Empiricism and Philosophy of Physics PDF
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Synthese Library 434 Studies in Epistemology, Logic, Methodology, and Philosophy of Science Lars-Göran Johansson Empiricism and Philosophy of Physics Synthese Library Studies in Epistemology, Logic, Methodology, and Philosophy of Science Volume 434 Editor-in-Chief OtávioBueno,DepartmentofPhilosophy,UniversityofMiami,USA Editors BeritBrogaard,UniversityofMiami,USA AnjanChakravartty,UniversityofNotreDame,USA StevenFrench,UniversityofLeeds,UK CatarinaDutilhNovaes,VUAmsterdam,TheNetherlands DarrellP.Rowbottom,LingnanUniversity,HongKong EmmaRuttkamp,UniversityofSouthAfrica,SouthAfrica KristieMiller,UniversityofSydney,Australia TheaimofSyntheseLibraryistoprovideaforumforthebestcurrentworkinthe methodology and philosophy of science and in epistemology. A wide variety of different approaches have traditionally been represented in the Library, and every effortismadetomaintainthisvariety,notforitsownsake,butbecausewebelieve thattherearemanyfruitfulandilluminatingapproachestothephilosophyofscience andrelateddisciplines. Specialattentionispaidtomethodologicalstudieswhichillustratetheinterplay of empirical and philosophical viewpoints and to contributions to the formal (logical,set-theoretical,mathematical,information-theoretical,decision-theoretical, etc.) methodology of empirical sciences. Likewise, the applications of logical methodstoepistemologyaswellasphilosophicallyandmethodologicallyrelevant studiesinlogicarestronglyencouraged.Theemphasisonlogicwillbetemperedby interestinthepsychological,historical,andsociologicalaspectsofscience. BesidesmonographsSyntheseLibrarypublishesthematicallyunifiedanthologies andeditedvolumeswithawell-definedtopicalfocusinsidetheaimandscopeofthe book series. The contributions in the volumes are expected to be focused and structurally organized in accordance with the central theme(s), and should be tied togetherbyanextensiveeditorialintroductionorsetofintroductionsifthevolume isdividedintoparts.Anextensivebibliographyandindexaremandatory. Moreinformationaboutthisseriesathttp://www.springer.com/series/6607 ¨ Lars-Goran Johansson Empiricism and Philosophy of Physics Lars-Go¨ranJohansson DepartmentofPhilosophy UppsalaUniversity Uppsala,Sweden ISSN0166-6991 ISSN2542-8292 (electronic) SyntheseLibrary ISBN978-3-030-64952-4 ISBN978-3-030-64953-1 (eBook) https://doi.org/10.1007/978-3-030-64953-1 ©TheEditor(s)(ifapplicable)andTheAuthor(s),underexclusivelicensetoSpringerNatureSwitzerland AG2021 Thisworkissubjecttocopyright.AllrightsaresolelyandexclusivelylicensedbythePublisher,whether thewholeorpartofthematerialisconcerned,specificallytherightsoftranslation,reprinting,reuse ofillustrations,recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,and transmissionorinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilar ordissimilarmethodologynowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthors,andtheeditorsaresafetoassumethattheadviceandinformationinthisbook arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor theeditorsgiveawarranty,expressedorimplied,withrespecttothematerialcontainedhereinorforany errorsoromissionsthatmayhavebeenmade.Thepublisherremainsneutralwithregardtojurisdictional claimsinpublishedmapsandinstitutionalaffiliations. ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland Preface Praeteracenseometaphysicamessedelendam. (Furthermore,Iconsiderthatmetaphysicsmustbedestroyed.) AxelHägerström Entianonsuntmultiplicandapraeternecessitatem (Entitiesshouldnotunnecessarilybemultiplied.) WilliamofOckham Thepurposeofthisbookistwofold:(i)topresentathoroughlyempiricistposition inepistemologyand(ii)toapplyittophilosophyofphysics.Mymotiveisthesame asthatofthelogicalempiricists,viz.,(i)totellwhattocountasempiricalevidence foratheoryand(ii)topresentaphilosophicalviewonscience,inparticularphysics, whichdoesnotengageinanysuperfluousmetaphysics. Empiricists are united in holding that empirical evidence is the only evidence therecouldbeforanempiricaltheory;thecrucialquestionistosaymoreprecisely whattocountasempiricalevidence.Regardingmetaphysics,thecrucialquestionis howtodistinguishbetweensuperfluousandnon-superfluousmetaphysics. Adherents to logical positivism were hostile to theoretical entities. A common viewwastodistinguishbetweenobservableandnon-observable,thatis,theoretical entities, where the latter were viewed with scepticism. Modern empiricists, for example van Fraassen, hold in a somewhat similar vein that we have no good reason to believe theoretical sentences being true. (But he accepts that theoretical sentences are truth-apt.) Scientific realists by contrast believe in the existence of sometheoreticalentitiesandthatwehavegoodreasontothinkatleastsometheories are approximately true. In my view, neither the scientific realist’s defence of their views nor the empiricist’s criticism are well founded. In this book, I will develop what I hope is a more tenable version of empiricism, not based on the distinction betweenobservable/non-observable,butinsteadbasedonsemanticconsiderations. v vi Preface A fundamental distinction in semantics is between singular and general terms, the latter alternatively called predicates.1 The referent of a singular term, if it exists, is an individual, whereas the referent of a general term, if it exists, is a universal.(ThiswillbethoroughlydiscussedinChap.3.)Whenweacceptatheory as (approximately) true, we tentatively accept all its sentences as being true. It follows that its singular terms must refer to things that exist and the domains of its first-order variables must be non-empty. But it does not follow that the general termsdeployedmusthavereferents,northatsecond-orderquantificationisneeded. Myontologicalpositionisthatweneverhavegoodreasonforassumingproperties andrelations,thatis,universals,asreferentsofgeneralterms;theyaresuperfluous. IthusadheretonominalismintheveinofOckhamandGoodman,tobediscussed inChap.3. The question of ontology is intimately connected to semantics. The question ‘Whatexists?’maybeviewedasshortfor‘Whatexistsaccordingtoourbesttheory oftheworld?’andtheansweris:Whenweholdatheorytobetrue,orapproximately so, we must accept as existing those things which the theory says exist. But an empirical theory is rarely explicit about the ontological commitments made when acceptingit.Weneedtoparaphrasephysicaltheoriesintopredicatelogicinorderto seetheirexistenceassumptions. The fundamental issue in the semantics of scientific theories is the connec- tion between theory and reality. When contemplating this issue, I have found Löwenheim-Skolem’s theorem of utmost importance. This theorem says, roughly, thatnotheorybyitselfcandeterminewhatitisabout.FromLöwenheim-Skolem’s theorem it follows that the connection between theory and reality must be estab- lishedbynon-theoreticalmeans.2 Theseconsistofindexicalwords,suchas‘this’, ‘that’,‘here’and‘now’,usedinconnectionwithpointinggestures;suchcombina- tionsofindexicalexpressionsandgesturesdeterminethereferencesofcertainterms. Forexample,thereferenceofthesingularterm‘thisdetector’usedinthesentence ‘Thisdetectornowshows50counts’isdeterminedastheveryobjectpointedatin aparticularsituationwhereatokenofthissentenceisused.Löwenheim-Skolem’s theoremtellsusthatsuchconcreteusesareneededforconnectingatheorytoreality. Thisfitsnicelyintoanempiricistoutlook. This book is thus based on three foundations: empiricism in epistemology, nominalisminontologyandLöwenheim-Skolem’stheoreminsemantics.Thiswill beelaboratedinsomedetailinChap.3. A great part of philosophy of science is philosophy of physics. This is easy to understand: since physics is the most basic and general of all empirical sciences, 1Onemayholdthatgeneraltermsandpredicatesarestrictlyspeakingnotthesamekindsofthings, butforthisdiscussionthedifferencedoesn’tmatter. 2Ifweuseanauxiliarytheoryforrelatingaparticulartheorytoreality,wecanviewthisauxiliary theoryasanextensionoftheoriginaltheoryandLöwenheim-Skolem’stheoremappliesalsotothis extendedtheory. Preface vii philosophical discussions concerning fundamental issues in philosophy of physics implicitlycoveralsosomefundamentalissuesinallsciences. Alargeproportionofphilosophyofscience,inparticularphilosophyofphysics, isdevotedtologicalandformalaspectsoftheories,suchastheirformalsemantics and axiomatisation. For certain purposes this is interesting, but I will not discuss such matters. My focus of interest in this book is epistemological and ontological questions, both in relation to physics. Therefore, I see no need to say anything about formal semantics, axiomatisation, consistency or set theoretical foundations of science. With only little exaggeration, one may say that these topics are about relationsbetweenwordsonly;theyrarelyhavemuchbearingonhowwordsrelate totheworld.NordoIneedmodallogic,whichmayastonishmostreaders,forhow could one give an account of natural laws without talking about their necessity? Well,Icertainlyaccept thatlaws,properlysocalled,arenecessaryinsomesense, butIneednomodallogicformyaccountoftheirnecessity,aswillbeexplainedin Chap.10. The first two chapters give a background for the rest of the book. Chapter 1 listsanumberofphilosophicalproblemsinphysics,whichareinterestingfroman empiricist point of view, and Chap.2 presents very briefly the development from Aristotle’sphysicstoquantumtheory.Itisnotreallyanythingthatcanbecalleda historyofphysics;itcontainsonlysomeaspectswhicharerelevantfortheensuing chaptersonissuesinphilosophyofphysicswhichIhavefoundinteresting. Chapter3isanoverviewoftheempiricisttraditionanditendswithwhatIbelieve is a tenable version of empiricism. Chapter 4, about mathematics, may seem a bit odd in this context, but I have come to the conclusion that it should be included: physics and mathematics are so intimately related that it is almost impossible to avoidtakingastanceonquestionsaboutmathematicalknowledgeandmathematical objectswhendiscussingontologyandsemanticsofphysicaltheories.Inparticular, Ihavearrivedattheconclusionthatevenforanempiricist,thereisgoodreasonto acceptmathematicalobjects,forexample,vectors,intheontology.Butwehaveno goodreasontoassumethattherearephysicalentities,suchasforces,corresponding to vectors in the mathematical sense. And similar reflections apply to spacetime: Just because a Lorenzian manifold with a metric, a mathematical entity, is very usefulinrelativitytheory,itdoesnotfollowthatthatthismathematicalobjecthas acounterpartinthephysicalworld.Wecandowithoutassumingaphysicalentity spacetime. Chapters5to8discuss topics ingeneral philosophy ofscience and Chaps.9to 17narrowdowntosomespecificissuesinphilosophyofphysics. Great parts of Chap.5 is taken from my ‘Induction and Epistemological Natu- ralism’,Philosophies,3,31,2018.Chapters10,11and12arepreviouslypublished papers,whichherearereprintedwithminorchanges(suchasreplacing‘thispaper’ with‘thischapter’)asadaptionstothecontextofabook.Chapter10waspublished as‘TheOntologyofElectromagnetism’,StudiaPhilosophicaEstonica,10(1)2017, 25–44, Chap.11 was published as ‘An Empiricist View on Laws, Quantities and PhysicalNecessity’,Theoria85,2,69–101,April2019,andChap.12waspublished as‘Propensities’,pp.161–175inLogic,EthicsandallthatJazz.Essaysinhonourof viii Preface JordanHowardSobel,editedbyLars-GöranJohansson,JanÖsterbergandRysiek Sliwinski.Uppsala:DepartmentofPhilosophy,UppsalaUniversity.2009,Uppsala Philosophical Studies 57. For the papers on electromagnetism, epistemology and propensities, I have the copyright, whereas Theoria foundation has the copyright forthepaperonlaws.IherebythankTheoriaforpermissiontoreprintithere. Anoteontheterms‘concept’and‘predicate’ The word ‘concept’ is one of the most common words in philosophy, but, alas, it is often not very clear what it is supposed to refer to. In this book, I will use it asmeaning‘generaltermadjoinedwithrulesforitsapplication’.Inphysics,these rulesaresometimesexplicitlystated,asisthecasewithquantitiesandunitsdefined in the SI system. Thus, a concept, in my use of that word, is basically a linguistic item,notsomethinginourminds. Use-mentionconfusionisstillcommon,inspiteofQuine’slongfightagainstit. In order to be absolutely clear about the distinction between talking about a term andusingit,Iwillusethetextstyle SMALL CAPITAL whenItalkabout ageneral term(=concept).Thus,observethecontrastbetween‘TIMEisthefourthcoordinate infour-dimensionalspacetime’and‘Theemissiontimeisfourseconds’.Similarly, ‘The charge of an electron is −1.6 ∗ 10−19 Coulomb’ whereas ‘CHARGE is an electromagneticquantity’.However,whenIquotesomeoneelse,Ikeeptheoriginal text style; so, for example, Weyl uses boldface when he talks about concepts, see thequoteinChap.9. Concepts,typesandtokens A token of a term is a physical object, whereas a term in the sense of type is an abstractobject.Itistemptingtosaythatatypeisthesetofallitstokens.Butthat isproblematic,forwewouldnotacceptthatanewoccurrenceofatokenofaterm, whichobviouslychangestheset,entailsthatthetypehaschanged;hence,typesof termscannotbegivenanextensionalreading.So,wemustacceptthattermsinthe sense of types must be taken as primitive abstract objects, not reducible to sets of concreteobjects. The introduction of abstract objects into discourse is a manifestation of our general capacity for generalising. We begin teaching our children words for observable things such as dogs, balls, apples, dolls, etc. When a child masters the word ‘dog’, she/he usually recognises a new object as being a dog, if it is a dog, and may say ‘dog’. The inductive generalisation works on both sides, so to say: a new object is cognised as sufficiently similar to a set of earlier observed objects, andthetokensoftheword‘dog’heardinassociationwithobservationsofdogsare cognisedassufficientlysimilartoeachother,andsomethingapproximatelysimilar isproducedwhenseeingthedog.So,bothcognitionandlanguageuseisbasedon ourcapacityforgeneralisation. Thus, even at the most basic level of thinking and language use, we deploy abstract objects, that is, word types. Since I will argue for nominalism in the vein of Ockham and Goodman, it might seem inconsistent to accept abstract objects in the universe of discourse. But it is not. The distinction concrete-abstract is not Preface ix the same as the distinction individual-universal. I adopt Aristotle’s notion of an individualobject,whichAristotlecalledaprimarysubstance,asthatwhichonlycan bethesubjectofaproposition,neverbeingapredicate,albeitrephrasedinmodern semantic terms: an individual object is the referent of a singular term, never of a general term.And there are lots of abstract objects thatare referred to by singular terms,mostobviouslynumbers,whichwerefertoby,forexample,numerals.That a natural number may be viewed as constructed as a set of sets is no objection. The European Commission consists of 27 persons. Still it is an individual, since ‘TheEuropeanCommission’isasingularterm.SomynominalismisGoodman’s; Iresolutelyrejectuniversalsasreferentsofgeneralterms.So,forexample,thetwo- placepredicate‘∈’hasextensionbutnoreferent,asallgeneralterms. UpplandsVäsby Lars-GöranJohansson
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