertation submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Philosophy The University of Utah August 2011 Copyright © Michael Wayne Hermon 2011 All Rights Reserved The University of Utah Graduate School STATEMENT OF DISSERTATION APPROVAL The dissertation of Michael Wayne Hermon has been approved by the following supervisory committee members: Mariam Thalos , Chair 9 June 2011 Date Approved Stephen Downes , Member 12 June 2011 Date Approved Ronald Mallon , Member 9 June 2011 Date Approved Clifton McIntosh , Member 9 June 2011 Date Approved Richard Fowles , Member 9 June 2011 Date Approved and by Stephen Downes , Chair of the Department of Philosophy and by Charles A. Wight, Dean of The Graduate School. ABSTRACT The goal of this dissertation is to offer an empirically informed evaluation of testimony as a source of knowledge. Epistemologists have assumed that testimony is a generally reliable source of true beliefs because human cognitive faculties would have evolved to be reliable at getting the truth. However, complementary evidence from the signaling theory and social psychology literature shows that testimony is a practical tool with a variety of nonepistemic functions, including forming and maintaining social relationships, coordinating group behavior, and prescribing conduct. Since the value of using testimony is very often independent of its accuracy, humans have evolved to expend as little resources on checking for accuracy as is necessary to satisfy their other needs. In other words, “truth is expendable” to humans trying to get along well in the world and with each other. This implies that testimony is a far less epistemically reliable source of information than philosophers have assumed, and although it is very often prudent to simply believe what people say, it is not epistemically rational to do so. At the end, I offer preliminary empirically informed prescriptions for judging the reliability of testimony. TABLE OF CONTENTS ABSTRACT …..................................................................................................... iii ACKNOWLEDGMENTS ….............................................................................. vi CHAPTERS 1. INTRODUCTION …................................................................................. 1 The Goal ….......................................................................................................... 1 Chapter Summaries …...................................................................................... 4 PART I: THE PHILOSOPHICAL STUDY OF TESTIMONY …........................ 8 2. THE HISTORY OF THE EPISTEMOLOGY OF TESTIMONY ….......... 9 Skeptical Dismissals of Testimony…................................................................... 9 Hume's Reductionism ….................................................................................... 12 Reid's Nonreductionism …................................................................................ 13 Radical Translation and the Reliability of Testimony …................................... 17 3. THE NATURE OF TESTIMONY …....................................................... 22 Formal Testimony and Natural Testimony ….................................................... 22 “Testimony” as a Suitable Target of Epistemic Evaluation ….......................... 26 4. NONREDUCTIONISM …..................................................................... 28 Nonreductionism and the Default Rule …....................................................... 28 Introducing the Nonepistemic Uses of Testimony …...................................... 31 The Value of Shared Beliefs …........................................................................ 33 Default Acceptance and Memory ….................................................................. 35 5. REDUCTIONISM …............................................................................... 37 Hume's Reductionism ….................................................................................... 37 Global Reductionism …..................................................................................... 38 Objections to Global Reductionism …............................................................... 39 Epistemic Heterogeneity and Nonreductionism …............................................ 41 Statistical Local Reductionism …...................................................................... 43 Permissive Local Reductionism ….................................................................... 45 Conclusions …................................................................................................... 48 PART II: THE SCIENCE OF HUMAN COMMUNICATION ......................... 50 6. INTRODUCTION …................................................................................51 7. THE EVOLUTION OF HUMAN COMMUNICATION ….................... 54 Introduction …................................................................................................... 54 From Inferential Translation to Strategic Signaling …...................................... 55 Adaptive Signaling …........................................................................................ 60 The Evolution of Manipulation …..................................................................... 61 Signaling in Contexts of Coincident Interests …............................................... 62 Contexts of Noncoincident Interests …............................................................. 66 Conclusions …................................................................................................... 69 8. THE PSYCHOLOGY OF INFORMATION REGULATION …............. 73 Introduction …....................................................................................................73 Psychology and the Default Rule ….................................................................. 75 Motivation and Information Bias …...................................................................76 Ingroup Bias …...................................................................................................81 Group Bias In Young Children ….......................................................................84 Self-image Bias and Manipulation ….................................................................85 Confirmation Bias ….......................................................................................... 88 Conclusions …................................................................................................... 90 PART III: A NEW EPISTEMOLOGY OF TESTIMONY ….............................. 94 9. ACCURACY IS EXPENDABLE …....................................................... 95 Introduction …................................................................................................... 95 Conclusions: Epistemic Principles for Evolved Beings ................................... 96 Prescriptions: A Preliminary Empirically informed Philosophy of Testimony100 Future Research …........................................................................................... 106 BIBLIOGRAPHY ….......................................................................................... 108 v ACKNOWLEDGMENTS This dissertation would not have been possible without the unwavering support and confidence of Mariam Thalos. I will be forever grateful for her ongoing thoughtful encouragement. I would also like to acknowledge my darling partner, Ella, who's loving companionship and enthusiasm for my work provides me the motivation to develop and express important ideas. I would also like to thank the other members of my committee: Steve Downes, Ron Mallon, Clif McIntosh, and Richard Fowles for evaluating this research, and the Department of Philosophy and Graduate School at the University of Utah along with the National Science Foundation for invaluable financial support over the years. CHAPTER 1 INTRODUCTION The Goal The goal of this dissertation is to offer an empirically informed evaluation of testimony as a source of knowledge. Epistemologists have assumed that testimony is a generally reliable source of true beliefs because human cognitive faculties would have evolved to be reliable at getting the truth. However, complementary evidence from the signaling theory and social psychology literature shows that testimony is a practical tool with a variety of nonepistemic functions, including forming and maintaining social relationships, coordinating group behavior, and prescribing conduct. Since the value of using testimony is very often independent of its accuracy, humans have evolved to expend as little resources on checking for accuracy as is necessary to satisfy their other needs. In other words, “truth is expendable” to humans trying to get along well in the world and with each other. This implies that testimony is a far less epistemically reliable source of information than philosophers have assumed, and although it is very often prudent to simply believe what people say, it is not epistemically rational to do so. The prevailing view is that true beliefs are essential to good decision making and therefore adaptive, while holding false beliefs can result in poor decision making and are 2 therefore maladaptive. It is therefore common to assume that humans would have evolved cognitive practices