Clarendon Library Of Logic and Philosophy Gerneral Editor:L.Jonathan Cohen The Scientic Image The Clarendon Library of Logic and Philosophy brings together books, by new as well as by established authors, that combine originality of theme with rigour of statement. Its aim is to encourage new research of a professional standard into problems that are of current or perennial interest. Also published in this seriesPhilosophy without Ambiguity by Jay David Atlas Quality and Concept by George Bealer Psychological Models and Neural Mechanisms by Austen Clark The Probable and the Provable by L. Jonathan Cohen The Diversity of Moral Thinking by Neil Cooper The Metaphysics of Modality by Graeme Forbes The Logic of Aspect: An Axiomatic Approach by Anthony Galton Ontological Economy by Dale Gottlieb Experiences: An Inquiry into some Ambiguities by J. M. Hinton The Fortunes of Inquiry by N. Jardine Metaphor: Its Cognitive Force and Linguistic Structure by Eva Feder Kittay The Cement of the Universe: A Study of Causation by J. L. Mackie Divine Commands and Moral Requirements by P. L. Quinn Rationality: A Philosophical Inquiry into the Nature and the Rationale of Reason by Nicholas Rescher Simplicity by Elliot Sober Blindspots by Roy N. Sorenson The Coherence of Theism by Richard Swinburne Anti-Realism and Logic: Truth as Eternal by Neil Tennant The Emergence of Norms by Edna Ullmann-Margalit Ignorance: A Case for Scepticism by Peter Unger The Matter of Minds by Zeno Vendler Chance and Structure: An Essay on the Logical Foundations of Probability by John M. Vickers What is Existence? by C. J. F. Williams Works and Worlds of Art by Nicholas Wolterstorff The Scientic Image Bas C. van Fraassen CLARENDON PRESS · OXFORD Great Clarendon Street, Oxford OX2 6DP Oxford University Press is a department of the University of Oxford It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide in Oxford New York Auckland Bangkok Buenos Aires Cape Town Chennai Dar es Salaam Delhi Hong Kong Istanbul Karachi Kolkata Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi São Paulo Shanghai Taipei Tokyo Toronto Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., New York © Bas C. van Fraassen 1980 The moral rights of the authors have been asserted Database right Oxford University Press (maker) First published 1980 All rights reserved. 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Title 501 Q175 79–42793 ISBN 0-19-824427-4 To the friendly people of Tigh-na-Coille This page intentionally left blank Preface The aim of this book is to develop a constructive alternative to scientific realism, a position which has lately been much discussed and advocated in philosophy of science. To this end, I shall present three theories, which need each other for mutual support. The first concerns the relation of a theory to the world, and especially what may be called its empirical import. The second is a theory of scientific explanation, in which the explanatory power of a theory is held to be a feature which does indeed go beyond its empirical import, but which is radically context-dependent. And the third is an explication of probability as it occurs within physical theory (as opposed to: in the evaluation of its evidential support). The first two chapters form a brief and relatively popular introduction to the debates concerning scientific realism, and will thereby explain the organization and strategy of the remainder. I have kept the exposition non- technical throughout, referring for technical details to journal articles where they seem to me more rightfully to belong. My debts are numerous; many of them will be clear from the notes. I would like to add here a few personal acknowledgements. My greatest debt in philosophy of science has always been to Adolf Grünbaum: this debt was renewed when I attended his lecture on Dirac's electrodynamics at Santa Margharita in 1976, a paradigm of philosophical exposition of science which I can scarcely hope to emulate. To Glymour, Hooker, Putnam, Salmon, Smart, and Sellars I owe the debt of the challenge of their philosophical positions and their willingness to discuss them with me, both on public occasions and in personal correspondence. The title of this book is a phrase of Wilfrid Sellars's, who contrasts the scientific image of the world with the manifest image, the way the world appears in human observation. While I would deny the suggestion of dichotomy, the phrase seemed apt. Toraldo di Francia gave me the opportunity to take part in the Fermi Institute Summer School on Foundations of Physics in Varenna, where I learned a great deal, not least from his and Dalla Chiara's lectures on their theory of the structure of physics. An older debt recalled in writing various parts of this book is to Henry Margenau, from whom I learned much about probabilities viii PREFACE and states in quantum mechanics. Many friends and colleagues helped at various stages during the writing of this book by reacting, at once sympathetically and ruthlessly, to my arguments, ideas, and didactic stories; Paul Benacerraf, Nancy Cartwright, Ronald de Sousa, Hartry Field, Yvon Gauthier, Ronald Giere, Karel Lambert, Edwin Levy, Margot Livesey, Hugh Mellor, Ben Rogers, Richmond Thomason, and Roger Woolhouse, to mention only a few. The main theses of this book were presented in lectures at a number of occasions, the last before press being three lectures at Princeton University in May 1979. Finally, the aid of the Canada Council in support of the research projects during which this book took shape was invaluable, especially in facilitating the contacts with other scholars necessary for that research. B. C. v. F. July, 1979 Contents 1. INTRODUCTION 1 2. ARGUMENTS CONCERNING SCIENTIFIC REALISM 6 §1. Scientific Realism and Constructive Empiricism 6 §1.1 Statement of Scientific Realism 6 §1.2 Alternatives to Realism 9 §1.3 Constructive Empiricism 11 §2. The Theory/Observation ‘Dichotomy’ 13 §3. Inference to the Best Explanation 19 §4. Limits of the Demand for Explanation 23 §5. The Principle of the Common Cause 25 §6. Limits to Explanation: a Thought Experiment 31 §7. Demons and the Ultimate Argument 34 3. TO SAVE THE PHENOMENA 41 §1. Models 41 §2. Apparent Motion and Absolute Space 44 §3. Empirical Content of Newton's Theory 46 §4. Theories and their Extensions 47 §5. Extensions: Victory and Qualified Defeat 50 §6. Failure of the Syntactic Approach 53 §7. The Hermeneutic Circle 56 §8. Limits to Empirical Description 59 §9. A New Picture of Theories 64 4. EMPIRICISM AND SCIENTIFIC METHODOLOGY 70 §1. Empiricist Epistemology and Scepticism 71 §2. Methodology and Experimental Design 73 §2.1 The Roles of Theory 73 §2.2 Measuring the Charge of the Electron 74 §2.3 Boyd on the Philosophical Explanation of Methodology 77 §2.4 Phenomenology of Scientific Activity 80 §3. The Conjunction Objection 83 x CONTENTS §4. Pragmatic Virtues and Explanation 87 §4.1 The Other Virtues 87 §4.2 The Incursion of Pragmatics 89 §4.3 Pursuit of Explanation 92 5. THE PRAGMATICS OF EXPLANATION 97 §1. The Language of Explanation 97 §1.1 Truth and Grammar 97 §1.2 Some Examples 101 §2. A Biased History 103 §2.1 Hempel: Grounds for Belief 103 §2.2 Salmon: Statistically Relevant Factors 106 §2.3 Global Properties of Theories 109 §2.4 The Difficulties: Asymmetries and Rejections 111 §2.5 Causality: the Conditio Sine Qua Non 112 §2.6 Causality: Salmon's Theory 118 §2.7 The Clues of Causality 123 §2.8 Why-questions 126 §2.9 The Clues Elaborated 129 §3. Asymmetries of Explanation: A Short Story 130 §3.1 Asymmetry and Context: the Aristotelian Sieve 130 §3.2 ‘The Tower and the Shadow’ 132 §4. A Model for Explanation 134 §4.1 Contexts and Propositions 134 §4.2 Questions 137 §4.3 A Theory of Why-questions 141 §4.4 Evaluation of Answers 146 §4.5 Presupposition and Relevance Elaborated 151 §5. Conclusion 153 6. PROBABILITY: THE NEW MODALITY OF SCIENCE 158 §1. Statistics in General Science 159 §2. Classical Statistical Mechanics 161 §2.1 The Measure of Ignorance 161 §2.2 Objective and Epistemic Probability Disentangled 164 §2.3 The Intrusion of Infinity 167 §3. Probability in Quantum Mechanics 169 §3.1 The Disanalogies with the Classical Case 170 CONTENTS xi §3.2 Quantum Probabilities as Conditional 175 §3.3 Virtual Ensembles of Measurements 177 §4. Towards an Empiricist Interpretation of Probability 178 §4.1 Probability Spaces as Models of Experiments 178 §4.2 The Strict Frequency Interpretation 181 §4.3 Propensity and Virtual Sequences 187 §4.4 A Modal Frequency Interpretation 190 §4.5 Empirical Adequacy of Statistical Theories 194 §5. Modality: Philosophical Retrenchment 196 §5.1 Empiricism and Modality 196 §5.2 The Language of Science 198 §5.3 Modality without Metaphysics 201 7. GENTLE POLEMICS 204 NOTES 216 INDEX 231 This page intentionally left blank 1 Introduction [I]t is easy to indulge the commonplace metaphysical instinct.