Ockham’s Razors: A User’s Manual

325 Pages·2015·2.133 MB·English

by  Elliott Sober

Ockham’sRazors
Ockham’srazor,theprincipleofparsimony,statesthatsimplertheoriesare
betterthantheoriesthataremorecomplex.Ithasahistorydatingbackto
Aristotle,anditplaysanimportantroleincurrentscience.Therazoralso
getsusedineverydaylifeandinphilosophy.Thisbookevaluatesthe
principleanddiscussesitsmanyapplications.Fascinatingexamplesfrom
differentdomainsprovidearichbasisforcontemplatingtheprinciple’s
promisesandperils.Itisobviousthatsimplertheoriesarebeautifulandeasy
tounderstand;thehardproblemistofigureoutwhythesimplicityofa
theoryshouldberelevanttosayingwhattheworldislike.Inthisbook,the
ABCsofprobabilitytheoryaresuccinctlydevelopedandputtoworkto
describetwo“parsimonyparadigms”withinwhichthisproblemcanbe
solved.
elliott sober isHansReichenbachProfessorandWilliamF.Vilas
ResearchProfessorintheDepartmentofPhilosophy,Universityof
Wisconsin,Madison.In2014thePhilosophyofScienceAssociationawarded
himtheCarlGustavHempelAwardforlifetimeachievementinphilosophy
ofscience.HispublicationsincludeEvidenceandEvolution:TheLogicBehindthe
Science(2008),DidDarwinWritetheOriginBackwards?:PhilosophicalEssayson
Darwin’sTheory(2011),andUntoOthers:TheEvolutionandPsychologyofUnselfish
Behavior(1998,coauthoredwithDavidWilson).

Ockham’s Razors
A User’s Manual
ELLIOTT SOBER
UniversityPrintingHouse,CambridgeCB28BS,UnitedKingdom
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Firstpublished2015
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Sober,Elliott.
Ockham’srazors:auser’smanual/ElliottSoberforEzraWilliamDidier-Sober.
pages cm
Includesbibliographicalreferencesandindex.
ISBN978-1-107-06849-0(hardbackpaper) 1.Reasoning. 2.Problemsolving.
3.Simplicity(Philosophy) 4.William,ofOckham,approximately1285–approximately
1349. 5.Philosophy,Medieval. I.Title.
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Contents
Acknowledgments pagex
Introduction 1
1 Ahistoryofparsimonyinthinslices
(fromAristotletoMorgan) 4
Thenamingceremony 4
Aristotle’sprinciplethatnaturedoesnothinginvain 6
HowOckhamwieldshisrazor 9
Geocentricandheliocentricastronomy 12
DescartesandLeibnizonGodandthelawsofnature 22
Descartes’sderivations 24
Leibnizonthebestofallpossibleworlds 26
Newtononavoidingtheluxuryofsuperfluouscauses 33
Humeontheprincipleoftheuniformityofnature 37
Kant’sdemotionofGod 40
Whewell’sconsilienceofinductions 44
Milltriestocuttherazordowntosize 49
JamesClerkMaxwell,theevangelicalphysicist 50
Morgan’scanon 51
Concludingcomments 58
2 Theprobabilisticturn 61
Twophilosophiesofprobability 61
AprobabilityprimerandthebasicsofBayesianism 64
Ockham’srazorforBayesians 84
Twokindsofpriorprobability 85
Jeffreys’ssimplicitypostulate 87
Popper’sobjectiontoJeffreys’spostulate 91
vii
viii Contents
Popper,falsifiability,andcorroboration 93
Popper’scharacterizationofsimplicity 97
Parsimonyandnon-firstpriors 99
Likelihoodsandcommoncauses 102
Onsimilarity 119
Athree-wayReichenbachiandistinction 120
BayesianOckham’srazor 123
Frequentismandadjustableparameters 128
Howmanycausesforasingleeffect? 135
Bayesianmodelselection 138
Theworldofmodelselection 140
Howthetwoparsimonyparadigmsdiffer 141
Whyafalsemodelcanbemorepredictivelyaccurate(andcloserto
thetruth)thanatrueone 145
Whatthetwoparsimonyparadigmshaveincommon 147
Concludingcomments 148
3 Parsimonyinevolutionarybiology–phylogeneticinference 153
Commonancestry 154
Somehistory 162
OckhammeetsMarkov 169
Twomodelsthatentailmirroring 176
Symplesiomorphies 178
TheSmith/Quackdoodletheorem 180
Estimatingcharacterstatesofancestors–twoexamplesinwhich
mirroringfails 181
Anothercriterion–statisticalconsistency 184
Stillanothercriterion–whenisparsimonymorereliablethan
guessing? 188
Forwardsandbackwards 189
Estimatingthecharacterstateofaleaf–anthropomorphismand
comparativepsychology 190
Parsimonyoldandnew 197
Concludingcomments 197
Appendices 200
4 Parsimonyinpsychology–chimpanzeemind-reading 207
Experiments 209
Conflictinginterpretations 212
Contents ix
Whiten’sarrows 215
Thetwoparsimonyparadigms 217
Lessonsfromtheblackbox 221
Adifferentmind-readingmodelthatalsoentailsnoscreening-off 226
Learningandscreening-off 227
Associations,correlations,andtesting 229
Parsimonyredux 231
Across-chimpanzeecomparisonthatisnotaboutscreening-off 232
Behaviorismversusmentalism 234
Concludingcomments 239
5 Parsimonyinphilosophy 244
Naturalisms 244
Atheismandtheproblemofevil 246
Absenceofevidenceandevidenceofabsence 252
Themind/bodyproblem 253
Thecausalefficacyofthemental 260
Moralrealism 264
Misinterpretingscreening-off 268
NominalismandPlatonismaboutmathematics 272
Solipsism 276
Theproblemofinduction 283
Concludingcomments 286
References 291
Index 309