PHILOSOPHYOFLANGUAGE语言哲学

PHILOSOPHYOFLANGUAGE语言哲学

PHILOSOPHYOFLANGUAGEHOWTOTALKABOUTTALK\nLOGICALSEMANTICSRemember:Inlogicalgrammarthereare5kindsofexpressions:Predicates:woman,sweet,walksNames:Fred,∞,ColoradoDefinitedescriptions:thesquarerootof4,theKingofFrance,themandrinkingamartiniLogicaloperators:and,or,not,if,then,any,each,some,most,atleastone.Thefirstfourarecalled“sententialconnectives,”theremainingonesarecalled“quantifiers.”Sentences\nLOGICALSEMANTICSPredicatesstandforclassesofthings.So,applestandsfortheclassofapples.NoteWell:WhenIaskedtheclasswhatapplestoodforsomepeoplesaid“afruit.”ButIwasn’taskingforanexplanationofwhatapplesare.Iwasn’taskingforadictionarydefinition.Iwasaskingwhatthingsyouwouldpointtowhenteachingachildtousethewordapple.Thatwouldbeapples,ofcourse.Comprende?Namesstandfororrefertothesinglethingstheyarenamesof.\nLOGICALSEMANTICSDefinitedescriptionsalsoreferorstandforsingleobjects.TheFstandsfortheuniquethingthatisF,ifthereisone.Ifthereisn’tone,thedefinitedescriptionisimproper.ExamplesQuestions:IstheRockyMountainsanameoradefinitedescription?Ismyfatheradefinitedescription?Sentencesstandfortruthvalues.Soalltruesentencesstandforthesamething,namely,thetruth.Likewiseforallfalsesentences.Sohereagainweseethedifferencebetweenmeaningandreference.Notalltruesentenceshavethesamemeaning!Otherwisetherewouldbeonlyonetruestatementtomake!\nSenseandReferenceWehaveseenthattherearepairsofexpressionsthat(a)havethesamereference(nominatum),but(b)donothavethesamesenseormeaning.MoreexamplesItwasFregewhofirstcalledattentiontothisratherobviousfact.Butifit’ssoobvious,what’sthebigdeal?Thebigdealisthatsuchexamplesconfirmthatmeaning(sense)andreferencearenotthesamething.Ingeneral,themeaningofawordorphraseorsentenceisnotthethingorthingstheword(etc.)standsfor.\nSENSEANDREFERENCEEventhoughwesaywewouldteachachildthe“meaning”ofthewordwaspbypointingoutthereferents--thethingsbelongingtotheclassofwasps(wasps)andsaying“wasp,”wedonottherebyconveythemeaningoftheword!AtleastthatiswhatFregeiscommittedtosaying.ForFrege,themeaningofanyexpression(logicaloperatorsaside)isonething,itssenseisanother.YoushouldthinkaboutthispointcarefullybecauselaterwewillfindthatKripkearguesthatFregeiswrongaboutwordslikewasp,thoughheisrightaboutotherexpressions.(Butwhatcouldbesospecialaboutwasp?)ItwasFregewhofirstcalledattentiontotheimportanceofthesense/referencedistinction.\nFrege’sArgumentFregedidn’tsimplypointoutthattherearepairsofexpressionshavingthesamereferencebutthatdifferinsense,andhencethatsenseandreferencearenotthesamething.Hegaveaspecial,rathercomplicatedargument--onethatwouldonlyoccurtoaphilosopher/logician.ButFrege’sargumentismeanttosupportthepositionthateverytypeofexpressionexhibitsthesense/referencedistinction.Thesimplerargumentwon’tsupportthatposition.We’llseewhylater.\nFREGE’SARGUMENT“Whenwefound‘a=a’and‘a=b’tohavedifferentcognitivevaluestheexplanationisthatforthepurposeofknowledge,thesenseofthesentenceisnolessrelevantthanitsreference,itstruthvalue.Ifnowa=b,thenindeedthereferenceof‘b’isthesameasthatof‘a’.\nFREGE’SARGUMENTCONTINUEDAndhencethetruthvalueof‘a=b’isthesameasthatof‘a=a’.Inspiteofthisthesenseof‘b’maydifferfromthatof‘a’,andtherebythethoughtexpressedin‘a=b’differsfromthatof‘a=a’.Inthatcase,thetwosentencesdonothavethesamecognitivevalue.”\nFREGE’SDIALECTICWecouldtryputtingallthisinargumentform.Weuncovertheconclusionandthepremises(reasonssupportingtheconclusion)andthenweevaluatetheargumenttoseeifitisanygood.ButIthinkthiswouldmissmuchoftheaction.ItwillbemorefuntofocusonFrege’sdialectic:theparticularwayhesetsuptheproblemanddealswithit.Fregefocusesfirstonidentitystatements.Why?\nFREGE’SDIALECTICExamples:Creatureswithaheartare(=)creatureswithakidney.Jonesis(=)themurderer.thesuntodayisthesameas(=)thesunyesterday.Question:Whydoeshefocusonsuchstatements?Answer:Hewantstofocusonexpressionshavingthesamereference.(Why?)Andtwoexpressionsaandbhavethesamereferencejustincasea=bistrue!\nFREGE’SDIALECTICFrege’sdialecticproceedsasfollows:Hefirststatesafact:Identitystatementsoftheforma=bcandifferin“cognitivevalue”fromtrivialstatementsoftheforma=a.Fregethenarguesthatthisfactis,onthefaceofit,contrarytologic.Heconcludesthatfactandlogiccanbereconciledbymeansofthesense/referencedistinction.\nDETAILSAbout1:BycognitivevalueFregejustmeansthevalueoftheinformationconveyed.IfIinformthepolicethatJonesisthemurder,Igivetheminformationtheycanacton.ButifItellthemthatthemurderisthemurderer,theywouldjustlaugh.About2:Butifallidentitystatementsstatetheobvious--thatanobjectisidenticaltoitself,thenhowcananyofthemconveyusefulinformation?\nDETAILSMoreabout2:Butit’sobviousthatnotallidentitystatementsstatetheobvious,sincesomearefalse.Moreabout2:However,ifitistruethatJonesisthemurderer,andthereisnosuchthingasthesense/referencedistinction,thenhowcanJonesisthemurderersayanythingmorethanthatthemurdereristhemurdererorJonesisJones?Itcan’t.About3:Therefore,weneedthesense/referencedistinctiontoexplainhowa=b,iftrue,candifferincognitivevaluefroma=a(orb=b).Theexplanationisthatifaandbdifferinsense,ifnotinreference,thena=bcanconveyusefulinformation.\nOTHERSUPPORTFORTHEDOCTRINEOFSENSESSomemeaningfulexpressionshavenoreference.Predicatesalwaysrefer,sinceevenifthepredicateappliestonothing,itsreferencewillstillbeaset--namely,theemptyset.Butotherexpressionsseemtolackreferencealtogether.Examples:thelargestnumber,thepresentKingofFrance,SherlockHolmesFregecan(anddoes)appealtothedoctrineofsensetoexplainhowtheseexpressionscanbeusedmeaningfullyeventhoughtheylackreference.\nOTHERSUPPORTFORTHEDOCTRINEOFSENSES2.Fregearguesthatthereferencesofsentencesaretheirtruthvalues.Whetherthisissoornot,thedoctrineofsensesisneededtoexplainwhyitisnottruethatalltrue(orfalse)sentenceshavethesamemeaning.3.Fregecananddoesusethesense/referencedistinctiontosolvethefollowingirritatingbutdeeper-than-you-thinkpuzzle:\nOTHERSUPPORTFORTHEDOCTRINEOFSENSEA:TheBabyloniansbelievedthatthemorningstaristhemorningstar,istrue.ButthesentenceB:TheBabyloniansbelievedthatthemorningstaristheeveningstar,isfalse.Yetsincethemorningstaristheeveningstar,logic,unsupplementedbythesense/referencedistinction,dictatesthatifAistrue,asitis,thenBshouldalsobetrue.Why?FregearguesthatitispreciselythefactthatthemorningstarandtheeveningstardifferinsensethataccountsforthedifferenceintruthvalueofAandB.\nWHATARESENSES?Twokindsof“whatare(is)soandso”questions.TothefirstFregewouldanswerthatsensesare“modesofpresentation”(ofthereferences).Thetriangleexample.Thepointofintersectionoflinesaandb=thepointoflinesbandc.SomecriticshavepointedoutthatthereissometensionbetweenthisexplanationandFrege’sviewofemptyterms.\nWHATARESENSES?Tothesecondtypeof“whatis”questionFregeanswersasfollows:“Thereferenceofapropername[orotherreferringexpression]istheobjectitselfwhichwedesignatebyitsmeans;theideaiswhollysubjective;inbetweenliesthesense,whichisindeednolongersubjectiveliketheideabutisyetnottheobjectitself.”And“theideaarousedinahearerbyawordshallnotbeconfusedwithitssenseorreference.”Thetelescopeexample\nTHEREFERENCEOFSENTENCESTheSlingshot(Church’sVersion)Frege’sPrinciple:Substitutionofco-referringexpressionspreservesthereferenceofthewholecompoundexpression.Example:thecenterofmassoftheearthisthecenterofmassofthethirdplanetfromthesun.Fregeextendsthisprincipletocompoundsthataredeclarativesentences.Step1.SirWalterScottistheauthorofWaverly.Step2.SirWalterScottisthemanwhowrote29Waverlynovels.[ByFrege’sPrinciple.]Step3.ThenumberofWaverlynovelsSirWalterScottwroteis29.[ExpressesthesamepropositionasinStep2.]Step4.ThenumberofcountiesinUtahis29.[ByFrege’sPrinciple.]\nTHREEPROBLEMSWhatisthesenseofanactualpropername?Frege’swrites:“InthecaseofanactualpropernamesuchasAristotleopinionsastothesensemaydiffer.”Possibility:thepupilofPlatoandteacherofAlexandertheGreat.ButthenifAristotlehadn’tdonethesethingshewouldnothavebeenAristotle;andifsomeoneelsehaddonetheminstead,hewouldhavebeenAristotle!Thatseemscompletelywrong.AristotlewasAristotlewhetherornothedidthesethings.ThisisoneofthecriticismsKripkedevelops.\nTHREEPROBLEMS2.Incontrastingthecognitivevalueofa=awiththatofa=b,Fregeclaimsthattheformeris“analytic”and“apriori.”Thisjustmeansthata=aisguaranteedtobetruebypureelementarylogicalone,andthatitcanbeknowntobetruewithoutanyexaminationoftheworld(providedweassumeaisnotempty).ThissuggeststhatFregethoughtthata=b,iftrueandinformative,isneverguaranteedtobetruebylogicaloneandthatitisneverapriori.Butwhataboutmathematicalidentitiessuchas2isthepositivesquarerootof4.Can’tweseethisapriori?Butit’sstillinformative.Andisn’titguaranteedtobetrue,ifnotbylogic,thenbymathematics?\nTHREEPROBLEMS3.ConsiderascientificidentitystatementsuchaswaterisH2O.WhatisFregecommittedtosayingaboutthis?(a)It’sinformative;(b)it’snotanalyticorapriori;(c)thewordswaterandH2Odifferinsense.Judgingfromwhathesaysaboutpropernames,Fregewouldprobablyholdthatthesenseofwaterissomethinglike“theclearliquidfoundinoceans,lakes,etcand….Wherethismaybefleshedoutbydescriptionsofthestereotypicalpropertiesofwater.OnthisreadingthestatementthatwaterisH2Omighthaveturnedouttobefalse.How?ButKripkearguesveryeffectivelythatifthestuffinourriversandstreamsetc.hadbeensomethingotherthanH2O,itwouldnothavebeenwateratall.Ifso,whatfollowsasregardsFrege’sposition?