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Quantum Philosophy ✣ This page intentionally left blank Quantum Philosophy UNDERSTANDING AND INTERPRETING CONTEMPORARY SCIENCE ✣ OLAND MN S R O f Translated by Arturo Sangalli PRINCETON UNIVERSITY PRESS PRINCETON, NEW JERSEY Copyright1999byPrincetonUniversityPress PublishedbyPrincetonUniversityPress,41WilliamStreet, Princeton,NewJersey08540 IntheUnitedKingdom:PrincetonUniversityPress, Chichester,WestSussex TranslatedfromtheFrencheditionofRolandOmnès, Philosophiedelasciencecontemporaine (Paris:EditionsGallimard,1994) AllRightsReserved LibraryofCongressCataloging-in-PublicationData Omnès,Roland [Philosophiedelasciencecontemporaine.English] Quantumphilosophy:understandingandinterpretingcontemporary science/RolandOmnès;translatedbyArturoSangalli. p. cm. Includesbibliographicalreferencesandindex. ISBN0-691-02787-0(cl.:alk.paper) 1.Physics—Philosophy. 2.Mathematics—Philosophy. 3.Science—Philosophy. 4.Quantumtheory. I.Title. QC6.055 1999 530′.01—dc21 98-42445 PublishedwiththeassistanceoftheFrenchMinistryofCulture ThisbookhasbeencomposedinSabon Thepaperusedinthispublicationmeetstheminimumrequirements ofANSI/NISOZ39.48-1992(R1997)(PermanenceofPaper) http://pup.princeton.edu PrintedintheUnitedStatesofAmerica 1 3 5 7 9 10 8 6 4 2 Contents ✣ ✣ Preface xi Acknowledgments xiii Prelude xv PARTONE THELEGACY 1 CHAPTER I Classical Logic 6 Pythagoras and thePariah 7 Plato and theLogos 10 The Logic of Aristotle and of Chrysippus 12 The Paradoxes 16 Two Useful Notions 19 The Universals 20 CHAPTER II Classical Physics 23 Astronomy, from Hipparchus to Kepler 23 The Dawn of Mechanics 28 Newton’s Dynamics 31 Wavesin theEther 36 The Beginning of Electromagnetism 39 A Turning Point: Maxwell’s Equations 41 CHAPTER III Classical Mathematics 47 Classical Mathematics 47 Rigor and Profusion in theNineteenth Century 53 Mathematicsand Inﬁnity 58 CHAPTER IV Classical Philosophy of Knowledge 62 Francis Bacon and Experience 62 Descartesand Reason 64 Locke and Empiricism 66 CONTENTS Digression: Cognition Sciences 67 Hume’sPragmatism 69 Kant 71 PARTTWO THEFRACTURE 79 CHAPTER V Formal Mathematics 84 The Ageof Formalism 84 Formal Logic 86 Symbols and Sets 88 Propositions 91 Some Remarks Regarding Truth 93 Taming Inﬁnity 97 Today’s Mathematics 100 The Crisis in theFoundations of Set Theory 102 Gödel’s Incompleteness Theorem 105 A TentativeConclusion 107 CHAPTER VI The Philosophy of Mathematics 108 What Is Mathematics? 108 MathematicalRealism 111 Nominalism 116 MathematicalSociologism 118 Mathematicsand Physical Reality 121 CHAPTER VII Formal Physics 124 The Century of Formal Physics 124 Relativity 126 The RelativisticTheory of Gravitation 130 The Prehistory of theAtom 134 Classical Physics in a Straitjacket 138 The Assassination of Classical Physics 140 The Harvestof Results 144 CHAPTER VIII The Epistemology of Physics 147 Why Do We Need Interpretation? 148 vi CONTENTS Uncertainties 150 The Principle of Complementarity 152 The Reduction of theWave Function 155 PARTTHREE FROMFORMALBACKTOVISUAL: THEQUANTUMCASE 159 CHAPTER IX BetweenLogic and Physics 163 The Outline of a Program 163 The Logic of Common Sense 165 Classical Dynamics and Determinism 168 With theHelp of an Angel 170 Observables 173 Rudiments of a Quantum Dialect 174 Histories 177 The Role of Probabilities 178 The Logic of theQuantum World 180 Complementarity 181 A Logical Law of Physics 182 CHAPTER X Rediscovering Common Sense 184 The World on a Large Scale 184 The Logic of Common Sense 186 Determinism 190 A First Philosophical Survey 193 CHAPTER XI From the Measurable to the Unmeasurable 196 The Poignant Problem of Interferences 196 The DecoherenceEffect 199 The Wonders of Decoherence:Physical 202 The Wonders of Decoherence:Logical 204 Last Wonders: TheDirection of Time 207 MeasurementTheory 208 WaveFunction Reduction Revisited 209 The Chasm 211 Addendum 215 vii CONTENTS CHAPTER XII On Realism 216 A Brief History of Realism 216 Quantum Physics and Realism 221 Ordinary Reality 223 Rationality versus Realism 224 The “EPR” Experiment 225 Bell and Aspect 227 Controversies about Histories 230 Toward a Wider Realism 233 PARTFOUR STATEOFTHEQUESTIONANDPERSPECTIVES 235 CHAPTER XIII A New Beginning 237 A Preliminary Report 237 The Beginnings of a Philosophy 239 The Religious Temptationand theSacred 241 CHAPTER XIV What Is Science? 246 Scienceas Representation 246 On Certain Typesof Laws 248 The Transformations of Science 250 Thomas Kuhn 252 CHAPTER XV Method 255 A Method for Judging, Not for Building 255 Which Method? 256 A Four-Stage Method 257 The Natureof theFour Stages 260 The Lesson of theFailed Attempts 261 Method and theSocial Sciences 262 Consistency and Beauty 264 The Flexibility of Principles 266 The Thing in theWorld Most Evenly Distributed 267 viii CONTENTS CHAPTER XVI Vanishing Perspectives 269 The Theory of Knowledge 269 Logos 271 The Instauration 273 Founding Science 278 Glossary 283 NameIndex 291 Subject Index 295 ix