牛津大學哲學概論PeterMillicanGeneraPhilosophyGeneralMT116PerceptionPQSQ

GeneralPhilosophyDrPeterMillican,HertfordCollegeLecture6:PerceptionandthePrimary/SecondaryQualitydistinction2TheMechanismsofPerceptionThe“mechanicalphilosophy”ofDescartesandothershadtoexplainperceptionintermsofparticles(orwaves)affectedbytheobjectsandinturnimpactingonoursenseorgans.Mostdiscussionfocusedonsightandtouch,thetwosensesthatseemtocomeclosesttopresentingexternalobjectsasawhole.Locke’saccountwasparticularlyinfluential,emphasisingtheprimary/secondarydistinctionwhichhadbeenimplicitinDescartes.3WhatareObjectsLike?Mechanicalexplanationsofperceptionimplythatourimpressionsofobjectsareconveyedbymechanismswhosestages(e.g.impactofparticlesonoursenseorgans)bearnoresemblancetotheobjectsthemselves.Themechanicalparadigmalsosuggeststhatobjects’fundamentalpropertieswillbethoseinvolvedinmechanicalinteraction–i.e.geometricalanddynamicproperties.4LockeandCorpuscularianismLocketakesBoyle’s“corpuscularianhypothesis”(IViii16)asplausible:Propertiesofsubstancesarisefromtheir

particularmicro-structure:composedof

“corpuscles”of“universalmatter”(Boyle)

or“puresubstanceingeneral”(Locke).Underlyingsubstancehasprimaryqualities:

shape,size,movementetc.,texture,and“impenetrability”(Boyle)or“solidity”(Locke).Secondaryqualities(e.g.colour,smell,taste)arepowerstocauseideasinus.5Pains,Colours,andShapesSupposeacircularhotplateonanovenisglowingredhot.Ibringmyhandclosetoitandfeelwarmth,thenpain…Thesensationsoffeltwarmthandpainareclearly“inthemind”.Thecircularshapeofthehotplateis,weareinclinedtosay,“reallyintheobject”.Soistheredcolourofthehotplate“inthemind”or“intheobject”?6AProblematicTextLocke’sEssay,IIviii10: “SuchQualities,whichintrutharenothingintheObjectsthemselves,butPowerstoproducevariousSensationsinusbytheirprimaryQualities,i.e.bytheBulk,Figure,Texture,andMotionoftheirinsensibleparts,asColours,Sounds,Tasts,etc.TheseIcallsecondaryQualities.Thecommabefore“but”isunfortunate.Lockemeans“nothing…butpowers”.7InObjects,orJustIntheMind?LockeseesbothPQsandSQsasgenuinepropertiesofobjects,buttheSQsarenothingbutpowersduetotheirPQs.BerkeleyreadLockeassayingthatSQsareonly“inthemind”andnotreallypropertiesofobjects.ButLockeisclearthatoursimpleperceptionsofobjects’colouretc.are“adequate”:theyfaithfullyrepresenttheir“archetypes”(IIxxxi1,12): “SimpleIdeas…are…certainlyadequate.BecausebeingintendedtoexpressnothingbutthepowerinThingstoproduceintheMindsuchaSensation…”8WhyResemblance?HenceLocke’semphasisonresemblance,ratherthanrealexistenceinobjects,asthekeydistinctionbetweenPQsandSQs: “theIdeasofprimaryQualitiesofBodies,areResemblancesofthem,andtheirPatternsdoreallyexistintheBodiesthemselves;buttheIdeas,producedinusbytheseSecondaryQualities,havenoresemblanceofthematall.ThereisnothinglikeourIdeas,existingintheBodiesthemselves.”(EssayIIviii15)9CananIdeaResembleanObject?Berkeley(PrinciplesI8)isemphaticthat: “anideacanbelikenothingbutanidea;acolourorfigurecanbelikenothingbutanothercolourorfigure.”HisattackonLocke’sresemblancethesisseemstobebasedontheprinciplethatideasareintrinsically“perceivable”.ThisisveryplausibleforSQs–nothingcanbelikeasensedsmell,orcolour,unlessitismental(aswithafeltpain).10StructuralResemblance?ButideasofPQsseemtolackthisintimateconnexionwithmentality–theyaremoreabstractandstructural,asillustratedbytheiruseingeometricalmechanics.Wecanusethese“mathematical”propertiestocalculatepredictionsaboutobjects’behaviour,andfindthatthese“work”.Soit’splausiblethatideasofPQscanresemblenon-mentalrealityinastructuralway(cf.LoweonLocke,pp.57,63-4).11SolidityHoweversolidityseemstobeanoddmanout–ourideaofsolidityseemsclearlytobetheideaofapower(orrather,perhaps,theunknowngroundofapower),andwithoutanyresemblancetoapropertyofobjects.Solidityisapower–oradisposition–toexcludeotherbodies.Butwhatisabody?Bodyisdistinguishedfromemptyspacebyitssolidity,sothewholethingiscircular!12Hume’sCriticism(TreatiseIiv4) “Twonon-entitiescannotexcludeeachotherfromtheirplaces…NowIask,whatideadoweformofthesebodiesorobjects,towhichwesupposesoliditytobelong?Tosay,thatweconceivethemmerelyassolid,istorunonininfinitum.…Extensionmustnecessarilybeconsider’deitherascolour’d,whichisafalseidea[becauseit’saSQ,supposednottobe“in”objects];orassolid,whichbringsusbacktothefirstquestion.…[Hence]aftertheexclusionofcolours(etc.)fromtherankofexternalexistences,thereremainsnothing,whichcanaffordusajustandconsistentideaofbody.”13EmpiricismandUnderstandingTheattackonresemblancethusleadsnaturallytoanattackbasedonourlackofunderstandingofthequalitiesconcerned.Ifallourideasarederivedfromexperience(asLockehadinsisted),thenourideasofPQs(e.g.shape)willnaturallybeinfusedwiththoseoftheSQsbywhichweperceivethem(e.g.acolourthatfillsthespace).AndiftheseSQscannotbeunderstoodasexistingoutsideamind…14TheAttackonAbstractionSoBerkeleyandHumeattackLockeonthegroundsthatwecan’tformacoherentideaofmatterwithoutusingideasofSQs.TheyseeLockeasillegitimatelytryingto“abstract”apurelyPQideaofbodyawayfromouractualideawhichisinextricablyboundupwithperceptualnotions.Hencetheirfocusonabstraction(seetheIntroductiontoBerkeley’sPrinciples).15TheCaseforIdealismBerkeleyconcludesfrom

thisargumentthatbodies

independentofmindare

literallyinconceivable.Ifthisworks,itseemsto

showthattheonlywaywe

canmakesenseofthe

worldisasfundamentallyconsistingofmentalentities(i.e.“spirits”and“ideas”.16“SomethingIKnowNotWhat”Todefendrealismweshouldacceptthatourideaofbodyis“inadequate”–wecan’tconceiveofwhatitisthatfillsspaceexceptintermsof“whatitdoes”(cf.EssayIIxxiii2).Moremodernconceptssuchasmassandelectricchargemakethisclearer:weareundernoillusionthatthebasicpropertiesemployedinourscientifictheorieshavetobedirectlyperceivable,orunderstandableinnon-dispositionalterms.17Locke’sIndirectRealism Ideainthemind

(directlyperceived) Materialobject

(causeoftheidea)

The“Veilofperception”problem:howcanweknowwhetherthereisarealmaterialobject?18AnUnacceptableInterpretationIndirectrealismissometimesparodiedastheviewthatinordertoperceiveatree,Imustperceiveanimage-of-a-tree(asthoughsomesortof“homunculus”issittinginmyheadviewingalittleprojectorscreen).Howeverthisclearlydoesn’texplainperception,becauseitpresupposesthattheimage-of-a-treeisitselfperceived.Ifitcanbe“directly”perceived,whycan’tthetree?19SenseDataTwentieth-centuryphilosopherssuchasAyerprefertheterm“sense-data”toLocke’s“idea”,butthisratherlendsitselftotheunacceptableinterpretation.It’sbettertosaythatawarenessofa

“sense-datum”countsasperceptionofanexternalobjectifitwascausedappropriatelybysuchanobject.ButhowcanIknowthatitwassocaused?Againwefacethe“veilofperception”.20HowToProvetheCausalLink? “Itisaquestionoffact,whethertheperceptionsofthesensesbeproducedbyexternalobjects,resemblingthem:Howshallthisquestionbedetermined?Byexperiencesurely…Buthereexperienceis,andmustbeentirelysilent.Themindhasneveranythingpresenttoitbuttheperceptions,andcannotpossiblyreachanyexperienceoftheirconnexionwithobjects.Thesuppositionofsuchaconnexionis,therefore,withoutanyfoundationinreasoning.”(Hume,Enquiry12.12)21PhenomenalismPhenomenalismistheviewthatphysicalobjectsarelogicalconstructionsoutofsense-data.Sostatementsaboutsuchobjectsareinterpretedasstatingwhatwouldbeperceivedincertaincircumstances.ThisaimstoevadetheBerkeleianargumentthatonecannotmakesenseofphysicalobjectsinabstractionfromperceptions;ItalsoaimstoanswertheHumeanargumentoftheveilofperception.22DirectRealismRatherthanresorttophenomenalism,amorepopularrecentview(sinceJ.L.AustinandP.F.Strawson)hasbeentoinsistthatweperceiveobjectsdirectly.Thisseemsright,insofarasitisintendedtocountertheUnacceptableInterpretation.Howeveritdoesn’tsolvethescepticalproblems,andcanseemmerelyverbal:itisacceptedthatourperceptionismediated

physically(bylightraysetc.);thepointisjustthatwedoperceiveobjects(andseethemasobjects)bythatmeans.