Anthropic Bias: Observation Selection Effects in Science and Philosophy

237 Pages·2001·1.719 MB·English

by  Nick Bostrom

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A B
NTHROPIC IAS
Observation Selection Effects in Science
and Philosophy
Nick Bostrom
Routledge
New York & London
01 Front Matter (i-vi) 6/4/02 10:37 AM Page iv
Published in 2002 by
Routledge
29 West 35th Street
New York,NY10001
Published in Great Britain by
Routledge
11 New Fetter Lane
London EC4P 4EE
Routledge is an imprint of the Taylor & Francis Group
Printed in the United States of America on acid-free paper.
Copyright © 2002 by Nick Bostrom
All rights reserved.No part of this book may be reprinted or reproduced or
utilized in any form or by any electronic,mechanical,or other means,now
known or hereafter invented,including photocopying and recording,or in any
information storage or retrieval system,without permission in writing from the
publisher.
10 9 8 7 6 5 4 3 2 1
Library of Congress Cataloging-in-Publication Data
Bostrom,Nick,1973–
Anthropic bias :observation selection effects in science and philosophy / by
Nick Bostrom.
p.cm.— (Studies in philosophy)
Includes bibliographical references and index.
ISBN0-415-93858-9
1.Methodology. 2.Anthropic principle. 3.Selectivity (Psychology)
4.Observation (Scientific method) I.Title. II.Studies in philosophy (New York,
N.Y.)
BD241.B657 2002
121'.6—dc21 2001058887
01 Front Matter (i-vi) 6/4/02 10:37 AM Page v
This book is dedicated to my father—tack pappa!

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Contents
ACKNOWLEDGEMENTS xi
PREFACE xiii
CHAPTER1
INTRODUCTION 1
Observation selection effects 1
A brief history of anthropic reasoning 5
Synopsis of this book 7
CHAPTER2
FINE-TUNING IN COSMOLOGY 11
Does fine-tuning need explaining? 13
No “Inverse Gambler’s Fallacy” 16
Roger White and Phil Dowe’s analysis 18
Surprising vs. unsurprising improbable events 23
Modeling observation selection effects: the angel parable 32
Preliminary conclusions 39
CHAPTER3
ANTHROPIC PRINCIPLES: THE MOTLEY FAMILY 43
The anthropic principle as expressing an observation
selection effect 43
Anthropic hodgepodge 46
Freak observers and why earlier formulations are inadequate 51
The Self-Sampling Assumption 57
vii
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viii Contents
CHAPTER4
THOUGHT EXPERIMENTS SUPPORTING THE
SELF-SAMPLING ASSUMPTION 59
The Dungeon gedanken 59
Two thought experiments by John Leslie 62
The Incubatorgedanken 64
The reference class problem 69
CHAPTER5
THE SELF-SAMPLING ASSUMPTION IN SCIENCE 73
SSA in cosmology 73
SSA in thermodynamics 76
SSA in evolutionary biology 78
SSA in traffic analysis 82
SSA in quantum physics 84
Summary of the case for SSA 86
CHAPTER6
THE DOOMSDAY ARGUMENT 89
Background 89
Doomsayer Gott 90
The incorrectness of Gott’s argument 92
Doomsayer Leslie 94
The premisses of DA, and the Old evidence problem 96
Leslie’s views on the reference class problem 104
Alternative conclusions of DA 107
CHAPTER7
INVALID OBJECTIONS AGAINST THE DOOMSDAY ARGUMENT 109
Doesn’t the Doomsday argument fail to
“target the truth”? 109
The “baby-paradox” 111
Isn’t a sample size of one too small? 115
Couldn’t a Cro-Magnon man have used the
Doomsday argument? 116
We can make the effect go away simply by considering
a larger hypothesis space 116
Aren’t we necessarily alive now? 118
Sliding reference of “soon” and “late”? 119
How could I have been a 16th century human? 119
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Contents ix
Doesn’t your theory presuppose that what happens in causally
disconnected regions affects what happens here? 120
But we know so much more about ourselves than
our birth ranks! 120
The Self-Indication Assumption—
Is there safety in numbers? 122
CHAPTER8
OBSERVER-RELATIVE CHANCES IN ANTHROPIC REASONING? 127
Leslie’s argument, and why it fails 127
Observer-relative chances: another go 130
Discussion: indexical facts—no conflict with physicalism 132
In conclusion 136
Appendix: the no-betting results 137
CHAPTER9
PARADOXES OF THE SELF-SAMPLING ASSUMPTION 141
The Adam & Eve experiments 142
Analysis of Lazy Adam: predictions and counterfactuals 144
++
The UN gedanken: reasons and abilities 150
Quantum Joe: SSA and the Principal Principle 154
Upshot 156
Appendix: The Meta-Newcomb problem 157
CHAPTER10
OBSERVATION SELECTION THEORY: A METHODOLOGY FOR
ANTHROPIC REASONING 159
Building blocks, theory constraints and desiderata 159
The outline of a solution 161
SSSA: Taking account of indexical information of observer-
moments 162
Reassessing Incubator 165
How the reference class may be observer-moment relative 168
Formalizing the theory: the Observation Equation 172
A quantum generalization of OE 174
Non-triviality of the reference class: why (cid:1)0must be rejected 175
A subjective factor in the choice of reference class? 181
CHAPTER11
OBSERVATION SELECTION THEORY APPLIED 185
Cosmological theorizing: fine-tuning and freak observers 185
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The freak-observer problem places only lax demands on
the reference class 193
The Sleeping Beauty problem: modeling imperfect recall 194
The case of no outsiders 195
The case with outsiders 196
Synthesis of the 1⁄- and the 1⁄-views 198
2 3
Observation selection theory applied to other scientific problems 198
Robustness of reference class and scientific solidity 202
Wrap-up 204
BIBLIOGRAPHY 207
INDEX 219