ROY A. SORENSEN THOUGHT EXPERIMENTS Thispage intentionally !efi blank THOUGHT EXPERIMENTS ROY A. SORENSEN OXFORD UNIVERSITY PRESS New York Oxford Oxford University Press Oxford New York Athens Auckland Bangkok Bogota Buenos Aires Calcutta Cape Town Chennai Dar es Salaam Delhi Florence Hong Kong Istanbul Karachi Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi Paris Săo Paulo Singapore Taipei Tokyo Toronto Warsaw and associated companies in Berlin lbadan Copyright © 1992 by Roy A. Sorensen First published in 1992 by Oxford University Press, Inc. 198 Madison Av enue, New York, New York 10016 First Issued as an Oxford University Press paperback, 1998 Oxford is a registered trademark of Oxford University Press, !ne. AU rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Sorensen, Roy A. Thought expriments Roy A. Sorensen p. cm. Includes bibliographica1 references and index. ISBN 0-19-507422-X ISBN 0-19-512913-X (pbk.) 1 Thought and thinking. 2. Logic 3. Philosophy and science 1. Title B105.T54S67 1992 !01-dc20 9136760 1357 986 42 Printed in the United States of America on acid-free paper For Julia, a woman of fine distinctions Thispage intentionally !efi blank ACKNOWLEDG MENTS This book has indebted me to many people. The first group consists of the individuals who attended colloquia given at the Graduate Center of the City University of New Yo rk, Columbia University, Dartmouth College, Rutgers University, the State University of New Yo rk at Stony Brook, Virginia Tech, and the 1990 lnter-University Conference for Philosophy of Science in Du­ brovnik. Severa! of my colleagues at New Yo rk University have earned my gratitude for their encouragement and advice, among them Raziel Abelson, Frances Kamm, John Richardson, William Ruddick, Peter Unger, and espe­ cially J ohn Carroll. 1 have also acquired far-flung debts to Lars Bergstrom, J ames Robert Brown, and Martin Bunzl, who scrutinized earlier drafts. Since 1 used the latter in philosophy of science courses, this book has benefited from student input. Anonymous, detailed referee reports led me to make painful but necessary excisions, precisifications and elaborations. This book has been through enough drafts to win rave reviews from lumberjacks! A New Yo rk University presidential Fellowship allowed me to experience the hospitality of the Virginia Tech philosophy department. Richard Burian guided me through the ins and outs of evolutionary theory and philosophy of biology (though 1 may still have zigged where 1 should have zagged); Joseph Pitt was my Galileo hotline; Peter Barker and Roger Ariew filled in assorted gaps in my knowledge of the history of science; and John Christman, Julia Driver, and Jim Klagge kept me in focus about ethical thought experiments. My last group of creditors are editors. 1 thank the editor of the American Scientist for permission to use a portion of "Thought Experiments" in chapters 3 and 6 and the editors of Philosophical Studies for the use of parts of "Moral Dilemmas, Thought Experiments, and Conflict Vagueness" in chapter 7. Fi­ nally, at Oxford University Press 1 thank senior editor Cynthia Read and assistant editor Peter Ohlin for shepherding this book into its final form. New York R.A.S. September 1991 Thispage intentionally !efi blank CONTENTS Introduction, 1 1. Our Most Curious Device, 3 I The Instrument of Choice, 7 II Scientific Thought Experiments, 8 III The Bridge to Philosophical Thought Experiments, 11 IV Analytic Philosophy's Commitment to Thought Experiment, 15 2. Scepticism About Thought Experiments, 21 I Introspection on the Sly? 21 A. The Interna! Horizon, 21 B. Complaints About Introspection, 22 C. The Parallel Plight of Thought Experiments, 26 II A Repackaged Appeal to Ordinary Language? 41 A. How the Appeal to Ordinary Language Is Supposed to Wo rk, 42 B. Strong Scepticism About the Appeal to Ordinary Language, 42 C. Moderate Scepticism About the Appeal to Ordinary Language, 43 D. Semantic Descent to Thought Experiments, 45 III Thought Experiments and the Dilemma of Informativeness, 46 3. Mach and Inner Cognitive Africa, 51 I Instinctive Knowledge, 51 II The Continuum of Cognitive Bargain Hunters, 58 III Mach's Response to the Problem of Informativeness, 61 X CONTENTS IV Appraisal of Mach, 63 A. What Mach Got Right, 63 B. What Mach Got Wrong, 67 4. The Wonder of Armchair Inquiry, 76 I The Pseudoanomaly, 76 A. Modal Gap Illusions, 77 B. How Thought Experiments Yield Modal Conclusions, 79 II Positive Theories of Armchair Inquiry, 88 A. The Recollection Model, 88 B. The Transformation Model, 92 C. The Homuncular Model, 95 D. The Rearrangement Model, 99 III The Cleansing Model, 104 A. How Thought Experiment Corrects Imbalances, 104 B. Theoretical and Practica! Irrationality, 106 IV An Eclectic View of the Mechanics of Thought Experiment, 109 5. Kuhntradictions, III I Kuhn on the Received Opinion, 111 II Misfits, 112 III The Left Hand of Logic, 114 IV Truth or Dare? 116 A. The Incoherence of Incoherent Concepts, 116 B. Violation of Logica! Conservatism, 119 V Reconstruction of Kuhn's Error, 122 A. The Guts of Paradox, 122 B. Conflationary Factors, 123 C. The Phenomenology of Inconsistency, 127 D. Counteranalysis of Kuhn's Cases, 128 E. Taxonomie Prospects, 130 6. The Logical Structure of Thought Experiment, 132 I Attributing Thought Experiments, 132 II Thought Experiments as Alethic Refuters, 135 A. Necessity Refuters, 135 B. The Five Responses to the Quintet, 136 CONTENTS XI C. Summary of Necessity Refuters, 152 D. Possibility Refuters, 153 E. Summary of Possibility Refuters, 159 III The Identity Conditions for Thought Experiments, 160 IV An Extension to Ordinary Experiments, 164 V The Big Picture, 165 7. Conflict Vagueness and Precisification, 167 I General Features of Vagueness, 167 II Dueling Definitions, 168 A. The Psychology of Conflict Vagueness, 168 B. How Conflict Vagueness Creates the Mirage of Local Incoherence, 170 C. Extensional Conflict Vagueness, 171 D. Intensional Conflict Vagueness, 172 III Application of the Quintet Schema, 174 IV Conceptual Reform, 175 V Eliminative Reactions to Conflict Vagueness, 180 VI Tolerating the Vagueness, 180 VII Extending the Analysis, 181 VIII Sunder, Enlighten! 184 8. The Evolution of Thought Experiment, 186 I 'Experiment' Defined, 186 A. Stereotypical Features of Experiment, 186 B. A Cognitive Aim Is Essential to Experiment, 189 II Execution Is an Optional Part of Experiment, 190 III The Progression from Experiment to Thought Experiment, 192 IV Classifying Thought Experiments by Grounds for Inaction, 197 A. Unimprovables, 197 B. Unaffordables, 199 C. Impossibles, 200 V The Immigration of the Supposition Operator, 202 VI A Definition of 'Thought Experiment', 205 A. The Selectivity of the Definition, 206 B. Stereotypical Features of Thought Experiments, 208 VII Ve rbal Disputes over 'Thought Experiment', 210 VIII Five Theses Recapitulated, 212 X Il CONTENTS 9. Are Thought Experiments Experiments? 216 I Systematically Misleading Expressions, 216 II Comparisons with Lookalikes, 218 A. Imaginary Experiments, 218 B. Fictional Experiments, 222 c. Mythical Experiments, 224 D. Models, Simulations, Reenactments, 225 III The Analogy with Ordinary Experiments, 228 A. The Taxonomie Point of the Analogy, 229 B. Points of Resemblance, 230 c. Points of Difference, 241 D. Bogus Points of Difference, 248 IV A Lopsided Tally, 250 10. Fallacies and Antifallacies, 252 I The Biologica! Baseline, 252 II Myths and Abuses, 254 III Fallacious Thought Experiments, 256 A. Missupposition, 257 B. Perspectiva! Illusions, 259 C. Framing Effects, 261 D. Biases of Thought Experiment, 261 E. Jumping the If/ Ought Gap, 269 F. Overweighting Negative Thought Experiments, 271 G. The Additive Fallacy, 272 H. The Blindspot Fallacy, 273 IV Antifallacies, 274 A. General Characterization of Antifallacies, 274 B. The Far Out Antifallacy, 277 C. Strangeness In, Strangeness Out? 284 D. The Vo yeur Antifallacy, 285 E. The Kabuki Antifallacy, 286 V A Parting Comparison, 288 Notes, 291 Select Bibliography, 307 Subject Index, 311 N ame Index, 315 THOUGHT EXPERIMENTS Given a sufficient constancy of environment, there is developed a correspond­ ing constancy of thought. By virtue of this constancy aur thoughts are spontaneously impelled to complete ali incompletely observed facts. The impulse in question is not prompted by the individual facts as observed at the time; nor is it intentionally evoked; but we find it operative in ourselves entirely without our personal intervention.. .. By this impulse we have always a larger portian of nature in aur field of vision than the inexperienced man has, with the single fact alone.For the human being, with his thoughts and impulses, is himself merely a piece of nature, which is added to the single fact.... When an electric current flows round a magnetic needle situated in its plane, the north pole of the needle is deflected to my left. I imagine myself as Ampere's swimmer in the current. I enrich the fact (current and needle) which is insufficient in itself to define the direction of my thought, by introducing myself into the experiment by an inner reaction. Ernst Mach I am a little piece of nature. Albert Einstein Introduction This book presents a general theory of thought experiments: what they are; how they work; their virtues and vices. Since my aim is synoptic, a wide corpus of thought experiments has been incorporated. There is a special abundance of examples from ethics and the metaphysics of personal identity because thought experiments in these areas have recently attracted heavy commentary. But the emphasis is on variety, rather than quantity. Thus, the discussion ranges over thought experiments from many disparate fields, from aesthetics to zoology. Scientific thought experiments-especially those in physics-are the clear cases, so my primary goal is to establish true and interesting generalizations about them.