Explanatory Pluralism And The Co-Evolution Of Theories In Science …mechanism.ucsd.edu/~bill/teaching/w17/phil151/mccauley... · 2017-01-12 · Explanatory Pluralism And The Co-Evolution

ExplanatoryPluralismAndTheCo-EvolutionOfTheoriesInScience*

RobertN.McCauley1.IntroductionOverthepastdecadeorsoPatriciaandPaulChurchlandhavemademajorcontributionstophilosophicaltreatmentsofintertheoreticreductioninscience.Thehistoricimportanceofthisissueinthephilosophyofscienceispatentandso,therefore,istheimportanceoftheChurchlands’contributions.Theirinsistenceonthecentralityofthisissuetodiscussionsinthephilosophyofmindmay,however,beevenmorepraiseworthyinanerawhenmanyinthatfield(evenamongthosewhoclaimthemantleofnaturalism)makerepeateddeclarationsaboutthestatusofthepertinentsciencesandthemind-bodyproblemgenerallyinwhatoftenappearstobeblitheignoranceofboththosesciencesandtherelevantliteratureinthephilosophyofsciencesince1975.Inarecent,jointpapertheChurchlands(1990)discussandlargelydefusefivewell-wornobjections(concerningqualia,intentionality,complexity,freedom,andmultipleinstantiation)tothereductionofpsychologytoneurobiology.MyconcernswiththatputativereductionandwiththeChurchlands’accountoftheoverallprocessareofaverydifferentsort.Twomodelshavetraditionallydominateddiscussionsofintertheoreticrelations.Afterbrieflysurveyingthecontrastsbetweenthem,section2examineshowtheChurchlands’accountoftheserelationsintermsofacontinuumofintertheoreticcommensurabilitycapturesthosemodels’respectiveadvantagesinasingleproposal.ThatsectionendsbyexamininghowPatriciaChurchland’ssubsequentdiscussionsoftheco-evolutionoftheoriesenhancesthisaccountbyexploringsomeofitsunderlyingdynamics.Inshort,theco-evolutionoftheoriesconcernscross-scientificinteractionsthatchangethepositionofaparticularintertheoreticrelationshipontheChurchlands’continuum.Insection3IlocatesomerevealingequivocationsintheChurchlands’discussionsof“theco-evolutionoftheories”bydistinguishingthreepossibleinterpretationsofthatnotionthatwindtheirwaysthroughtheChurchlands’workandthroughNeurophilosophyinparticular.WiththeaidofadistinctionconcerninglevelsofanalysisthatIhavedevelopedelsewhere,Iargue,ineffect,thattheChurchlands’accountoftheco-evolutionoftheoriesandtheirmodelofintertheoreticreductionobscurecriticaldistinctionsbetweenthreequitedifferenttypesofintertheoreticrelations.Section4positionsthesethreetypeswithinamorefine-grainedaccountofintertheoreticrelationsthatwillofferabasisforevaluatingtheirrelativemeritsasanalysesoftheinterfaceofpsychologyandneuroscience.Oneofthesethree,thepictureofco-evolutionmodeledonthedynamicsofscientificrevolutions,hasattractedthemostattention.ThisinterpretationhasencouragedtherecurringeliminativistinclinationsconcerningfolkpsychologyforwhichtheChurchlandsarerenown,but,ofthethree,itisalsotheinterpretationthatisleastplausibleasananalysisoftherelationsbetweenpsychologyandneuroscience.Psychology(folkorotherwise)maywellundergosubstantialrevision,andfuturescientificprogressmaywellleadtotheeliminationofsomepsychologicaltheories,buttheChurchlandshaveofferedanunhelpfullyoversimplifiedaccountoftheintertheoreticdynamicsinquestion.

ExplanatoryPluralismAndTheCo-EvolutionOfTheoriesInScience p,2

Insection5Ishallsupportandelaborateuponanotheroftheinterpretationsofco-evolutionthatemergesfromNeurophilosophyby,amongotherthings,examiningacase(concerningtheconnectionistnetwork,NETtalk)thattheChurchlandsandtheircollaboratorshavehighlighted.Thisthirdinterpretationrecognizesnotmerelythevalueofintegratingscientificdisciplinesbutofpreservingapluralityofsemi-autonomousexplanatoryperspectives.AlthoughtheChurchlandsnowoftenseemtofavorthisthirdinterpretationtoo,someoftheircommentscontinuetoconflatethethreedistincttypesofintertheoreticrelations.2.ThreePhilosophicalModelsofIntertheoreticRelationsinScienceUntilthelate1970s(atleast)twomodelsofintertheoreticrelationsinsciencedominatedphilosophers’attentions.Thefirst,ageneralpurposemodelofintertheoreticrelations,wasdeeplyrootedinlogicalempiricism;thesecond,ineffectamodeloftheorychange,emergedlargelyinreactiontothefirst(Bechtel1986).Ishallbrieflydiscusstheminorder.AlthoughErnestNagel’sTheStructureofScience(1961)containsthemosttime-honoredtreatmentoftheoryreduction,RobertCausey’sUnityofScience(1977)probablyprovidesthemostcomprehensivediscussionofthetopic.Theirgeneralapproachtotheoryreductionproceedswithintheconstellationofcommitmentsthatcharacterizelogicalempiricism,includingtheassumptionsthatasatisfactoryaccountofscientificrationalityrequiresheedtojustificatoryconsiderationsonly,thatscientifictheoriesarebestunderstoodascomplexpropositionalstructuresandbestrepresentedviaformalreconstructions,thatscientificexplanationresultsfromthedeductionofexplanandafromscientificlaws,thatscientificprogressresultsfromthesubsumptionofreigningtheoriesbytheoriesofevengreatergenerality,andthatscienceultimatelyenjoysanunderlyingunityoftheoryandontology.Thismodelconceivestheoryreductionasaspecialcaseofdeductive-nomologicalexplanation.Itisaspecialcasebecausetheexplanandumisnotastatementdescribingsomeeventbutratheralawofthereducedtheory.Inordertocarryoutsuchreductions,thepremisesinthemostcomplexcasesofheterogeneousreductiveexplanationsmustinclude(1)atleastonelawfromthereducingtheory:(2)statementsindicatingthesatisfactionoftherequisiteinitialconditionsspecifiedinthatlaw;(3)bridgelawswhichsystematicallyrelate–withinaparticulardomaindelineatedbyappropriateboundaryconditions–thetermsfromthepertinentlaw(s)ofthereducingtheorytothosefromthelawofthereducedtheory;(4)statementsindicatingthesatisfactionofthoseboundaryconditions(underwhichtheeventsdescribedinthelawofthereducingtheoryrealizetheeventsdescribedinthelawofthereducedtheorythatistobeexplained).Suchpremisespermitastraightforwarddeductionofthelawofthereducedtheory.Becausetheboundaryconditionsincludedinthebridgelawsarecastintermsofpredicatescharacteristicofthereducingtheory,thereductionreflectsanasymmetrybetweenthetwotheories.Thereducingtheoryexplainsthereducedtheory,finally,becausethereducingtheoryencompassesawiderarrayofeventswithinitsexplanatorypurview.Thissetofevents,presumably,includesalloftheeventsthereducedtheoryexplainsandmore,sothattheprinciplesofthereducingtheoryarebothmoregeneralandmorefundamental.Themostpopularshowcaseillustrationisthereductionofthelawsofclassicalthermodynamicstotheprinciplesofstatisticalmechanics.

Whenthereducingtheoryoperatesatalowerlevelofanalysisthanthereducedtheory,theaddedgeneralityofitsprinciplesisadirectfunctionofthisfact.Thesearecasesofmicroreductionswherealowerleveltheoryanditsontologyreduceahigherleveltheoryanditsontology(OppenheimandPutnam1958,Causey1977).Microreductionistsholdthatifwecanexhaustivelydescribeandpredictupperlevel(ormacro)entities,properties,andprinciplesintermsoflowerlevel(ormicro)entities,properties,andprinciples,thenwecanreducetheformertothelatterandreplace,atleastinprinciple,theupperleveltheory.Virtuallyalldiscussionsofintertheoreticrelationspresupposethisarrangementamong(andwithin)thesciencesintermsoflevelsofanalysis.(See,forexample,ChurchlandandSejnowski1992,pp.10-11.)Numerousconsiderationscontributetothedepictionofthearchitectureofscienceasalayerededificeofanalyticallevels(Wimsatt1976).Ideally,movingtowardlowerlevelsinvolvesmovingtowardthestudyofincreasinglysimplesystemsandentitiesthatareubiquitous,enduring,andsmall.Conversely,movingfromlowertohigherlevelsciencesinvolvesmovingtowardstudiesoflarger,rarersystemsofgreatercomplexityand(often)lessstabilityandwhosehistoryislessancient.Becausethealtitudeofalevelofanalysisisdirectlyproportionaltothecomplexityofthesystemsittreats,higherlevelsciencesdealwithincreasinglyrestrictedrangesofeventshavingtodowithincreasinglyorganizedphysicalsystems.1Asasimplematteroffact,oftenmorethanoneconfigurationoflowerlevelentitiescanrealizevarioushigherlevelkinds(especiallywhenfunctionallycharacterized).Theresultingmultipleinstantiationshighlightboththeimportanceandthecomplexityoftheboundaryconditionsinthebridgelawsofheterogeneousmicroreductions.Criticsofthemicroreductionistprogram(e.g.,Fodor1975)seethatcomplexityassufficientgroundsforquestioningtheprogram’sfeasibilityinthecaseofthespecialsciences,whilemoresympatheticparticipantsinthesediscussionssuchasRobertRichardson(1979)andtheChurchlands(1990)suggestthatwhenscientiststraceoutsuchconnectionsbetweenhigherandlowerlevelentitiesinspecificdomainstheyvindicatetheoverallstrategy,whilerecognizingthedomainspecificityofitsresults.Reductionistsdifferamongthemselvesastothepreciseconnectionsbetweenentitiesatdifferentlevelsthatarerequiredforsuccessfulreductiveexplanation.Theyallagree,however,thatthetheorieswhicharepartiestothereductionshouldmapontooneanotherwellenoughtosupportsystematicconnections,usuallycontingentidentities,betweensome,ifnotall,oftheentitiesthatpopulatethem.Thetestoftheresultingcontingentidentitiesismet,ultimately,bytheexplanatorysuccessesthereductionsaccomplish(McCauley1981;Enc1983).Feyerabend(1962)andKuhn(1970)arethemostprominentproponentsofthesecondmajoraccountofintertheoreticrelations.Theyforgedtheirearlydiscussionslargelyinresponsetoboththelogicalempiricistprogramanditsreductionistblueprintforscientificprogress.Feyerabendemphasizedhowscrutinyofmanyoftheshowcaseillustrationsofintertheoreticreductionsrevealedthefailureofthesecasestoconformtothelogicalempiricists’model.Kuhndiscussednumerousexamplesinthehistoryofsciencewheresuccessivetheorieswerenotevenremotelyplausiblecandidatesforthesortofsmoothtransitionsthestandardreductivemodelenvisions.Instead,Kuhnproposedthatprogressinscienceconsistsofextendedintervalsofrelativetheoreticalstabilitypunctuatedbyperiodicrevolutionaryupheavals.Bothholdthatthecasesinquestioninvolveconflictsbetweenincommensurabletheories.Althoughthesubsequentliteratureisrifewithassessmentsofthisclaim(Thagard1992offersthemostsuggestiveofrecenttreatments),thecriticalpointfornowisthat,whateverincommensurabilityamountsto,itstandsinstarkoppositiontoanymodelofintertheoretic

relationsthatrequiresneatmappingsbetweentheories’principlesandontologiescapableofsupportingstrictdeductive-nomologicalexplanations.Thehistoryofscienceprovidesampleevidencethatwheresuchincompatibilityissufficientlyseverethetheoryanditsontologythatareeventuallydeemeddeficientundergoelimination.Stahl’ssystemofchemistryisthepreferredillustration,butDarwin’stheoryofinheritancecouldservejustaswell.Theunmistakablesensethatbothofthesemodelsofintertheoreticrelationsdescribesomeactualcasesfairlyaccuratelyandthattheyeachcaptureimportantinsightsabouttheissuesatstake,theirprofoundconflictsnotwithstanding,couldinducepuzzlement.AnaccountofintertheoreticrelationsintermsofacontinuumofcommensurabilitythatPaulChurchland(1979)initiallysketchedandwhichtheChurchlandshavesubsequentlydeveloped(P.S.Churchland1986,pp.281f.;ChurchlandandChurchland1990)substantiallyresolvesthatperplexitybyreconcilingthoseconflictsandallottingtoeachmodelameasureofdescriptiveforce.TheChurchlandspointoutthat,infact,differentcasesofintertheoreticrelationsvaryconsiderablywithrespecttothecommensurabilityofthetheoriesinvolved.So,theyproposethatsuchcasesfallalongacontinuumofrelativeintertheoreticcommensurability,where,ineffect,thetwomodelssketchedaboveconstitutethatcontinuum’send-points.Oneendofthecontinuumrepresentscaseswhereintertheoreticmappingisextremelyloworevenabsent.Thesearecasesofradicalincommensurabilitywhererevolutionaryscienceandthecompleteeliminationofinferiortheoriesensue.Whatevervaguenessmaysurroundthenotionof‘incommensurability,’theChurchlandsareclearlyconfidentthatthedevelopmentswhichbroughtabouttheeliminationofthebodilyhumours,theluminiferousether,caloricfluid,andthelike,involvesufficientlydrasticchangestojustifythesortofextremedeparturesfromthetraditionalmodelofreductionthatKuhnandFeyerabendadvocated.Attheotherendofthiscontinuum,wherethemappingofonetheoryonanotherisnearlyexhaustiveandtheformertheory’sontologyiscomposedfromtheentitiesthelattertheorycountenances,themostrigorousmodelsoftheoryreductionmostnearlyapply(e.g.,Causey1972).Theconstraintsproponentshaveimposedontheoryreductionaresodemandingthatitisafairquestionwhetheranyactualscientificcasequalifies.TheChurchlandshaveurgedconsiderablerelaxationoftheconditionsnecessaryforintertheoreticreduction.Insteadofconformitytotherigorouslogicalandontologicalconstraintstraditionalmodelsimpose,PaulChurchland(1979;seetooHooker1981;Bickle1992)suggeststhatthereducingtheoryneedonlypreservean“equipotentimage”ofthereducedtheory’smostcentralexplanatoryprinciples.Thereductioninvolvesanimage,sincethereducingtheoryneednotduplicateeveryfeatureofthereducedtheory’sprinciples,butonlyenoughoftheirsalientonestosuggesttheirgeneralcharacterandtoindicatetheirsystematicimport(seeSchaffner1967).Thatimageisequipotent,though,sincethereducingtheory’sprincipleswillpossessalloftheexplanatoryandpredictivepowerofthereducedtheory’sprinciples–andmore.Fromthestandpointoftraditionalmodels,Churchlandproposesaformofapproximatereduction,whichfallswellshortofthelogicalempiricists’standards,butwhichalsosuggestshowtruetheories(e.g.,themechanicsofrelativity)cancorrectandevenapproximatelyreducetheoriesthatarefalse(e.g.,classicalmechanics).Switchingtothemetaphorofimageryisappropriate,since,asWilliamWimsatt(1976,p.218)notedoveradecadeago,ifthestandardmodelsofreductionallegethatafalsetheoryfollowsfromatrueone,theputativedeductionhadbetterinvolveanequivocationsomewhere!InrecentyearstheChurchlandshaveeachenlargedonthiscontinuummodel.Forexample,withinhisneurocomputationalprogramPaulChurchlandhasadvancedaprototypeactivationmodelof

explanatoryunderstandingthat,presumably,includestheunderstandingthatarisesfromreductiveexplanations.Churchlandholdsthattheneurocomputationalbasisofexplanatoryunderstandingresidesintheactivationofaprototypevectorwithinaneuralnetworkinresponsetoimpingingcircumstances.Adistributedrepresentationoftheprototypeintheneuralnetworkconstitutesthebrain’scurrentbeststabatdetectinganunderlyingpatternintheblooming,buzzingconfusion.ForChurchlandexplanatoryunderstandingisanarrayofinputsleadingtotheactivationofoneoftheseexistingprototypesasopposedtoanother.Churchlandinsiststhattheactivationofaprototypevectorincreases,ratherthandiminishes,availableinformation.Itinvolvesa“speculativegain”ininformation(1989,p.212).Thus,contrarytoanti-reductionistcaricature,thisaccountofexplanatoryunderstandingimpliesthatreductiveexplanationsamplifyourknowledge.Theoriginalityoftheinsightsareductiveexplanationoffersdependsuponthenovelapplicationofexistingcognitiveresources,i.e.,ofanindividual’srepertoireofprototypevectors.Consequently,reductiveexplanationinvolvesneitherthegenerationofnewschemesnorthedestructionofoldones.Theapproximatecharacterofintertheoreticreductionsisafunctionofthis“conceptualredeployment”onwhichtheyturn(1989,p.237).Inconceptualredeploymentadevelopedconceptualframeworkfromonedomainisenlistedforunderstandinganother.Inshort,successfulreductiveexplanationrestsonananalogicalinferencebyvirtueofwhichwedeemanimageofatheoryequipotenttotheoriginal.Havingestablishedtheinitialapplicabilityofanexisting,alternativeprototypevector,itinevitablyundergoesareshapingasaconsequenceofexposuretothenewlyadoptedtrainingset.Thisreshapingofactivationspaceistheneurocomputationalprocessthatdrivestheremainingco-evolutionofthereductivelyrelatedtheories.Inherdiscussionsoftheco-evolutionoftheories,PatriciaChurchlandhasintroducedadynamicelementintothecontinuummodel.Shesuggeststhatthepositionoftwotheories’relationsonthiscontinuumcanchangeovertimeastheyeachundergoadjustmentsinthelightofoneanother’sprogress.Thesuggestionthatscientifictheoriesco-evolvearisesfromananalogywiththeco-evolutionofspeciesandfromthepictureofthesciencesbrieflyoutlinedabove.Ontheco-evolutionarypicturethesciencesexertselectionpressuresononeanotherinvirtueofageneralconcernforsupplyingasmuchcoherenceaspossibleamongourexplanatoryschemes.Ifthevarioussciencesarearrangedintiersofanalyticallevels,theneachwillstandatvaryingdistancesfromtheothersinthisstructure.Typically,proximityisacentralconsiderationinassessingtheforceofselectionpressures.Thus,thepivotalrelationshipsarethosebetweenascienceandthosesciencesatimmediatelyadjacentlevels.Forexample,thepresumptionisthattheneurosciencesbelowandthesocio-culturalsciencesabovearemorelikelytoinfluencepsychologythanarethephysicalsciences,sincetheyarelocatedbelowtheneurosciencesand,therefore,atanevengreaterdistance.Itisthisprocessoftheco-evolutionoftheoriesandtheChurchlands’accountofitthatwilldominatetheremainderofthispaper.IshallattendtoitsimplicationsfortherelationshipofcognitivepsychologytothesortofneurocomputationalmodelingthattheChurchlandsendorse.3.ThreeWaysTheoriesMightCo-evolvePatriciaChurchland’sNeurophilosophy(1986)containsthemostextensivediscussionofreductionintermsoftheco-evolutionoftheoriesavailable.2Churchlandfocusesontherelationbetween

neuroscienceandpsychology,butherdiscussionclearlyaspirestomoralsthataregeneral.Hercommentsatvariouspointsseemtosupportthreedifferentco-evolutionaryscenarios,thoughtwoofthemare,quiteclearly,closelyrelated.ThethreearedistinguishedbythelocationsontheChurchlands’continuumtowhichtheypredictco-evolvingtheorieswillincline.OnsomeoccasionsChurchlandsuggeststhatpsychologyandtheneuroscienceswillco-evolveinthedirectionofapproximatereduction.Shestates,forexample,that“theco-evolutionarydevelopmentofneuroscienceandpsychologymeansthatestablishingpointsofreductivecontactismoreorlessinevitable....Theheartofthematteristhatifthereistheoreticalgiveandtake,thenthetwoscienceswillknitthemselvesintooneanother”(1986,p.374).Themetaphoroftwosciencesknittedintooneanotherimpliesanintegrationthatistight,orderly,anddetailed.AlthoughChurchland,presumably,doesnotthinkthatthatintegrationwillsatisfythetraditionalmicroreductionists’stringentdemandsonintertheoreticmapping,talkofknittingtwosciencesintooneanother,theon-goingpursuitofaunifiedmodelofreduction(ChurchlandandChurchland1990),andanewinterestinestablishingpsycho-physicalidentitiesechocommitmentsoftraditionalmicroreductionism,wherethesortofreductivecontactinquestionledtotalkofan“inprinciplereplaceability”ofthereducedtheoryinwhichthelowerleveltheoryenjoysbothexplanatoryandmetaphysicalpriority.Morerecently,theChurchlandshavebeenclearaboutthefutilityofattemptstoreplaceupperleveltheories,buttheystillgenerallysubscribetotheexplanatoryandmetaphysicalpriorityofthelowerleveltheory–especiallyinthecaseofpsychologyandneuroscience.(See,forexample,P.S.Churchland1986,pp.277,294,and382.)Certainly,aco-evolutionaryaccountofintertheoreticrelationshasnoproblemtranslatingthegeneralmicroreductiveimpulse.Withinthisframeworkitamountstotheclaimthattheselectionpressuresthatthescienceatthelevelofanalysisbelowthatofthetheoryinquestionexertswillhaveanoverwhelminglygreatereffectonthattheory’seventualshapeandfatethanwillthesciencesabove(seesection5).OntheChurchlands’account,suchintertheoreticintegrationwouldenabletheneurosciencestosupplyanequipotentimageofpsychologicalprinciples.PaulChurchland’sspeculationsabouttheneuralrepresentationofthesensoryqualiaassociatedwithcolorvisionmightconstituteanappropriateillustration.Thefitbetweenourcommonsensenotionsaboutourexperiencesofcolorsandthesystemofneuralrepresentationheproposesisquiteneat(1989,p.102-08).HereafterIshallrefertothissenseoftheco-evolutionoftheoriesas“co-evolutionM,”i.e.,co-evolutioninthedirectionofapproximatemicroreduction.IntheChurchlands’jointdiscussion(1990,chapter6.1),whereitplaysbothapredictiveandnormativerole,thisnotionofreductionreceivesconsiderableattention.TheChurchlandsclearlyholdthat“itisreasonabletoexpect,andtoworktoward,areductionofallpsychologicalphenomenatoneurobiologicalandneurocomputationalphenomena”(1990,p.249).Co-evolutionMisnottheonlyaccountofco-evolutioninNeurophilosophy,for,astheChurchlandshavesubsequentlyasserted,inthecaseofpsychologyandneuroscience,“thereareconflictingindications”aboutthedirectioninwhichconjecturesatthesetwolevelsofanalysiswilllikelyco-evolve(1990,p.253).Ifintegrationisthefateofpsychologyandneuroscience,PatriciaChurchlandrepeatedlyhintsthatthiswillonlyoccurafterpsychology’sinitialdemolitionandsubsequentreconstructioninaccordwiththemandatesoftheneurosciences.Sheclaims,forexample,that“...thepossibilitythatpsychologicalcategorieswillnotmaponetooneontoneurobiologicalcategories...doesnotlooklikeanobstacletoreductionsomuchasitpredictsafragmentationandreconfigurationofthepsychologicalcategories”(1986,p.365).Withthissecondview,aswiththefirst,noquestionarisesaboutwheretheblamelies,ifthetheoriesofpsychologyandneurosciencefailtomapontooneanotherneatly.(SeeWimsatt1976.)Atleastfortheshortterm,Churchland

seemstoexpectthatthisintertheoreticrelationwillmigrateinjusttheoppositedirectiononthecontinuumofintertheoreticcommensurabilityfromwhatco-evolutionMpredicts,i.e.,towardagrowingincommensurabilitythatpredictsafragmentationofpsychologicalcategories.Ifthe“fragmentationandreconfiguration”ofpsychologicalcategoriesinvolvedonlytheelaborationoradjustment(oreventheinprinciplereplaceability)ofpsychologicaltheoriesbydiscoveriesintheneurosciences,co-evolutionMmightsuffice.Onthissecondview,though,thisprocesscanleadtotheeventualeradicationofmajorpartsofpsychology.So,forexample,Churchlandremarksthat“thereisatendencytoassumethatthecapacitiesatthecognitivelevelarewelldefined...inthecaseofmemoryandlearning,however,thecategorialdefinitionisfarfromoptimal,andrememberingstandstogothewayofimpetus”(1986,p.373,emphasisadded3).HereChurchlandanticipatesthatjustasthenewphysicsofGalileoandhissuccessorsoustedthelatemedievaltheoryofimpetus,sotooshalladvancesinneurosciencedisposeofpsychologists’speculationsaboutmemory.This,then,isco-evolutionS(co-evolutionproducingtheeliminationsoftheoriescharacteristicofscientificrevolutions)inwhichthetheoreticalperspectivesoftwoneighboringsciencesaresodisparatethateventuallythetheoreticalcommitmentsofonemustgo--inthefaceoftheother’ssuccess.Co-evolutionSunderliesthepositionforwhichtheChurchlands’advocacyhasbeenfamous,viz.,eliminativematerialism.4Theyhavecontendedthatprogressintheneuroscienceswillprobablybringabouttheeliminationoffolkpsychologyaswellasanyotherpsychologicaltheoriesthatinvolvecommitmentstothepropositionalattitudes(presumably,includingmuchofmainstreamcognitiveandsocialpsychology).Justasscientistsbanishedphlogistonandcaloricfluid,sotoowillthepropositionalattitudesbeexpelledasneuroscienceprogresses.Thepsychologicalconjecturesinquestion(will)failtomatchthedescriptive,explanatory,andpredictivesuccessesoftheirneuroscientificcompetitors.Moreover,theirsubstantialdissimilaritiestothoseallegedcompetitorsprecludeanysortofreconciliation.Consequently,numeroustheoreticalnotionsinpsychologystandtogothewayofimpetus.ThisisthepredictedresultwhentheChurchlandsemphasize,amongthose“conflictingindications,”theuncongenialrelationsbetweenpsychologyandneuroscience.Revisingtheirextremeeliminativism,theChurchlandssometimesseemtointendthesetwointerpretationstoaddressdifferentstagesintheco-evolutionaryprocess(asIsuggestedabove):first,thedemolitionofmuchcurrentpsychologyviaco-evolutionSfollowedbythereconstructionofaneuroscientificallyinspiredpsychologyviaco-evolutionM.Thecrucialpointfornowisthatthesetwointerpretationsofco-evolutionholdthattherelationshipbetweentwotheorieswill,overtime,shiftinonedirection(asopposedtotheother)ontheChurchlands’continuum.Anobviousquestionarises,though.Ifeitherdirectionispossible,thenwhatarethevariablesthatdeterminethedirectionofanyshift?(Thisquestionpressestherevisedversionofeliminativismnolessthantheoriginal.)TheChurchlandshavenotaddressedthisquestiondirectly,becausetheyhaverecognizedthatthecomplexitiesoftheintertheoreticrelationsinquestionandoftherelationshipofpsychologyandneuroscience,inparticular,requiremore.Enterthethirdinterpretation.OneofPatriciaChurchland’sextendedcommentsabouthergeneralmodelofreduction(1986,pp.296-7)isespeciallyrevealing,sinceitreflectsatvariouspointstheinfluenceofallthreeinterpretations.

...somemisgivingsmaylingeraboutthepossibilityofreductionshoulditbeassumedthatareductivestrategymeansanexclusivelybottom-upstrategy...

Thesemisgivingsarereallyjustbugbears,andtheyhavenoplaceinmyframeworkforreduction. ...ifthereductionissmooth,itsreductiongivesit[thereducedtheory]–anditsphenomena–afirmerplaceinthelargerscheme...Ifthereductioninvolvesamajorcorrection,thecorrected,reducedtheorycontinuestoplayaroleinpredictionandexplanation...Onlyifonetheoryiseliminatedbyanotherdoesitfallbythewayside. ...coevolution...iscertaintobemoreproductivethananisolatedbottom-upstrategy.

Thesecondparagraphtracespointsonthecontinuum.Italludesinitiallytoco-evolutionM–itsfinalsentencetoco-evolutionS.Itisthefirstandthirdparagraphs,though,whereshadowsofathirdinterpretationappear.Closelyrelatedtoco-evolutionMisco-evolutionP(co-evolutionasexplanatorypluralism).Theirmanysimilaritiesnotwithstanding,itisworthteasingthemapart.Asafirstpass,whereco-evolutionManticipatesincreasingintertheoreticintegrationlargelyguidedbyandwithadefaultpreferenceforthelowerlevel,co-evolutionPconstruestheprocessaspreservingadiversesetofpartiallyintegratedyetsemi-autonomousexplanatoryperspectives–wherethatnon-negligiblemeasureofanalyticalindependencerestsateachanalyticallevelontheexplanatorysuccessandtheepistemicintegrityofthetheoriesandonthesuggestivenessoftheempiricalfindings.Co-evolutionM,ineffect,holdsthatselectionpressuresareexertedexclusivelyfromthebottomup,whereasco-evolutionPattendstotheconstraintsimposedbytheneedsanddemandsoftheoriesoperatingathigherlevels.Theseapparentlysmalldifferencesarebutthefringeskirmishesofsomeofthemostbasicepistemologicalandmetaphysicalbattlesinthephilosophyofscience.Spacelimitationsprecludeextensivedevelopment,butbroadly,iftheyarenotpersuadedbyco-evolutionS,physicalistspreferco-evolutionM,sinceitsuggestsascienceunifiedinboththeoryandontologythataccordsprioritytothelower(i.e.,physical)levels.Morepragmaticallymindedphilosophersoptforco-evolutionP,foregoingassurancesofandworriesaboutaunifiedscienceandmetaphysicalpurityinfavorofenhancedexplanatoryresources.FornearlyadecadenowtheChurchlandshavebeennegotiatingtheirinterestsinunifiedscienceandmetaphysicalpurityontheonehandwiththeirinterestsinenhancedexplanatoryresourcesandinternalismontheother.(SeeMcCauley1993andnote10below.)Therelaxationoftheireliminativismandtheiremergingpreferenceforco-evolutionPindicatetheinfluenceofpragmaticcurrentsintheirthought.Co-evolutionPisprominentinNeurophilosophyandevenmoresosince.5PatriciaChurchlandclaimsthat“...thehistoryofsciencerevealsthatco-evolutionoftheorieshastypicallybeenmutuallyenriching,”that“[r]esearchinfluencesgoupanddownandalloverthemap,”that“co-evolutiontypicallyis...interactive...andinvolvesonetheory’sbeingsusceptibletocorrectionandreconceptualizationatthebehestofthecohorttheory,”andthat“psychologyandneuroscienceshouldeachbevulnerabletodisconfirmationandrevisionatanylevelbythediscoveriesoftheother”(1986,pp.363,368,373,and376).Figure6.2.1seemsthemostplausibleinterpretationoftherelationshipbetweenthesethreenotionsofco-evolutionandtheearliercontinuummodel;itroughlyindicatestheregionsofthatcontinuumwherethecasescoveredbythethreetypesofco-evolutionendup.(SeeChurchlandandChurchland1990,p.252.)

Figure6.2.1.Threenotionsofco-evolutionsituatedontheChurchlands’continuum.

Section4willsuggestthatthepictureinFigure6.2.1ofintertheoreticrelationsandofco-evolution,inparticular,isoversimplifiedtothepointofdistortion.Theintertheoreticdynamicsofscientificrevolutionsarequitedifferentfromthoseofapproximatemicroreductionandexplanatorypluralism.Crucially,co-evolutionPisincompatiblewithco-evolutionS.Themutualintertheoreticenrichmentco-evolutionPenvisionswillnotarise,ifneuroscienceisradicallyreconfiguring(letaloneeliminating)psychology.Neitherthehistoryofsciencenorpragmaticaccountsofscientificpracticeoffermuchreasontothinkthatco-evolutionSprovideseitheranaccuratedescriptionorausefulnormfortherelationshipbetweenpsychologyandneuroscienceorforanysuchrelationshipbetweentheoriesinsciencesoperatingatdifferentanalyticallevels.Thedifferencesbetweenco-evolutionP’sandco-evolutionMarealsoimportant.Atstakeisthequestionoftherelativepriorityofneuroscientific(lowerlevel)andpsychological(upperlevel)contributionstothescienceofthemind/brain.Thistopicwilldominatesection5.Incriticizingco-evolutionSandcurtailingco-evolutionM,theaimofthenexttwosectionsis,ultimately,toendorseanddevelopthenotionofexplanatorypluralism.4.ExploringExplanatoryPluralism:DebunkingCo-evolutionsEnlistingadistinctionWimsatt(1976)introducedbetweenintralevelandinterlevelcontexts,Ihavepreviouslydevelopedamodelofintertheoreticrelationsthatdiscloseswhyweshouldnotexpectadvancesinneurosciencetoeliminatemuchpsychologydirectly(McCauley1986).Moregenerally,itsuggeststhatco-evolutionSdoesnotveryhappilymodeltheco-evolvingrelationsoftheoriesatdifferentlevels.Thesortsofunequivocaleliminationsoftheoriesandontologiesthatco-evolutionScountenancesariseinintralevelcontextsinvolvingconsiderableincommensurability.Thesecontextsconcernchangeswithinaparticularscienceovertime.Theyincludetheclassiccasesthatphilosophersgroupundertherubricof“scientificrevolutions”–impetus,phlogiston,caloricfluid,andthelike.Withinaparticularlevelofanalysissomenewlyproposedtheoryprovessuperiortoitsimmediatepredecessorwithwhichitissubstantiallydiscontinuous.Whenthescientificcommunityoptsforthisnewtheory,mosttracesofitspredecessorrapidlydisappear.Sincetheyofferincompatibleaccountsofmanyofthesamephenomena,thenewtheoryexplainstheoldtheoryaway.Bycontrast,intralevelsituationswherethemappingsbetweentheoriesarereasonablygoodfallneartheotherendoftheChurchlands’continuum.Herethenewtheoryexplainsitspredecessorwhichitalsotypicallycorrects.Scientistsregardtheearliertheory’sdomainasaspecialcasetowhichthenewtheoryappliesandforwhichtheoldtheorycontinuestosufficeasauseful

calculatingheuristic.Althoughcorrectedandincorporatedasaspecialcaseintoamoregeneraltheory,Newton’slawsofmotionworkwellformostpracticalpurposes.Anewtheorydisruptssciencelesstotheextentitpreserves(ratherthanoverthrows)thecherishedinsightsandconceptualapparatusofitspredecessors.Itmayrequirereinterpretationofestablishednotions(“planets,”“genes,”“grammaracquisition,”etc.),butchangesareevolutionaryonlywhentheypreserveafairmeasureofintensionalandextensionaloverlapwiththeirpredecessors.Whensucceedingtheoriesinsomesciencearelargelycontinuous,noonespeaksofelimination.Thechangeisevolutionary,notrevolutionary.Consequently,thenewtheoryisperfectlycapableofprovidinganequipotentimageoftheold.Thesearethecaseswherethenewtheoryoverwhelminglyinheritstheevidencefortheold.Revolutionaryorevolutionary,progresswithinsomescienceeliminatesfeaturesofearliertheorieseventually.Inrevolutionarysettingsthechangesareabruptandtheeliminationis(relatively)immediate.Inevolutionarycontextsincompatibilitiesaccrueovertime.Althoughthetransitionfromonetheorytoitsimmediatesuccessormaybemoreorlesssmooth,overaseriesofsuchtransitionsalltracesofancestraltheoriesmaycompletelydisappear.Considerthefateof“naturalmotions”fromAristotelianthroughNewtonianmechanics(McCauley1986,pp.192-93).Similarly,overthepasthundredyearsthe“memorytrace”hasundergoneconsiderableevolutionarytransformation.Sometheoristswouldarguethatthereinterpretationshavebeensosubstantialthattheoriginalnotion(andwhatitallegedlyreferredto)hasvirtuallyvanished.6Interlevelrelationsconcerntheoriesatdifferent(typicallyneighboring)levelsofanalysisataparticularpointintime(incontrasttointralevelcasesconcernedwithsuccessivetheoriesatthesamelevelofanalysis).TheChurchlands’continuummapsontointerlevelcasestoo.Whensciencesatadjoininglevelsenjoysubstantialintertheoreticmapping(insituationsapproximatingclassicmicroreductions)theyheavilyconstrainoneanother’sform–otherwise,whywouldanyonehaveattemptedtocharacterizetheirrelationsintermsofdeductivelogicandidentitystatements?Thisistheeffectoftheknittingoftwosciencesintooneanotherthatco-evolutionMenvisions.Awellintegratedlowerleveltheoryhasresourcessufficienttoreproducetheexplanatoryandpredictiveaccomplishmentsofthecorrespondingupperleveltheory,however,thisoftencomesatconsiderablecomputationalexpense.AstheChurchlandshaveemphasized,thisdoesnotdisgracethehigherleveltheorynorleadtotheevaporationofthephenomenaitseekstoexplain.Whenconsideringinterlevelcaseswithrelativelyunproblematicintertheoreticrelations,theChurchlands,likethetraditionalreductionistsbeforethem7,havefocusedexclusivelyontheirresemblancestotheintralevelsettingsdescribedabove.(See,forexample,P.S.Churchland1986,p.294.)Afterall,heretootheelaborationsoftheupperleveltheory’scentralconceptsthatthelowerlevel,reducingtheoryoffersoftencorrectthelessfine-grained,upperleveltheory’spronouncements.However,becausethetheoriesaretightlyknit,theupperleveltheorystillprovidesausefulandefficientapproximationofthelowerleveltheory’sresults.Thissoundsquitelikethecasesofscientificevolutiondescribedabove.Beneaththeseresemblances,though,liesmallbutrevealingdifferences.First,unliketheevolutionaryintralevelcases,thereducedtheoryininterlevelsituationsdoesnotstandinneedoftechnicalcorrectionineverycase.Forafewsituationsatleast,itsresultswillconformpreciselywiththoseofthelowerleveltheory,becauseforthesecasesitadequatelysummarizestheeffectsofallrelevantlowerlevelvariables.8Thiscontrastswiththeinescapable,ifoftennegligible(froma

practicalstandpoint),divergenceofthecalculationsofsometheoryanditssuccessor,suchasclassicalmechanicsandthemechanicsofrelativity.(SeeChurchlandandChurchland1990,p.251.)Ininterlevelcasescorrectionscanarisebecausetheupperleveltheoryisinsufficientlyfine-grainedtohandlecertainproblems.Bycontrast,inintralevelcasescorrectionsalwaysarisebecausetheearliertheoryiswrong–byalittleinevolutionarycases,byalotinrevolutionaryones.Itfollowsthattheupperleveltheoryisnotalwaysamerecalculatingheuristic(asthereplacedpredecessorisincasesofscientificevolution).Moreover,theupperleveltheory’sheuristicadvantagesinwellintegratedinterlevelcontextsaretypicallyenormous,comparedwithintralevelcases.Thedivergenceofcomputationaleffortbetweentheclassicalandstatisticalsolutionsforsimpleproblemsaboutgases(aninterlevelcase)dwarfsthatbetweenclassicalmechanicsandthemechanicsofrelativityforsimpleproblemsaboutmotion(anintralevelcase).Ofapiecewiththisobservation,theChurchlandsquiteaccuratelydescribethequantumcalculationsofvariouschemicalproperties(anotherinterlevelcase)as“daunting”(1990,p.251).Finally,theupperleveltheorylaysoutregularitiesaboutasubsetofthephenomenathatthelowerleveltheoryencompassesbutforwhichithasneithertheresourcesnorthemotivationtohighlight.Thatisthepriceofthelowerleveltheory’sgeneralityandfinergrain.Iftheseconsiderationsarenotcompelling,scrutinyofinterlevelcircumstancesthatsupportrelativelylittleintertheoreticmappingrevealsfarmoreimportantgroundsforstressingthedistinctionbetweeninterlevelandintralevelsettings.Heretwosciencesatadjacentlevelsaddresssomecommonexplanandaunderdifferentdescriptions,buttheirexplanatorystoriesarelargely(thoughnotwholly)incompatible.OntheChurchlands’view,thisisjusttherelationshipbetweenneuroscienceandmostoffolkpsychology,andifrememberingistogothewayofimpetus,therelationshipbetweenneuroscienceandsomeimportantpartsofscientificpsychologyaswell.Ifalloftheseintertheoreticrelationsshouldreceiveaunifiedtreatment,astraditionalreductionists,theChurchlands(e.g.,ChurchlandandSejnowski1990,p.229),andFigure6.2.1suggest,thenitisperfectlyreasonabletoexpecteliminationinthoseinterlevelsituationsinvolvingsignificantincommensurability.Theproblem,though,isthatneitherthehistoryofscience,norcurrentscientificpractice,northescientificresearchtheChurchlandschampion,noraconcernforexplanatorypluralismoffersmuchreasontoexpecttheoryeliminationinsuchsettings.Incommensurabilityininterlevelcontextsneitherrequirestheeliminationoftheoriesonprincipledgroundsnorresultsinsucheliminationsinfact.Admittedly,intheearlystagesofascience’shistoryitisnotalwayseasytodistinguishlevelsofanalysisand,consequently,todistinguishwhatwouldcountasaninterlevel,asopposedtoanintralevel,elimination.Crucially,though,thehistoryofscienceandespeciallythehistoryoflatenineteenthandtwentiethcenturyscienceoffernoexamplesoflarge-scaleinterleveltheoryelimination(particularlyofthewholesalevarietystandardeliminativismandco-evolutionSenvision)oncetheupperlevelscienceachievessufficienthistoricalmomentumtoenjoytheaccoutrementsofotherrecognizedsciences(suchascharacteristicresearchtechniquesandinstruments,journals,universitydepartments,professionalsocieties,andfundingagencies).Thereasonissimpleenough.Maturesciencesarelargelydefinedbytheirtheoriesand,moregenerally,bytheirresearchtraditions(Laudan1977),hence,eliminationofanupperleveltheorybyalowerleveltheorymayrisktheeliminationoftheupperlevelscientificenterprise!(Presumably,thisiswhyNagelalwaysspokeofthereductionofascience,ratherthanofatheory,whenaddressinginterlevelcases.)Amotiveforundertakinginterlevelinvestigation(especiallywhentheintertheoreticconnectionsarenotplentiful)istoexploreonescience’ssuccessfulproblemsolvingstrategiesasameansofinspiringresearch,provokingdiscoveries,andsolvingrecalcitrantproblemsatanotherlevel.

(BechtelandRichardson1993focusinparticularontheproblemofunderstandingtheoperationofmechanisms.)Monitoringdevelopmentsintheoriesatneighboringlevelsisoftenafruitfulheuristicofdiscovery.Thestrategy’sfruitfulnessdependspreciselyonthetwosciencesmaintainingameasureofindependencefromoneanother.Thisisthemarkofexplanatorypluralismandco-evolutionP.Apaucityofinterlevelconnectionsonlyenhancesthe(relative)integrityandautonomyoftheupperlevelscience.AsWimsattnotes“ininterlevelreduction,themoredifficultthetranslationbecomes,themoreirreplaceabletheupperleveltheoryis!Itbecomestheonlypracticalwayofhandlingtheregularitiesitdescribes”(1976,p.222).Thetheoriesatthetwolevelspossessdifferentconceptualandexplanatoryresources,whichunderscoredifferentfeaturesoftheircommonexplanandum.Theyprovidemultipleexplanatoryperspectivesthatshouldbejudgedonthebasisoftheirempiricalsuccess--notonhopesabouttheirputativepromiseforthetheoretical(orontological)unificationofscience.Forthepragmaticallyinclined,explanatorysuccessisbothsufficientlyvaluableandrarethatitwouldbeimprudenttoencouragetheeliminationofanypotentiallypromisingavenueofresearch.AsChurchlandandSejnowskiremark,“theco-evolutionaryadviceregardingmethodologicalefficiencyis‘letmanyflowersbloom’”(1992,p.13).TheChurchlandshavearguedfamously,though,thatfolkpsychologyisbarren(P.S.Churchland1986,pp.288-312andP.M.Churchland1989,pp.2-11).Thoseargumentshaveprovokedanentireliteratureinresponse(seeGreenwood1991andChristensenandTurner1993).IamsympatheticwiththeChurchlands’arguments,atleastwhentheywieldthemagainstpositionsinthephilosophyofmindthatdenytheexplanatorygoalsandtheconjecturalandfalliblecharacteroffolkpsychology.Thatfolkpsychologyoffersexplanationsandthatitisconjecturalandfalliblearebothcorrect.Thatisjustnotthewholestory,though.Thepivotalquestionforapragmatistiswhetherfolkpsychologycancontributetotheprogressofourknowledge,or,better,whetherfolkpsychologycontainsresourcesthatmayaidsubsequent,moresystematicpsychologicaltheorizing.Attributiontheory,thetheoryofcognitivedissonance,andotherproposalswithinsocialpsychologyemployasrichversionsofthepropositionalattitudesasdoesfolkpsychology(BechtelandAbrahamsen1993).Moreover,asDennett(1987)hasemphasized,employingtheintentionalstanceaidstheorizingaboutoperativesubsystemsinsub-personalcognitivepsychology.9Thesearejusttwofrontswherepsychologicalscienceseemstobesimultaneouslyemployingand,eversogradually,transformingfamiliarfolkpsychologicalnotions.Arguably,then,theChurchlandsmayhaveunderestimatedthepossiblecontributionoftheresourcesoffolkpsychology,becausetheyhavebeeninsufficientlyattentivetotheirroleinsocialpsychologicalandcognitivetheorizing(McCauley1987,1989).Indeed,theysometimesdisregardthepsychologicalaltogether.10(See,however,note14below.)Isuspectthatsuchneglectisbornofinsistingonaunifiedaccountofintertheoreticrelationsandofentertainingimagesofco-evolutionS,inparticular.TheChurchlandsarecorrecttoemphasizethesalientroleoftheoryeliminationinscientificprogress,buttheseeliminationsareintralevelprocessesandmostunivocallyso(1)whenthelevelsinquestionconcernscientificpursuitsaswellestablishedasneuroscienceandpsychologyand(2)whenthoselevelsareconstruedasthickly,i.e.,asinclusively,asthedistinctionbetweenthosetwosciencesimplies.ThetheoriesandcharacteristicontologiesinformingStahl’saccountofcombustionandYoung’saccountofthepropagationoflightwerereplacedbytheories(withnewontologies)thatoperatedatthesamelevelsofanalysisandthatwereidentified,bothnowandthen,ascontinuationsoftheresearchtraditionsassociatedwiththoselevels.Eliminationinscienceisprincipallyanintralevelprocess.

Thatisnottoassertthatinterlevelconsiderationsplaynorole.Evenwithlevelsofanalysissothicklyconstrued,Idonotmeantodenythatscientists’decisionsatlevelsaboveandbelowinfluencetheoreticaldevelopmentsatagivenlevel.NordoIwishtodenythatatthattargetedlevelsuchdevelopmentscaninvolveeliminations.Rather,thecriticalpointisthattheseinfluencesarereliablymediatedbydevelopmentsintheconceptualapparatusandresearchpracticesthatareassociatedwiththeresearchtraditionofthetargetedlevel.(SeeBechtelandRichardson1993,especiallychapter8andBechtel,1996.)Ifitisconstruedasanexplanatoryconstruct,then,IagreewiththeChurchlandsthatmuchoffolkpsychologymaywellundergosubstantialrevisionand,perhaps,eveneliminationeventually.11WhatIamsuggesting,though,is:(1)thatthosechangeswilloccurprimarilyasaresultofprogresswithinsocialandcognitivepsychology,i.e.,thattheywillariseastheconsequenceofintralevelprocesseswithinthepsychologicallevelofanalysis;(2)that,invirtueoftheroleofintentionalattributionsinthetheoriesofsocialandcognitivepsychology,thisdisplacementwillprobablybequitegradual,i.e.,that,sofar,thechangesareprovingevolutionary,notrevolutionary;(3)thattheoreticaldevelopmentswithinthosesub-disciplinesofpsychologywillmediatewhateverco-evolutionaryinfluenceneurosciencehasinthisoutcome.MappingtheChurchlands’continuumontotheintralevel-interleveldistinctionyieldsthearrangementinFigure6.2.2.Itreadilyaccommodatesco-evolutionMandco-evolutionP,butco-evolutionSfindsnoobvioushome.Thepointisthattheinteractionofpsychologyandneuroscience,likeallco-evolutionarysituations,isacaseofinterlevelrelations.Inshort,co-evolutionSembodiesacategorymistake.Itconflatesthedynamicsoftheco-evolutionoftheoriesatdifferentlevelsofanalysiswiththoseofscientificrevolutions,whichareintralevelprocesses.12

Figure6.2.2.Mappingdegreesofintertheoreticcontinuity(theChurchlands’continuum)ontointralevelandinterlevelcontexts.

WhatfollowsonthisrevisedpictureinFigure6.2.2aboutinterlevelcasesthatreflectsubstantialincommensurability?Infact,Ithinksuchcasesareextremelyrare,especiallyifthesciencesin

questionarewellestablished,sincepartofbecomingawell-establishedscienceispreciselytopossesstheoriesthatrecognizablycoherewithatleastsomefeaturesoftheoriesatcontiguouslevels.Arguably,thedistinctionsbetweenlevelsofanalysisalreadypresumetheextremeimprobabilityofsuchradicalincompatibilitybetweentheoriesoperatingatadjoiningscientificlevels.(Ofcourse,notallexplanatorytheoriesarescientifictheories.)Ifanalysesdivergeinnearlyallrespects,thenitmaynolongerbeclearthattheyshareacommonexplanandum–temptingsomeresearcherstoadoptobscurantiststrategiesofmetaphysicalextravagance.13Theproblemssurroundingco-evolutionSnotwithstanding,inelaboratingWimsatt’smetaphoroftheco-evolutionoftheoriestheChurchlandshavefundamentallyreinvigoratedthestudyofchangeininterlevelrelationsovertime(arguablyinitiatedinSchaffner1967).Aswiththissection,thenextwillsaymoreaboutco-evolutionPbyopeningwithmoreaboutwhatitisnot.5.ExploringExplanatoryPluralism:BeyondCo-evolutionmThedemandinscienceforcoherenceoftheoriesatadjacentlevelsofanalysisisanadditionalmotive,beyondthepromiseofnewdiscoveries,forprobingpossibleinterlevelconnections.Themotiveistoascertainwhetherornotresearchatnearbylevelscohereswithandsupportsscientists’findings,andifitdoesnot,toexplorepossibleadjustmentstoincreasetheprobabilityofsuchmutualsupport.Thiscan,amongotherthings,clarifyrespectsinwhichthetwosciencesshareacommonexplanandum.Inthelongtermscientists’concernforcoherenceamongtheirresultsinevitablytendstoencouragebetterintertheoreticmappingininterlevelsettings.Forgingsuchconnectionsproducesnewdiscoveriesintherespectivesciences.Onestrategy,thoughcertainlynottheonlyone,istoadvancehypotheticalidentitiesbetweentheoreticalontologiesinordertopoweranengineofdiscovery.TherelationshipbetweenMendeliangeneticsandbiochemicalgeneticsoverthefirsthalfofthiscenturyisanespeciallyaptillustrationoftworelatedresearchprogramsatneighboringlevelsofanalysisaidingoneanotherthroughtheinvestigationofaseriesofproposalsaboutwhichstructureswere,infact,thegenes.Scientists’twoprimarymotivesforinquiriesintoresearchatneighboringlevels,then,arefinallyoneandthesame.Thismightseemtosuggestthatco-evolutionMpredominates;however,anumberofcountervailingconsiderations(someofwhicharebrieflyexaminedinthissection)favoranexplanatorypluralismwherethesciencesmaintainsomeindependenceoftheory,method,andpractice.So,evenapproximatemicroreductionneednotbeinevitable.Twoissuesespeciallydistinguishco-evolutionMandco-evolutionP.Thefirstconcernstherelativemetaphysical,epistemic,and/orexplanatorypriorityofupperandlowerleveltheoriesintheco-evolutionaryprocess.Thesecondconcernsthegroundsofferedforanydisparateassignmentsofthesepriorities.Thedefaultassumptionadoptedinananalysisofco-evolutionMthataccordswiththetraditionalmicroreductionisticrationaleforphysicalismattributescomprehensiveprioritytolowerlevels.Classicalmicroreductionwouldforecastaco-evolutionaryprocesswheretheoverwhelmingmajorityoftheselectionpressuresareexertedfromthebottomup.Theupperleveltheorymaycontributeintheprocessofdiscovery,providinganinitialvocabularyandproblemsforresearch,butsoonerorlateritmustconformtothelowerleveltheory’sexpectations.Herethegroundsforthispriorityrestnotmerelyonthetheoreticalmaturityandsuperiorprecisionlowerleveltheoriestypicallyenjoy(withwhichpragmatismhasnocomplaint)butalsoonpresumptionsaboutthosetheories’metaphysicalpreeminence.(Seenote10above.)

Occasionally14,theChurchlandsseemtosubscribetoaversionofco-evolutionMthatresemblesthisposition.Forexample,ChurchlandandSejnowskiemphasize“theimportanceofthesingleneuronmodels[amongthevarioussub-levelsofanalysiswithinneuroscience]asthebedrockandfundamentintowhichnetworkmodelsmusteventuallyfit”(1992,p.13,emphasisadded).15AlthoughtheChurchlandshaveavoidedthetraditionalmicroreductionists’fervoraboutthereplaceabilityofthereducedtheoryattheupperlevel(e.g.,ChurchlandandChurchland1990,p.256),theirrepeatedemphasisonlowerleveltheories’correctionsofupperleveltheoriesalsosuggeststhatselectionpressuresarelargelyunidirectional,especiallywhentheytreattheselowerlevelelaborationsasofapiecewithcorrectionsinintralevelcontextswheresubstantialontologicalmodificationissometimespartofthepackage.Co-evolutionMwillproverelevanttobutasmallpercentageofcases,atbest.Ontheonehand,ifco-evolutionMissupposedtoissueintheclassicalmicroreductionistprogram(presumably,itisnot),thenallofthefamiliarobjectionsandcaveatsapply–plusatleastoneimportantadditionalone.Thesortoftightintegrationwithadominantlowerleveltheorytowhichclassicalmicroreductionaspiresmustinevitablyrestrictresearchatthehigherlevel.Ifthereeverwasamicroreductionthatconformedtoallofthelogicalandontologicalconstraintsimposedbytheclassicalmodel,forexampleCausey’s(1977)version,itwouldendowthelowerlevelwithanexplanatoryandmetaphysicalprioritythatwoulddiscourageallmotivesfortheoreticalnoveltyatthehigherlevel.Itwouldencourageonlythosepathsofresearchatthehigherlevelthatpromisedtopreserveitstightfitwiththetheoryatthelowerlevel.Itseffect,inshort,wouldbetocheckimaginativescientificproposals.Ontheotherhand,ifco-evolutionMissupposedtoresultonlyintheweakeranalogicalrelationtowhichtheChurchlands’modelofapproximatereductionlooks,thenthepointsofreductivecontactmayprovelessextensivethantheknittingmetaphorsuggests,andthemicroreductionistcasefortheexplanatory,epistemic,andmetaphysicalpriorityoflowerlevelsendsupseemingsomewhatlesscompelling,especiallyoncewehaveteasedapartthedifferencesinthe“corrections”thatoccurininterlevelandintralevelcontexts.Thecaseforco-evolutionP,however,doesnotturnexclusivelyontheproblemsthetwocompetingconceptionsface.Scrutinyofactualcases,includingthoseincognitiveneurosciencetowhichtheChurchlandshavedevotedparticularattention,stronglysuggeststhattheoutcomeoftheco-evolutionoftheoriesisusuallyasco-evolutionPdescribes.Insteadofdrivinginexorablytowardcomprehensivetheoreticalandpracticalintegrationwherethelowerleveltheorygoverns,scientificopportunismisusuallyclosertothetruthinmostinterlevelforays.Atleastinitially,scientistsperiodicallymonitordevelopmentsatnearbylevelssearchingforeitherinterlevelsupport,tantalizingfindings,orboth.ChurchlandandSejnowski’ssurveyofproposalsconcerningtheneuralbasisofworkingmemoryisafittingillustration(1992,pp.297-305).Notonlydidtheconceptof“workingmemory”emergeoutoftheoreticaldevelopmentsinexperimentalpsychology,butsodidmanyofthefindingsthatguideneuralmodeling.Forexample,ChurchlandandSejnowskipointexplicitlytothediscoveryofashorttermmemorydeficitforverbalmaterialsinsomesubjects.Theyalsohighlighttheabilityofvariousinterferenceeffectsbothtodissociateworkingmemoryfromlongtermmemoryinnormalsubjectsandtodissociatesubsystemsofworkingmemory(linkedwithauditory,visuospatial,andverbalmaterials)fromoneanother.Thesediscoveriesinexperimentalpsychologyprovidedbothinspirationanddirectionforneuralmodeling.Theyalsoconstituteasetoffindingsthatanyrelevantneuroscientificproposalshouldmakesenseof.

Oneventhemostexactingphilosophicalstandards,thislastconsiderationisepistemicallysignificant.Theoreticalproposalsandtheresearchtheyspawnatthehigherleveldonotmerelycontributetotheprocessofdiscoveryatthelowerlevel.Theupperlevelscienceprovidesabodyofevidenceagainstwhichthescienceatthelowerlevelcanevaluatecompetingmodels.Thisevidenceisparticularlyuseful,preciselybecauseitfrequentlyarisesindependentlyoftheformulationofthespecificlowerlevelmodelstowhoseassessmentitcontributes.Ithelpstoassuretheindependenttestabilityofthemodelsinquestion.Ithasbeenwidelyconcededthatupperleveltheoriescanplayacatalyticroleintheprocessofdiscoveryatthelowerlevel.Indeed,sometimestheconceptualresourcesandresearchtechniquesofalowerlevelsciencearebasicallyinsufficienttoenablepractitionerseventorecognizesomeofthatlevel’sfundamentalphenomenawithoutaidanddirectionfromanupperlevelscience.(Lykkenetal.(1992)constitutesaparticularlyintriguing,recentillustration.)Intheprevioussectionwealsosawhowmicroreductionisticproposalstosubordinateupperlevelexplanationstolowerlevelexplanationsriskneedlesslydownplayingvaluableresourcesfordealingwiththeoftenhugecomputationalburdenslowerleveltheoriesentail.Upperleveltheorizing(e.g.,intransmissiongenetics)contributesusefullytoeverydayscientificproblemsolving,evenafterlowerlevelresearch(e.g.inmoleculargenetics)indicatesthemicrolevelstoryisfarmorecomplicated.ScientificendeavorsatdifferentlevelsregularlydisplaywhatRobertBurton(1993)hascalleda“strategicinterdependence.”Nowwecanseethatupperleveltheorizingalsoinitiatesresearchthatcancontributetolowerleveldevelopmentspertainingdirectlytojustification.Microreductionisticproposalstosubordinateupperlevelsciencestolowerlevelscienceseitherepistemicallyormetaphysicallyriskneedlessevidentiaryimpoverishment.Thevalueofthisevidenceturnspreciselyonthefactthattheresearcharosewithinacontextofscientifictheorizingandinvestigationsufficientlyremovedandsufficientlyautonomousofthelowerlevelresearchtoinsureanhonestcheck.Thesepsychologicalfindingsdonotoccurinisolation.Theyariseinthecourseofon-goingtheorizingandresearchatthepsychologicallevel.Theirvaluetoneurosciencerestsinpartonthefactthattheyemanatefromatraditionofpsychologicaltheorizingandexperimentationthatneurosciencehasnotdominated.Thisiswhyitisworthwhileforeachlevelofanalysistomaintainameasureofindependence.AsChurchlandandSejnowskinote,experimentalpsychologyhasacenturyoffindings(andtheorizing)fromwhichneuroscientistsandneurocomputationalmodelersmaydraw(1992,p.27;seetoop.240).NothingmoreclearlyillustratesthesortofscientificopportunismexplanatorypluralismenvisionsthanoneofSejnowskiandRosenberg’spapers(1988)indefenseoftheclaimthatNETtalkplausiblymodelsoperativeprocessesinhumanlearningandcognition.(Itisafairquestionatwhatlevelofanalysisconnectionistmodelingshouldbelocated.OnthecriteriaIidentifiedinsection2,itseemstooccuratalevelbelowthatofsocialandcognitivepsychology.ChurchlandandSejnowskiclearlyregarditasaformofneurocomputationalmodeling.ItisworthnotingthatMichaelGazzanigaplacesSejnowskiandRosenberg’s(1988)inthefirsthalfofhisbook,whichconcerns“NeurobiologicConsiderationsinMemoryFunction”ratherthaninthesecondhalf,whichconcerns“PsychologicalDimensionsofMemoryFunctioninHumans.”)NETtalkisaconnectionistsystemthatconvertsEnglishtextintostringsofphonemes.(SejnowskiandRosenberg1987)Itisathreelayer,feed-forwardnetworkthatemploysthestandardback-propagationlearningalgorithm.OnanygiventrialNETtalkreceivesseveninputscorrespondingtoawindowofsevenletters(includingpunctuationorspacesbetweenwords,iftheyhappentoarise).Thedesiredoutputisthecorrectphonemeassociatedwiththefourthiteminthewindow.The

threeplacesoneithersideofthefourthitemprovidethenetworkwithinformationabouthowcontextaffectspronunciation.NETtalk’sperformanceisnothingshortofremarkable.ItcapturesmostoftheregularitiesinEnglishpronunciationandmanyoftheirregularitiesaswell.After50,000trainingtrialswithwords,itsaccuracywithphonemesapproaches95percentanditisvirtuallyperfectwithstressesandsyllableboundaries.Thecriticalquestionfornow,though,iswhatevidenceSejnowskiandRosenbergmightcitetosupporttheclaimthatNETtalkmodelsprocessesthatresemblethoseinvolvedinhumanlearningandcognition.Amodelofco-evolutionasexplanatorypluralismsuggeststhatattentiontothefindingsofexperimentalpsychologymightprovejustashelpfulhereasattentiontoresearchonneuralstructure,and,infact,notonlydoSejnowskiandRosenberglooktopsychology,theylooktooneofthosecenturyoldfindingsaboutremembering,viz.,thespacingeffect.Thespacingeffectisthefindingthatdistributedpracticewithitemsenhancestheprobabilityoftheirlongtermretentionmorethanmassedpracticedoes.Ifoccasionsforrehearsalarespacedoutovertime,theprobabilityishighthatmemoryperformancewillexceedthatfromemployingsomesmallnumberofmassedpracticesessionsofcomparabledurationattheoutset.Massedrepetitionfacilitatesmemorywhenretentionintervalsareextremelyshort.Inpracticalterms,thespacingeffectiswhycrammingforanexamisnotnearlysohelpfulasregular,dailypreparation,whereasretentionoftwonewtelephonenumberssuppliedbyDirectoryAssistancerequiresimmediate,massedrehearsal,iftheycannotbewrittendown.Inthecourseofinvestigatingthevarioushypothesespsychologistshaveofferedforexplainingthespacingeffect,researchershavedemonstrateditsrobustnessacrossahugevarietyofexperimentalsettings,materials,andtasks.Thus,SejnowskiandRosenbergsuspectthatitreflects“somethingofcentralimportanceinmemory”(1988,p.163).Consequently,itisbynomeanstrivial,ifNETtalkcanbeinducedtoexhibitthespacingeffect.Itwouldbeevenmorestriking,ifitsexhibitionoftheeffectwassimilarinformtodocumentedhumanperformance.BecauseofNETtalk’sarchitecturetheobviouscomparisoniswithstudiesofcuedrecall.SejnowskiandRosenbergchoseadesignafterGlenberg(1976).ThedesigncalledfortrainingNETtalkupinthestandardfashion,andthenpresentingitwiththecuesfromalistoftwentypairedassociateswherethosecueswerestringsofsixrandomlettersandtheirassociatedresponseswererandomlygeneratedphonemeandstressstringssixcharacterslong.(ThisinsuredthatNETtalk’sperformanceatthetestcouldnotbeafunctionofanyinformationithadacquiredaboutEnglishpronunciation.)Duringboththespacingintervalbetweentrainingopportunitiesandtheretentionintervalbeforethetest,NETtalkwaspresentedwithEnglishdistractorwordsthatwerepartofitsoriginaltrainingcorpus.Bothtrainingonthepairedassociatesanddistractorepisodesincludedfeedbackviabackpropagation.TheorderofthepresentationstoNETtalkintheexperimentwasasfollows:(1)2,10,or20presentationsofeachofthetwentypairedassociatecues;(2)aspacingintervalof0,1,4,8,20,or40distractors;(3)2,10,or20re-presentationsofeachofthetwentypairedassociatecues;(4)aretentionintervalof2,8,32,or64distractors;(5)atestofNETtalk’saccuracyincuedrecallofthetwentypairedassociates.Inshort,NETtalkdisplayedthespacingeffect:“AsignificantspacingeffectwasobservedinNETtalk:Retentionofnonwordsaftera64-itemretentionintervalwassignificantlybetterwhenpresentedatthelongerspacings(distributedpresentation)thanattheshorterspacings.Inaddition,a

significantadvantageformassedpresentationswasfoundforshort-termretentionoftheitems”(SejnowskiandRosenberg1988,p.167).Moreover,althoughdirectcomparisonwasimpossible,NETtalk’soverallresponseprofileresembledthatofGlenberg’shumansubjects.Theinterlevelinteractionherebenefitsbothcognitivepsychologyandneurocomputationalmodeling.SejnowskiandRosenbergbrieflyreviewthetwomajortheoreticalproposalsforexplainingthespacingeffectincognitivepsychology,pointingoutthatneithertheencodingvariabilityhypothesis(e.g.,Bower1972)northeprocessingefforthypothesis(e.g.,Jacoby1978)canaccountforalloftheavailabledata.Theythensuggestafurtherhypothesisfocusingontheforminwhichinformationisencodedinaconnectionistnetwork,i.e.,ontheformofthememoryrepresentation.Theyproposethattheshort-termadvantageofmassedpracticeand,particularly,thelongertermadvantageofdistributedpracticeareatleastpartiallyexplicableintermsofthedynamicsofconnectionistnets.Crucially,SejnowskiandRosenbergdonotconstruetheirhypothesisascompetingwith(letalonecorrectingoreliminating)thetwopsychologicalproposals.(Theyhave,afterall,exploredbutonesetoffindingsconcerningcuedrecall.)Instead,theyemphasizeitscompatibilitywitheach.Theyclaimcorrectlythatitoffers“adifferenttypeofexplanation”at“adifferentlevelofexplanation”(1988,p.170).Theyexplicitlydiscusswaysinwhichthenotionsof“encodingvariability”and“processingeffort”couldmapontothedynamicsofconnectionistnetworks.Thesefinergrainedaccountsoftheseprocessesintermsofanetwork’soperationssuggestbasesforelaboratingthetwohypotheses.Iftheco-evolutionofresearchininterlevelcontextsyieldstheexplanatorypluralismforwhichIhavebeenplumping,thenitisnotonlythelowerlevelthatofferstheaidandcomfort,norisitonlythehigherlevelthatreceivesit.Astheneuralmodelingofworkingmemoryillustrates,heretoopsychologicalfindingsprovidebothevidentiarysupportandstrategicguidancetolowerlevelmodelingofbrainfunctioning.SejnowskiandRosenbergremarkthat“thoseaspectsofthenetwork’sperformancethataresimilartohumanperformancearegoodcandidatesforgeneralpropertiesofnetworkmodels”(1988,p.171).Theirprojectreflectsageneralstrategyforthetestingandrefinementofneurocomputationalmodelsthatreliesontherelativeindependenceofworkinexperimentalpsychology.Featuresofparticularnetworksthatenablethemtomimicaspectsofthehumanperformancethatpsychologydocumentsthemselvesdeservemimicryinsubsequentmodelingofhumancognition.WhatisespeciallyclearaboutthecontributionofhigherlevelsinthisexampleisSejnowskiandRosenberg’sexplicitacknowledgementofjusthowfar“guidance”cango.“WhenNETtalkdeviatesfromhumanperformance,thereisgoodreasontobelievethatamoredetailedaccountofbraincircuitrymaybenecessary”(1988,pp.172).TheircommentaccordsnicelywiththeaccountofexplanatorypluralismIhavebeendeveloping.Unlikethepictureofco-evolutioninspiredbythetraditionofmicroreductionism,apragmaticallyinspiredexplanatorypluralismpermitsnoaprioripresumptionsaboutlowerlevelpriority.SejnowskiandRosenbergreadilyallowthatourpsychologicalknowledgeenjoyssufficientintegritytoforcefullyurgefurtherelaborationofanalysesofbrainsystemsformulatedatlowerlevels.16Thiswouldbenoless(nornomore)acorrectionofthelowerleveltheory(oritsontology)thanarethelowerlevel“corrections”ofupperleveltheories(andtheirontologies)theChurchlandshavesometimesbeenwonttostress.Suchdivergences,then,arenotgroundsfordismissal.Theyare,rather,opportunitiesforadvance.Theco-evolutionofsciences(notjusttheories)atcontiguouslevelsofanalysispreservesthe

pluralityofexplanatoryperspectivesthatthedistinctionsbetweenlevelsimply,becauseleavingtheseresearchtraditionstotheirowndevicesisaneffectivemeansofinsuringscientificprogress.ReferencesBechtel,W.(ed.)1986:TheNatureofScientificIntegration.IntegratingScientificDisciplines,TheHague:MartinusNijhoff.Bechtel,W.1996:Whatshouldaconnectionistphilosophyofsciencelooklike?InR.N.McCauley(ed.),TheChurchlandsandtheircritics,Oxford:BasilBlackwell.Bechtel,W.andAbrahamsen,A.A.1993:ConnectionismandtheFutureofFolkPsychology.InR.G.Burton(ed.),NaturalandArtificialMinds,Albany:SUNYPress.Bechtel,W.andRichardson,R.C.1993:DiscoveringComplexity.Princeton:PrincetonUniversityPress.Bickle,J.1992:MentalAnomalyandtheNewMind-BrainReductionism.PhilosophyofScience,59,217-230.Bower.G.H.1972:Stimulus-SamplingTheoryofEncodingVariability.InA.W.MeltonandE.Martin(eds),CodingProcessesinHumanMemory,Washington:V.H.Winston&Sons.Burton,R.G.1993:Reduction,Elimination,andStrategicInterdependence.InR.G.Burton(ed.),NaturalandArtificialMinds,Albany:SUNYPress.Causey,R.1972:UniformMicroreductions.Synthese,25,176-218.Causey,R.1977:UnityofScience.Dordrecht:Reidel.ChristensenS.M.andTurnerD.R.(eds.)1993:FolkPsychologyandthePhilosophyofMind.Hillsdale,NewJersey:LawrenceErlbaumAssociates.Churchland,P.M.1979:ScientificRealismandthePlasticityofMind.Cambridge:CambridgeUniversityPress.Churchland,P.M.1989:ANeurocomputationalPerspective:TheNatureofMindandtheStructureofScience.Cambridge:TheMITPress.Churchland,P.M.andChurchland,P.S.1990:IntertheoreticReduction:ANeuroscientist’sFieldGuide.SeminarsintheNeurosciences,2,249-256.Churchland,P.S.1986:Neurophilosophy.Cambridge:TheMITPress.Churchland,P.S.,Koch,C.,andSejnowski,T.J.1990:WhatisComputationalNeuroscience?InE.L.Schwartz(ed.),ComputationalNeuroscience,Cambridge:TheMITPress.Churchland,P.S.andSejnowski,T.J.1990:NeuralRepresentationandNeuralComputation.InW.Lycan(ed.),MindandCognition:AReader,Oxford:BasilBlackwell.

Churchland,P.S.andSejnowski,T.J.1992:TheComputationalBrain.Cambridge:TheMITPress.Dennett,D.C.1987:ThreeKindsofIntentionalPsychology.TheIntentionalStance,Cambridge:TheMITPress.Enc,B.1983:InDefenseoftheIdentityTheory.JournalofPhilosophy,80,279-298.

Feyerabend,P.K.1962:Explanation,Reduction,andEmpiricism.InH.FeiglandG.Maxwell(eds),MinnesotaStudiesinthePhilosophyofScience,VolumeIII,Minneapolis:UniversityofMinnesotaPress.Fodor,J.A.1975:TheLanguageofThought.NewYork:ThomasY.CrowellCompany.Glenberg,A.M.1976:MonotonicandNonmonotonicLagEffectsinPaired-AssociateandRecognitionMemoryParadigms.JournalofVerbalLearningandVerbalBehavior,15,1-16.Greenwood,J.D.(ed.)1991:TheFutureofFolkPsychology.NewYork:CambridgeUniversityPress.Hirst,W.andGazzaniga,M.1988:PresentandFutureofMemoryResearchandItsApplications.InM.Gazzaniga(ed.),PerspectivesinMemoryResearch,Cambridge:TheMITPress.Hooker,C.1981:"TowardsaGeneralTheoryofReduction,"Dialogue20:38-59,201-36,496-529.Jacoby,L.L.1978:OnInterpretingtheEffectsofRepetition:SolvingaProblemVersusRememberingaSolution.JournalofVerbalLearningandVerbalBehavior,17,649-667.Kuhn,T.1970:TheStructureofScientificRevolutions(2ndedition).Chicago:UniversityofChicagoPress.Laudan,L.1977:ProgressandItsProblems.Berkeley:UniversityofCaliforniaPress.Lehky,S.R.andSejnowski,T.J.1988:NetworkModelofShape-from-Shading:NeuralFunctionArisesfromBothReceptiveandProjectiveFields.Nature,333,452-454.Lykken,D.T.,McGue,M.,Tellegen,A.,andBouchard,T.J.1992:Emergenesis:GeneticTraitsThatMayNotRuninFamilies.AmericanPsychologist,47,1565-1577.McCauley,R.N.1981:HypotheticalIdentitiesandOntologicalEconomizing:CommentsonCausey’sProgramfortheUnityofScience.PhilosophyofScience,48,218-227.McCauley,R.N.1986:IntertheoreticRelationsandtheFutureofPsychology.PhilosophyofScience,53,179-199.McCauley,R.N.1987:TheRoleofCognitiveExplanationsinPsychology.Behaviorism(subsequentlyBehaviorandPhilosophy),15,27-40.McCauley,R.N.1989:PsychologyinMid-Stream.Behaviorism(subsequentlyBehaviorandPhilosophy),17,75-77.

McCauley,R.N.1993:Brainwork:AReviewofPaulChurchland’sANeurocomputationalPerspective.PhilosophicalPsychology,6,81-96.McCauley,R.N.(forthcoming):Cross-ScientificRelations:TowardanIntegratedApproachtotheStudyoftheEmotions.InB.ShoreandC.Worthman(eds),TheEmotions:Culture,Psychology,Biology.Nagel,E.1961:TheStructureofScience.NewYork:Harcourt,BraceandWorld.Neisser,U.1967:CognitivePsychology.NewYork:Appleton-Century-Crofts.Oppenheim,P.andPutnam,H.1958:UnityofScienceasaWorkingHypothesis.InH.Feigl,M.Scriven,andG.Maxwell(eds),MinnesotaStudiesinthePhilosophyofScience--VolumeII,Minneapolis:UniversityofMinnesotaPress.Richardson,R.1979:FunctionalismandReductionism.PhilosophyofScience,46,533-558.Schaffner,K.1967:ApproachestoReduction.PhilosophyofScience,34,137-147.Sejnowski,T.J.andChurchland,P.S.1989:BrainandCognition.InM.Posner(ed.),FoundationsofCognitiveScience,Cambridge:TheMITPress.Sejnowski,T.J.andRosenberg,C.R.1987:ParallelNetworksthatLearntoPronounceEnglishText.ComplexSystems,1,145-168.Sejnowski,T.J.andRosenberg,C.1988:LearningandRepresentationinConnectionistModels.InM.Gazzaniga(ed.),PerspectivesinMemoryResearch,Cambridge:TheMITPress.Thagard,P.1992:ConceptualRevolutions.Princeton:PrincetonUniversityPress.Wimsatt,W.C.1976:Reductionism,LevelsofOrganization,andtheMind-BodyProblem.InG.Globus,G.Maxwell,andI.Savodnik(eds),ConsciousnessandtheBrain,NewYork:PlenumPress.

1. The story is even more complex, since each level of analysis has both a synchronic and a diachronic moment for which separate theories have been developed. See McCauley (forthcoming). At the biological level, for example, cell biology is one of the synchronic sub-disciplines focusing on the structures within the cell whereas evolutionary biology is devoted to the study of change in forms of life over time. The Churchlands' have confined their discussions almost exclusively to synchronic examples.

2. One of the first, if not the first, is Wimsatt's (1976) classic discussion.

3. Although they concur with Churchland's judgment that the folk psychological notion of a unitary faculty of memory is probably wrong, Hirst and Gazzaniga (1988, pp. 276, 294, and 304-05) seem to adopt a far more sanguine view about the contributions of psychology (both folk and experimental) to our understanding of memory. They recognize that the fragmentation of 'memory' need not lead to its elimination. (See section 5 below.)

4. . . . and the position from which they have generally (though not unequivocally) retreated over the past few years.

5. See Churchland and Sejnowski 1990, p. 229, Churchland, Koch, and Sejnowski 1990, pp. 51 and 54, and Churchland and Sejnowski 1992, pp. 10-13.

6. Consider the discussion in Neisser (1967).

7. Interestingly, Ernest Nagel's The Structure of Science (1961), the locus classicus of traditional research on reduction, implicitly recognizes the importance of distinguishing between intralevel and interlevel contexts. Nagel consistently describes intralevel cases as involving the reduction of theories and interlevel cases as involving the reduction of sciences.

8. This is, in part, the result of the same considerations that motivate the Churchlands and Richardson's (1979) arguments that alleged reductions that conform to traditional microreductionistic standards can only be domain specific.

9. –or in neuropsychology, as Churchland and Sejnowski's (1992, p. 282) discussion of the role of the hippocampus in short term memory illustrates. See P.S. Churchland 1986, p. 361.

10. An interesting illustration arises in Churchland and Sejnowski's discussion of the major levels of organization in the nervous system (1992, pp. 10-11). Their diagram of the relevant levels tops out at the central nervous system with no mention of psychology. The obvious defense is to note that the diagram addresses anatomical structures of the nervous system only. Fair enough. What is telling, though, is a footnote (1992, p. 11, footnote 5) to this discussion. Churchland and Sejnowski concede that a more comprehensive account would include a social level above the central nervous system. At least for the purposes of this discussion, they seem not even to countenance the possibility that cognitive research may capture organizational structure of explanatory significance not immediately reducible to the neurophysiological. (See too Sejnowski and Churchland 1989, p. 343.)

A meta-level comment: the physicalist holds that metaphysical manifestness (which, remember, is physical manifestness for the physicalist) constrains what will count as satisfactory explanation, whereas the pragmatist proposes that explanatory success should constrain metaphysical commitment. If that diagnosis is correct, the on-going negotiation in the Churchlands' work I described in section 3 is, at its root, one about competing norms.

11. I should emphasize that I am speaking of the elimination of folk psychology as an explanatory construct within scientific psychology. The elimination of the principles of folk physics centuries ago in physics has had little effect on its persistence among the folk.

12. The illustrations the Churchlands (1990) offer in support of their “overview of the general nature of intertheoretic reduction” (p. 249) proceed in the following order:

(1) the reduction of Kepler's laws to Newton's (intralevel);

(2) the reduction of the ideal gas law to the kinetic theory--emphasizing (p. 250, some emphasis added) that “this reduction involved identifying a familiar phenomenal property of common objects with a highly unfamiliar micro-physical property” (interlevel);

(3) the reduction of classical (valence) chemistry by atomic and sub-atomic (quantum) physics (interlevel);

(4) the reduction of Newtonian mechanics to the mechanics of Special Relativity (intralevel);

(5) the elimination of phlogiston by Lavoisier's oxygen theory of combustion (intralevel).

13. But just as progress in tracing the relevant biological systems preserved the vitality of organisms without vitalism, so too is progress at tracing the relevant psychological systems slowly revealing how we can preserve the cleverness and wondrous experiences of intelligent creatures without dualism. The interlevel influences of neuroscience will no more co-opt or eliminate psychological theorizing than the interlevel influences of chemistry co-opted or eliminated physiological theorizing.

14. As noted near the end of section III, the Churchlands more often seem to endorse an account of co-evolution resembling co-evolutionP. In Churchland and Sejnowski 1990 (p. 250) and 1992 (p. 240), they not only advocate a form of explanatory pluralism, but they explicitly include the psychological sciences.

15. Conceding that it will not involve a single model nor direct explanations of higher levels in terms of events at the molecular level, Churchland and Sejnowski, nonetheless, aspire to a “unified account” of the nervous system, where “the integration [will] consist of a chain of theories and models that links adjacent levels” (Sejnowski and Churchland 1989, p. 343).

16. If neurocomputational modeling of networks constitutes a higher level of analysis than does the study of particular neurons (and it certainly seems to on Churchland and Sejnowski's view – 1992, p. 11), then Churchland and Sejnowski's (1992, pp. 183-188) take on recordings of single cells' response profiles in the visual cortex is an illustration of just the sort of circumstances that the Sejnowski and Rosenberg citation allows for--one in which higher level research impels a reevaluation of lower level doctrines.

Churchland and Sejnowski (following Lehky and Sejnowski 1988) argue that neurocomputational research on the visual system's ability to extract shapes exclusively from information about shading reveals that the conventional interpretation of the function of receptive fields of neurons in the visual cortex may well be wrong. That interpretation, which arose from single cell studies, holds that these neurons function as edge and bar detectors. Churchland and Sejnowski maintain that this interpretation ignores the cells' projective fields. Hidden units in Lehky and Sejnowski's model developed receptive fields with similar response profiles, however these orientations were the result of training the network on the shape from shading task. “In a trained-up network, the hidden units represent an intermediate transformation for a computational task quite different from the one that has been customarily ascribed . . . they

are used to determine the shape from the shading, not to detect boundaries” (Churchland and Sejnowski 1992, pp. 185-186).

Explanatory Pluralism And The Co-Evolution Of Theories In Science …mechanism.ucsd.edu/~bill/teaching/w17/phil151/mccauley... · 2017-01-12 · Explanatory Pluralism And The Co-Evolution

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