Hyman 1992_The Causal Theory of Perception

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The Causal Theory of PerceptionAuthor(s): John HymanSource: The Philosophical Quarterly, Vol. 42, No. 168 (Jul., 1992), pp. 277-296Published by: Wiley for The Philosophical Quarterly

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ThePhilosophicaluarterlyol. 2No. 168 July 992ISSN 0031 8094 2.00

The Philosophical Quarterly

THE CAUSAL THEORY OF PERCEPTION

BYJOHN YMAN

I

The causal theoryof perceptionis an exercise in what Sir PeterStrawson famously called descriptive metaphysics.' Descriptivemetaphysicsaims 'to lay bare the most general featuresof our

conceptualstructure';2nd the causal theory urports o identifyneof these

features,ne element n the massive central core ofhuman

thinkingwhich has no history'.3t says that the conceptofa causalconnection,which unquestionablyhas a fundamentalplace in our

thinkingbout thenaturalworldwe inhabitand inourthinkingboutourownpowerto effect rprevent hanges nit, salso implicit n the

ordinarynotionofperceiving'.4The theory roposes hat t spartofthemeaningof, or xample,the

statementDavid saw Bath-Sheba washingherself'thatBath-Sheba,the woman that David saw, was causally responsiblefor a sensoryexperiencewhichwould be correctly eported y sayingIt appeared tohimustas ifhe sawa womanwashingherself', r It seemed tohimustas ifhe saw a womanwashingherself'. n general, perceptualverb sused to say that a person had, is having or will have a sensoryexperiencewhichwas or will be caused bywhatever t s an experienceof. hope toshow thatthearguments fferedn supportof thetheory

'I am indebted to Hanjo Glock, Peter Hacker and Stephen Mulhall for theircomments n earlierdrafts,nd toSir PeterStrawsonformanyconversationsbout thecausal theory.

2 P. F. Strawson, ndividualsLondon: Methuen, 1959), 9.3 Ibid., 10.4 H. P. Grice, The Causal TheoryofPerception',ProceedingsftheAristotelianociety,

Suppl. Vol. 35 (1961), 143; cf. Strawson, Causation in Perception', n Freedom ndResentmentnd Other ssays London: Methuen,1974), 72.







278 JOHN HYMAN

are inadequate, and that the theory tself ncorporatesa defective

psychologynd a defective pistemology.There is no denyingthat we could not hear and see the sounds and

sightswe do if thenoisyand colourful bjectswe perceivedid not actcausally on our sense organs. However, that observation concedes

nothing o the causal theory; orwhatan advocate of thetheoryneedsto show s, first,hat thenoisy nd colourful hingswe hear and seedonotmerely ct causallyon oursenseorgans,butbydoingso cause us tohave sensory experienceswhich are correctlyreported by sayingsomething ike It seems to me just as if. . . '; and second, that theexistenceof this causal chain is not a hard-wonpiece of scientific

knowledge bout ourphysicalnature,butpartof'theordinarynotionofperceiving'.

II

There are twoprincipalargumentswhich are thought o supportthe

theory. he first, hich s due toGrice, s this: merecorrespondencebetweenwhata persontakeshimself osee,and what s therebeforehis

eyes,does not

byitself stablishthat he sees what he thinkshe sees,

because this orrespondencemaybe a coincidence;or tmayhave beencontrived, ather hanresulting rom he normal exerciseofhisvisual

faculty.5 rice's example ofa contrivance s a case where someone ismade to have an hallucination whichcorresponds xactlywith what

happensto lie infront fhiseyes;hisexampleofa coincidence sa casewhere omeonesees a column n a mirrorwhich, s ithappens,hidesanidentical column fromhissight:

Suppose that t ooks toX as if here sa clock on the helf;whatmore srequiredfort to be true osaythatXsees a clockon theshelf?There must,one might ay, actually be a clockon theshelfwhich s in X's field fview,beforeX's eyes.But thisdoes

5 This argument,n the versionwhichplayson the dea ofa coincidence, s very iketheargumentDavidson offersn supportofhis causal theory f action.What,Davidsonasks, s thedifference etweenvisiting ourgrandmothernd hopingto be included n herwill, nd visiting ourgrandmother ecause ouhope tobe included n herwill? n thefirst

case, your pecuniarymbition

gives youagood

reason to visither,

butthe factthatyouhave this mbition nd act in a waywhich slikely ofurthert smerely oincidental. n

the secondcase, it s not.But whatcould thespecial relationship etween ct and reasonwhenyouactfor reasonbe, excepta causal relation?Failinga satisfactorylternative',writes avidson, thebest rgument for he ausal theory]s that talonepromises ogivean account ofthe"mysteriousonnection"between reasons nd actions' (D. Davidson,'Actions,Reasons,and Causes', inEssays nActionsndEventsOxford:OxfordUniversityPress,1980), 11).







THE CAUSAL THEORY OF PERCEPTION 279

notseem tobe enough.Forit s ogically onceivable thatthereshouldbe somemethodbywhichan expert ould make it ooktoX as iftherewerea clock on theshelf n occasionswhenthe

shelfwas empty:theremightbe someapparatus bywhich X'scortex could be suitably stimulated, or some techniqueanalogous topost-hypnoticuggestion.f suchtreatmentwere

applied toX on an occasionwhen there ctuallywas a clock onthe shelf,and if X's impressionswere found to continue

unchangedwhen the clock was removedor tsposition ltered,then thinkwe shouldbe inclinedtosaythatX did not see theclockwhich was beforehiseyes, ust because we shouldregard

theclockas playingnopart n theorigination fhis mpression.Or, to leave the realmoffantasy,tmightbe that t looked tome as iftherewerea certain ortofpillar n a certaindirectionat a certaindistance, nd theremight ctuallybe sucha pillarin that place; but if,unknownto me, therewere a mirror

interposed between me and the pillar, which reflecteda

numerically ifferenthough imilarpillar, t would certainlybe incorrect osaythat saw thefirst illar,and correct osaythat saw thesecond;and itis extremely empting oexplainthis inguistic actbysayingthatthefirst illarwas, and thesecondwas not,causallyirrelevant otheway thingsooked tome.6

Examples of the same kind recur throughout he literature.For

example, Pears tellsthefollowing tory:

P. isa travellernthedesert, nd hehallucinatedan oasiswith

his eyes closed, so there can be no doubt that [his visualexperience]was not caused by anythingbeyond his eyelids.However,there sa real oasis ... infront fhimand [hisvisual

experience] matches it perfectly eatureby feature. But P.cannot be seeing [the oasis] because though the match is

perfect,tis entirely oincidental.7

Neither the storiesof coincidences nor the storiesof contrivances

actuallyshowwhat they re meant to,forthere s no reasonwhyweshould regard them as stories about differentways of causingimpressions,whenwhat they re obviouslyabout is different aysof

6Grice, Causal Theory', 142.D. F. Pears, The Causal TheoryofPerception', ynthese3 (1976).







280 JOHN HYMAN

causallypreventing omeonefrom eeing something byan obstacle,byan apparatus,etc. In the case ofthepillars,Grice can see thesecond

pillarand cannot see the first ecause the secondpillar svisible in the

mirror) romwherehe isstanding,whereas thefirstshiddenfrom iew(bythemirror, s ithappens). It would indeedbe incorrect osaythathe saw the first illar- because he was preventedfrom eeing tbyanobstacle.The case involving heapparatus issimilar.As Gricesays,weshouldbe inclined tosaythatXdid not see theclock;but thereasonforthis s thatX's failure o react when theclock was moved showsthatthe

apparatus preventedX from eeingwhat was beforehiseyes.Grice's argument is meant to demonstratethat the concept of

perception contains within itself the idea of a causal connectionbetweentheenvironment nd ourexperience.However,theargumentonlysucceeds n illustratingheplatitudethat f see something, henI am freefromwhatever causal constraintswould preventme from

seeing it. And neither the fact that I can be causally constrainedfromeeing omething bya blindfold, ya mirror, ymyowneyelidsorbya drug- northe factthat f seesomething, hen am free rom

anysuchconstraint ntailsthatwhen do seesomething, hefact hatsee it is

causallyexplainedbythefactthat tis there.

III

The secondargumentwhich s thought osupportthe causal theorysofa differentort.The argumentdoes notturn n a storynwhich the

wrong sort of cause allegedly precludes an experience frombeingclassified s a perception; r a storynwhich the cause of n experiencedecides what has been perceived. It is propounded by Strawson as

follows:

We thinkofperceptionas a way . . . of informingurselvesabout the worldof ndependently xisting hings:we assume,that is to say, the general reliabilityof our perceptualexperiences; nd that ssumptions the ameas theassumptionofa generalcausal dependence of our perceptual experienceson the ndependently xisting hingswe take them tobe of.8

The idea is a simpleone. It can be expressedntheform f question.How can sightand hearingbe cognitivefaculties,waysofcomingto

8 P. F. Strawson, Perceptionand itsObjects', in G. F. Macdonald (ed.), Perceptionand dentityLondon: Macmillan, 1979), 51.








know things bout our surroundings, nless our visual and acoustic

experiences re somehowresponsive o oursurroundings;nd how canour experiences be responsive to our surroundingsunless their

character s generallydetermined i.e. caused - by thethingswhichsurround s? The idea of causal connectionbetweentheenvironmentand our experience is implicit in the very concept of perception,because we think fthe senses s cognitivefaculties.

The argument splausible;but t sspecious. t is true hatwethink f

perception s a wayof nformingurselves.But thisdoes not mply hat'we assume ... thegeneralreliability f our perceptual experiences',unlesswe also assume thattheword perception'refersoan experience

ofthekindenvisagedby the causal theory. fwe assume thatthefivesenses are capacities forhaving experiencesof this kind, then the

thoughtthatperception s a way ofinformingurselves s bound toseemequivalentto thethought hat theseexperiences re normallyreliableguidetotheperceptible nvironment. ut fwe assumenothingof the kind, and instead construe our perceptual experiences' as

meaning ourseeingthis nd hearing hat',then heremarkwe assume... thegeneralreliability fourperceptual experiences'willno longerseemto follow rom heprecedingremark,We think fperception s a

way... of nformingurselves'. ndeed, on this eading, heremark weassume . . . the general reliabilityof our perceptual experiences'becomesfalse.I seethatp'entailsp;hence we do notassumethegeneralreliability f our perceptual experiences,on thisreading,any morethanwe assume thegeneralreliability f modusonens.

Strawson aims to demonstrate hatthevery dea that the sensesare

cognitivefaculties lready contains within tself he idea ofa causalconnection between the environment nd our experience. But, like

Grice,he takes t forgrantedthatany exerciseof thefaculty fsight,hearing, tc. nvolves hese wo ngredients:n object ntheperceptibleenvironment nd a psychological pisodewhich s reportedby saying'It seems to mejust as if... ', 'It sensibly eems to me as if. . .' or

something imilar.His argument eaves us inno doubt that fthese retheright ngredients, hen there s onlyone way ofcombiningthemwhich makesitclearwhytheexperience s normally reliableguide.But the argument is fruitless nless it can be shown that these

ingredientsre theright nes.

IV

Whathas persuaded philosophers hatour five enses re capacitiesfor

having experiences which are not reported simply by using a







282 JOHN HYMAN

perceptualverb,butbyprefacingtwiththephrase It seemstomejustas if... '? The answer, s we shallsee,has to do withthephenomenaof

perceptual llusion and hallucination;but an important ualification

mustbe stated at once.The various arguments which are known collectively as the

Argument romllusion weretraditionally sed toprovethe existenceof ense-data, nd to raisetheepistemological roblems hat ense-data

carry n theirwake;whereas the chief easonwhyGriceand Strawsonsucceeded in restoring he causal theory'sreputationwas that theydetached it from henotionthat the immediateobjectsofperceptualawareness are psychologicalentitiesof some sort (Cartesian 'ideas',

Humean 'impressions',Kantian 'Vorstellungen', sense-data', qualia'or whatever) and thusprotected t against the charge that it fosters

scepticism. he Argument rom llusion was notso muchrepudiated s

circumnavigated by Grice. But Strawson explicitlydissociated thecausal theory rom ts conclusion:

we take ourselves to be immediately ware ofreal, enduringphysical hingsnspace, things ndowedwithvisual and tactile

properties... The immediacywhichcommon ense ttributes

toperceptualawareness s in no way inconsistent.. with thecausal dependence of [visual experience] on [the thingswe

perceive].9

Griceand Strawson showed thata causal theory fperceptiondoesnot need to postulate a private and impalpable picture gallery to

explain either vision or hallucination.But even if we escape to thisextent from the grip exerted by the ArgumentfromIllusion, the

phenomenaofperceptual llusion nd hallucination an still eem fit oplaya crucial role nthephilosophical nalysis fperception.Their rolein the causal theory s to make it appear plausible that perceivinginvolves n experiencewhich s reportedbyusingthephrase It seemstome ust as if. '.

Strawson ntroduces hephraseas follows. upposewe asksomebodyfor description r a 'strict ccount' of his current isual experience'.The requestwould onlybe met,Strawsonclaims,by an account ofa

particularsort: an account which confines tself

trictlywithinthe

limits f thesubjectiveepisode,an accountwhichwould remain trueeven ifhe had seen nothingofwhat he claimed to see, even ifhe hadbeen subjectto total llusion'.'0

9 Strawson,Perception nd itsObjects', 53.,0 Ibid., 43.








The requestfor description f omeone's current isualexperience'is a strange ne, although tmightbe made in an effort o monitorhis

gradually failingeyesight;and the question 'How is it with you,

visually, t themoment?',"whichStrawsonsuggests ould be used tomake therequest, sbarely ntelligible. ut does thismatter?The remark hat turn fphrase oundspeculiardoesnot amount to

a philosophical rgument.But itmaybe a clue. For we are examiningan attemptto elucidate 'the ordinarynotion of perceiving';and adistortion fan ordinarynotionis bound to betray tselfn turnsofphrasewhich strikethe ear - except,perhaps, an ear calloused byjargon - as strange nd clumsy.1

If we followtheclue, we shall soon encounter a more substantialissue.The philosophicalmotive or hese dd turns fphrase sperfectlyevident nd clearly tated: as Strawson ays,therequest s intendedtoconfine ttention strictlywithinthelimitsofthesubjective episode'.The substantial ssue swhether hismanoeuvre sobjectionable n anyway. Does itdistort heordinarynotionofperceiving?

The answerdependson whether tis possibleto conceptually kim

off'"3 purelypsychic ventfrom heexercise f perceptualpower, nevent which can also occur when a person perceives nothingwhatsoever. fthis spossible,then, s Strawson ays, 'strict ccount'of omeone'sexperience f eeing omethingwould remaintrue ven ifit transpired hathe had been subjectto total illusion';and it is clearthat sentence ftheformIt seems to me (orhim) ust as if... ' wouldbe tailor-made ofurnishuchan account.However, f t snotpossible,then thecausal theory s unsustainable.Cause and effectre distinctexistences: fX is thecause ofY then t slogicallypossibleforY toexistwithoutX and vice versa.Hence, thesortofexperienceenvisaged by

thecausal theorymustbe one which t ispossibleto have even thoughnothingwhichcorresponds o it is within ight rwithin arshot.

Is it not implausiblethat theexperienceofhearingsomething ndthe xperience f eeing omethingreexperiences ne can havedespitefailing o hearorseeanythingt all - even ntotaldarkness nd perfectsilence?One cannot have the experience of a university ducationwithouthavinga universityducation or- a verydifferentase - havetheexperienceoftoothachewithouthavingtoothache.Whyshouldit

be thoughtpossible to have the experience - or, if either phrase

" Ibid., 43."2Strawsonhimselfs wellaware thattheseturns fphraseare odd, and payscriticalattention o the fact.

13 The phrase sJohnW. Cook's. See his Human Beings', n P. Winch (ed.), Studiesnthe hilosophyf WittgensteinLondon: Routledgeand Kegan Paul, 1969), 127.







284 JOHN HYMAN

commends itself, the 'sensible experience' or 'slice of sensible

experience14 ofseeingor hearingsomethingwithout ctuallydoingso? The words 'the experience of' are not exactly pleonastic: for

example, theymay be intendedto signal thespeaker's nterestn thelasting mpression hatdoingorsufferingrwitnessingomething anmake,the asting nfluencet can have,the education t can provideorthe uthorityt can confer.However,one cannothavetheexperience f

performing Chopin Ballade or climbingthe Matterhorn without

performingheBallade or climbingthe Matterhorn.At best,one can

imagine havingtheexperience. Some people can and somecannot.)But imagininghavingan experience s not anotherway ofhavingit,

anymore than magining limbing heMatterhornsanother and lessstrenuous) way of gettingto the summit.Why should seeing themountain orhearingthepiece performed e anydifferent?

No reason s statedexplicitly, ut it s obvious what Strawsonhas inmind: namely,the thoughtthata perceptionand thecorresponding'total illusion' are indistinguishable rom hesubject'spointofview.

Surely we want tosay- this amiliar nd indisputablefactmplies hatthepsychological pisodeswhichoccurwhen I hear or see somethingand those whichoccurwhen I am 'subject to total illusion'resemble

each otherperfectly:1'whether am hearingthepeal ofchurchbellsor'hearing'the church bells ofmynativeEnglishvillagewhiletravellingin thedeserts f the Near East,'6the same It seemsto me ust as if. ..sentence s true,because thesame purely ubjective pisodeoccurs.

V

It is undeniable that a perception nd thecorrespondingllusion are

indistinguishablerom hesubject's pointofview;'7but t snot an easymatter o decidehowthispropositionhould be interpretedndwhat t

implies.Does it implythatseeinga roseand hearingthepeal of bells

14Strawson,Perception nd itsObjects', 43.'5 Grice refersxplicitly o a genericresemblance, ignalizedby the use of theword

"look", which differentiates isual fromnon-visual sense-experience'.Grice, 'SomeRemarks bout theSenses', nR.J. Butler ed.), Analyticalhilosophy:irst eriesOxford:BasilBlackwell,1962), 152.AndJohnMcDowell, who ssceptical bout the ausal theory,is nevertheless

willingto allow 'what is

givento

experiencen thetwosortsof case [sc.

perception nd illusion]to be the ame in o aras it s an appearance thatthings re thusand so' (McDowell, 'Criteria,Defeasibility, nd Knowledge', ProceedingsftheBritishAcademy,ol. 68 (1982), 475).16The exampleisfromKinglake'sEothen, hich squoted byStrawson,Causation in

Perception',77-8.1/However, the nominalization a perception'needs to be treatedwith care. See

P. M. S. Hacker,AppearancendRealityOxford:Basil Blackwell,1987),67.







THECAUSALTHEORY OF PERCEPTION 285

involve the occurrence of subjectiveepisodes which can also occurwhena person ssubjectto total llusion?'8 onsider an example.

Suppose thatA, gazing into thenight ky, ees a shooting tar and

points t out tohiscompanionB, whoactuallymisses t,butfancies,nhisexcitement, hat he sees it too. B's experiencemaynot have been

sufficientlylarmingto be called an hallucination,but neverthelesstseemedtohim ust as ifhe saw exactlywhat,as a matter ffact,A didsee.

The relationshipbetweenB's illusion and A's perceptioncan be

explained ntwo tages.First,what fancied hathe saw and whatAsaware one and the same. Of course,thisdoes not mean one and the same

experience.B did notfancy hathesaw an experience, nd A did not seeone.) It means that thequestion What did A see?' and thequestion'What did B seem to see?' have one and the same answer:A shootingstar'.

We can expressthis factby sayingthatB's illusioncorrespondedexactlywithA's perception.But this,by itself, oes not implythatAand B enjoyed similar subjective episodes, any more than a

correspondence etweenC's suspicion nd D's denial (ifC suspects hat

pbutD denies that

p) impliesthatC's

suspicionnd D's denial involve

the occurrence of similar subjective episodes. The correspondencealone cannot show that both answers report the occurrence of a

subjective episode, in the required sense of the phrase 'subjectiveepisode'.

Now for the second stage. Consider the proposition that B's

experience nd A's are indistinguishable. ere, ofcourse,theanalogywithC's suspicion nd D's denial breaksdown,for here snoreason todescribethe atter s indistinguishable toC, toD, or toanybodyelse.

And here,one might uppose,is the evidence that theexerciseofourperceptual faculties nvolves the occurrence of subjective episodeswhich can also occurwhena person ssubjectto total llusion.

Statedwithout ualification, heproposition hatB's experience ndA's are indistinguishables certainly alse.Anyonepresentmayhavebeen able to tellthatB's imaginationhad gotthebetter fhim.Even Bhimselfmay have realized, and so even B may have been able to

distinguishbetweenhis own experienceand A's. None the less,one

mightwant to insist hat therewas nothing ntrinsicoB's experiencewhichmighthave enabled himto know thathe was notseeingwhathe

thoughhe saw. He mighthave surmised hatwith bad eyesight nd a

18Paul Snowdon ('Perception,Vision and Causation', Proceedingsf theAristotelianSocietyol. 81 (1980-1) andJohnMcDowell ('Criteria')havealso argued, s I shallarguebya differentoute, hat tdoes not (butsee n. 15,above).







286 JOHN HYMAN

livelymagination heodds werethathe had beencarried way.But his

experiencedid not tself arrythestampofmere llusion.Ifsomething fthis ort swhatismeantbytheproposition hatB's

illusion and A's perceptionare indistinguishablefromthe subject'spointofview', can we infer hat B had the same experience s A? Theshort nswer s thatwe cannot: we can onlyinfer hatpresumablyi.e.unlesshesurmised tc.) B believedhathe had the ameexperience s A.We can stateas a generalprinciplethat thecorresponding erceptualbelief in thiscase, B's beliefthat he saw theshooting tar) typicallyaccompanies an illusion. But the relation between illusion and

perceptionembodied in thisprincipleis a non-symmetric oxastic

relation: it is not the symmetric on-doxastic relation- the perfectresemblancebetweentwomentalepisodes- which the causal theoryrequires.

It might eemas ifthestory s finished, ut it is not,forthere s aforcefulemptation o ask a furtheruestionhere:namely,why o we

typicallymistake an illusion fora perception?This temptation sirresistiblefwe assume what we areseeking oprove that t spossibleto hive off purely ubjective pisodefrom heexercise f perceptualpower, and hence that the tendencyto mistake an illusion for a

perception s a tendency omistakeone kindofsubjectiveepisodeforanother. And the question only has one answer: these subjectiveepisodesresemble ach other.

However,thetemptation oaskwhywe typicallymistake n illusionfor perception hould be resisted.To understandwhy,we need tothink about the word 'typically'. If the word were being used

statistically ere i.e.,if t meantthat n illusion saccompaniedbythe

corresponding elief n themajorityfcases then we would ofcourse

want to accountfor his orrelation. ut nfact heword typically' oesnot referto a correlation between illusion and belief,which needs

explaining.On thecontrary,tsignifieshat n explanation srequiredif,and only if,an illusionis not ccompanied by the correspondingbelief. orexample, f travellernthedeserthas an hallucination, nditseems tohimust as ifhe can see an oasis,but he doesnot believethathe sseeing n oasis,thiswillneedexplaining.How did heknowthathissensesweredeceivinghim?The answermaybe thathe knewtherewere

no oases thereabouts; or perhaps he knew that travellers n hiscircumstances endtohave hallucinations; rperhapshesimplyhad ahunch. But ifthe travellerdoesbelieve that he is seeing an oasis, no

explanation scalled for.The question, Why do we typicallymistake an illusion for a

perception?nvitesus to suppose that llusionand perception nvolve








theoccurrenceofsimilarsubjectiveepisodes. But the question itself

presupposes distorted iewof therelationshipbetween llusion andbelief. It must therefore e rejected, ust as we would reject the

question,whydo animalstypicallywant to avoiddiscomfortnd pain?,forhere ina similarway- theword typically' ignalsthefact hatthedesire to avoid discomfort nd pain needs no explaining. On the

contrary, hatneedsexplaining swhensomeonehas nodesiretoavoiddiscomfortrpain, orpositivelyeeks t.

The proposition that a perception and the correspondinghallucination re indistinguishablerom he ubject'spointofviewusesthe vocabulary of resemblance to signifya different although

connected)relationship: hedoxastic inkwhichweexpressedby ayingthat the correspondingperceptual belieftypically accompanies anillusion.19 ence, the fact that a perceptionand the correspondinghallucination reindistinguishablerom he ubject'spointofview doesnotafter ll providetheuncontentious remise hat thecausal theoryneeds,because itdoesnot mply hattheexperience f actually) seeingorhearing omethingsone thatcan also occur without nything eingseenorheard at all. We must hereforeonclude thatthephenomenaof

perceptualillusion and hallucination cannot play the role in whichthey re cast bythecausal theory.

VI

In the ast section examined theproposition hat perception nd the

correspondingllusion re indistinguishablerom hesubject'spointofview, and I argued that it does not imply that the psychologicalepisodeswhich occur when I hear or see something nd those which

occurwhenI am subjecttothecorrespondingtotal illusion'resembleeach otherperfectly.n this ection, shall argue that thevery dea ofsucha resemblance s incoherent.

Ifone thing s said toresemble nother,we are entitled o askwhatsort fresemblances ntended.Arethey imilar nappearance,do theyhave the same habits,do theymake the same noises?For example,we

mightexplain how two rosesare alike by specifyinghe perceptualmodalityof theirresemblance.Perhaps they ook alike and perhaps

"9This is a common featureof our use of language. There are many bundles ofassociated words and phrases which are used in a particlalar ontext without theircustomaryignificance. orexample,thevariousverbs fpossession hatwe use to ascribeexperience o notsignify kindofownership. can trade glanceat your igarette ardsfor glance at mine,but I cannot trademy glance foryours, ven thoughwe speak ofhavingand takingglances.







288 JOHN HYMAN

theysmell alike. By implication,of course,we identify heway theresemblance is discerned (looking, sniffing) nd the opportunityconditionsfordiscerning t (adequate illumination,nothingwith a

strong mell close by).On the other hand, ifone physical sensationis said to resembleanother there s no questionofspecifyingheperceptual modalityoftheirresemblance,forsensationsare not perceived. If an object (orevent) is perceived then it can exist (or occur) unperceived,or be

misperceived. ut there sno suchthing s an itchwhichwas notfelt ra giddyfeelingwhichnobodywas aware of;and although t spossibleto be mistaken bout thecause of sensation nehas,onecannotfalsely

believe thatone is sore or itchyor in pain and one cannotmistaketoothachefor feeling f nausea.Since sensations are not perceived,the many distinctive ualities

thatthey an have are notperceptible ualities,and it sconvenient ouse the termphenomenal' to refer o their ualitiescollectively.

There are variousways in which sensationscan be described.To

beginwith,wepossess small numberofnouns,for xample pain' and'itch', which are defined n termsof the characteristicbehavioural

expression f the sensationswhichtheyrefer o. But for he mostpart,sensations re describedbycausal analogy (e.g. as burning, tinging,stabbing,throbbingor pulsating) - for the most part, because the

phrase It feels s if'can be used togeneratedescriptionsfthiskind dlibitume.g. It feels s ifmy hroathas beenrubbedwith andpaper', Itfelt s ifmycheeks wereon fire', tc.). Note also that thepart of the

bodywhich tchesor tinglesmay itchor tinglemore or less ntensely;and that, nadditionto theirphenomenal qualities,sensationsmaybemoreor lesspleasantorunpleasant.

If the experience of (actually) seeing a shooting star and thecorrespondingllusionresemble ach other, his annotmean thattheyare visiblyimilar. For theonlyvisibleresemblance n theoffings theresemblancebetweenA's appearance - thatis, his appearance to anonlooker when he saw theshooting tar and B's appearance when hefanciedthathe saw it. And similarly,n audible resemblancebetweenthe experience of hearing the peal of church bells and Kinglake'shallucination ould onlybe a resemblancebetweenthenoisestypically

made by English villagerson Sunday mornings nd the noise thatKinglakemade as he trudged cross the desert ands.

But there s no question of a phenomenalesemblanceeither. Two

physicalsensations re alike, regardless fwhat caused them, ftheyshare the same phenomenal qualities; but neitherthe experienceof

hearing the church bells nor the correspondinghallucination is a








physical sensation and neither would normally be described as

burning, marting,tinging, aggingor tingling.20he phrase feels sifit was caused by gritunder an eyelid' describes the phenomenal

quality of a sensation;but thephrase sounds as if twas caused bychurch bells' describesa sound that is heard, not the experienceof

hearing it. The visual and acoustic experiences which have

phenomenal properties re the sensations aused by dazzling lightor

deafeningnoise; but far frombeing essential to the exercise of our

perceptual faculties, these sensations impede their normal

functioning.2'Our normalvisualand acousticexperiences re,of ourse, apable of

beingdescribed n a variety fways.The experienceofseeinga rosemay be disappointing ifthe rose has mildew), delightfulif t is pinkand blowzy nd infullbloom),sentimentalif tremindsme of tender

moment)orhumiliatingif, s usual,myneighbour'sgarden putsmineinthe hade). Andan hallucinationmaybe terrifying,isorientatingr

entertaining. uta perception nd thecorrespondingllusionneednotshareanyadventitious haracteristics f this ort.

If the psychological episodes which occur when I hear or see

something and those which occur when I am subject to the

correspondingtotal illusion' resemble each otherperfectly,hen itmustbepossibletosaywhat kindofresemblance his s.Hence, ifwefailtodo this,we are bound to conclude that the dea ofa resemblance saconfusedone. We can, ifwe like, persist n saying thatB's illusionresembledA's perception and resembled it perfectly, ut thiswill

simply be another way of stating- in the guise of a potentiallymisleading terminology that B's illusion correspondedwith A's

perception; hat s,that thequestionsWhat did A see?' and 'What did

B fancy hat he saw?' have thesame answer.Once again, we are forced to conclude that an illusionis not an

experiencewhich perfectly esemblesthe correspondingperceptualexperience. But we should not inferfrom this that perceptionandillusionare dissimilarubjectiveepisodes,forwhatever abel we attachtothem, hey annot both be called 'subjective pisodes' none and thesame sense of the phrase. The same sentence answers the questions'What did A see?' and 'What did B fancy hat he saw?'; but itis being

20As it happens, Kinglake did maintain that his hallucination occurredbecause anumberof causes 'had rendered his hearing organs] liable to tingleunder thepassingtouch of some merememory'. Quoted by Strawson, Causation in Perception'.)Thissounds like a figurative ingle. Was it suggestedby thesimilar-soundingtinkle'?)Buteven fhis ears iterally ingled nd thetinglewas connectedwiththe fact hathe heard'the churchbells,this tilldoes not amount to a tingling allucination!

21 See Hacker,AppearancendReality,4-5.







290 JOHN HYMAN

used in twoquite different ays. It does not refern both cases to a

subjective pisode: nthefirstase ('What didAsee?'; A shooting tar')itreferso a visible hing, meteor ntering he arth's tmosphere, nd

asserts relationbetweenAand this isible hing;but nthe econd case(whether rnotB knows t orsuspects t) itrefers onothingwhatsoeverand doesnotassert relation f nykind: tsayswhatB fancied hathesaw. (It does not even refer oa psychological pisode, although B hadthe illusion of seeing a shooting star' refers o B and says that a

psychological pisode tookplace.)Pears'sremark, hat n hallucination an 'match[an oasis] perfectly

featurebyfeature',was quoted in section I. We can nowsee that this

remark is not an ellipsis which, if spelt out, would read 'anhallucination an match theexperience aused byan oasisperfectly':tidentifies he relata explicitly.And the word 'match', like the word

'corresponds', oes notsignifynykindofresemblance. How could it?How could an hallucinationresemble n oasis?) It signifieshe use ofacommonform fwords servingnone case to describe visiblefeatureofthe nvironmentlush,wet, prouting alm trees) nd intheother, o

report pseudo isual experience.

VII

The causal theory mpliesthat the five enses are capacities to enjoy'subjective pisodes'ofvarious kinds episodeswhichnormally o, but

occasionally do not, provide us with a reliable basis forbelievingsomething bout theperceptible nvironment.fwe rejectthetheory,must we conclude that the five senses are not capacities forhavingperceptualexperiences?-No. eeinga rose and hearingthepeal of bells

are evidently xperiences, n one sense (or two) of thisversatileword.But not in the sense that thecausal theory equires,fortheyare not

purelymentalepisodeswhich can be conceptually kimmed ff he ifeof a sentient reature. And the fact that a pseudovisual or acoustic

experience s as good an example as we shall findofa purelymental

episodedoes notprovethecontrary.The doctrine that the exercise ofany psychologicalfaculty be it

thought r feeling, maginationorperception can and must nvolve

the infallible nd immediatespiritualawarenessof a purely privatementalobjectneed notinfect causal theory fperception.But this snot the only Cartesian illusion that the philosophical study of

perception s heir to. There is also the idea that the exercise of anyhumanpowercan be bisected ntotwostreams, nepurelymental,theother nvolving urbodies and ourenvironment. he illusionthat this







THECAUSALTHEORY OF PERCEPTION 291

conceptual manoeuvre is a feasible one has been attacked by manyeminentphilosophers his entury,ncludingStrawson.Butsomethinglike a failureof nerve must have preventedthe attack frombeing

pressedhome,for hevery ame illusion ies at theheart of the causaltheory,whichrequires hatweperform recisely hismanoeuvrewhenwe offer 'strict ccount' oftheexperiencethat our sensesgrantus.

One source of thisCartesian illusionmay be, as Strawsonsays, acertain experience of intense looking within, or introspectiveconcentration, f which most of us are capable and which certainlyseems to have been characteristicfDescartes'own meditations.'22utanother, suspect, sa commitment ocategorialpurity,whichalso has

deep rootsbeyondphilosophy.23or surelythenotion that see' and'hear', althoughthey re notpuresensationverbson a parwith ache'and 'tickle',mustbe compounded out of various elements ncludingones which standforpure sensationsgains some of tsappeal from n

impulsetokeep themental and thephysicalapart. The experienceof

seeing a rose or hearingthepeal of bellsmay be a different ind of

episodetoan ache ora tickle, ut t mustbe a purely ubjective pisodeof some kind, for how could somethingmental reach beyond the

confines fsubjectivitynd embrace brutematter?Ifwe want toescape from hisdead end,we need to remember hat

doing philosophy with categorial predicates is like painting bynumbers. 'Event', 'state', 'process', 'disposition', 'mental' and

'physical', s employedby philosophers,re termswhichweredesignedforprofessional se. Butfarfrom eingthe mostrefined nstrumentsf

thoughtavailable, theyare the bluntest. So-called dispositions,for

example, have been said to include flexibility,olubility n water,medical tendencies

suchas

hay-fever),raitsof

character,colours,soundsorsmells; nd this sto gnore heextravagantuseoftheconceptbybehaviourists.

Psychologicalpredicates re no lessmotley,whatever onceptsmaydisguise the fact. So, if perceptual verbs appear to mix twoirreconcilable ategories, he mental and thephysical,we should nothasten to dismantlethem n thehope thatthey re built out of moreconformable elements. On the contrary,we should renounce an

opposition fourownmakingwhichcreatesthe llusion f taxonomic

problem.

22 Strawson, Self,Mind and Body', inFreedomndResentment,75.23 For example, Mary Douglas suggests hat t explainscertainJewishdietary aws:

'anomolouscreatures re unfit or ltar and table' (Implicit eaningsLondon: Routledgeand Kegan Paul, 1975), 266).







292 JOHN HYMAN

VIII

The causal theoryncorporates distinctivepistemology,swell as the

psychologicaldoctrinewe have examined. For example, suppose we

are sitting ogethernmyroom,which s on thegroundfloor nd looksontoa garden. I am on thewindowseat,withmyback to the window:

youareseated on a chair,facingme.As a man walkspastthewindow

say 'Fred is smartlydressedtoday.' You ask me how I know,and I

reply, I can see him. (There is a mirror n thewall behind you.)'Accordingto the causal theory,myanswersays thata psychologicalepisodeof distinctive ind s thegroundformyudgement. I see thatFred is smartlydressed today' is equivalent in meaning to the

conjunctionof threepropositions:

(1) It seems tome ust as ifFred is smartly ressedtoday;(2) Fred is smartly ressedtoday;(3) (2) causallyexplains (1);

and so the trictlyorrect nswerto thequestion How do youknow?' snot 'I can see him' (i.e. theconjunctionof (1), (2) and (3)) but (1)

alone: 'It seems to me ust as if. . .24The distinctive pistemology hat the causal theory ncorporates sthis: tatementswhichidentifyr describeperceptiblefeatures f the

speaker'senvironment e.g. 'Fred is smartlydressedtoday') and the

corresponding erceptualstatements e.g. 'I see thatFred is smartlydressedtoday') are alike based on the evidence of certain distinctivekindsofpsychological pisode.

This, I submit,s false.A perceptualverbwhich sused nresponse oan

epistemic hallenge('Fred is

smartlyressed

today.''How do

youknow?' 'I can see him.') does not invoke the corroborationof apsychological pisode. My replydefendsmy right o make theoriginalstatement;but not by introducing ny sort of evidence at all. Howthen?By affirminghat theopportunityonditions orvisiondo infactobtain:hereally svisiblefromwhere amsitting contrary owhatyou

24 This is clear from trawson'spropositions, II and IV ('Causation in Perception',67). Proposition saysthat I see thatp' entailsp. 'I see thatp' is therefore nsuitable s a

replyto thequestion, How do youknowthatp?', for twould be tantamount osaying,'How do I know?Well,for ne thingp;for nother ..' PropositionsI and IV saythat Itseems to me ust as ifp' presumptivelymplieshatp and also that see thatp. Presumptiveimplicatiohs a certainrelationweakerthanentailment' uchthatwhere presumptivelyimplies andp istrue,normallyrgenerally'is also true. Ibid.) Hence the trictlyorrectreply othe uestion,How do youknowthat ?' is It seems o me ustas ifp': am entitledto affirmhatp because it seemsto me ustas ifp, nd if tseemsto me ustas ifp,normallyorgenerally .







THECAUSALTHEORYOF PERCEPTION 293

might uppose), because there s a mirror n the wall behindyou. Inotherwords,myreply aysthat contrary o whatyoumight uppose) Iam, literally,n a positionto admireFred's dress.25

When I saywhatI can seeorhear,whether r notI usea perceptualverb whether say Fred issmartly ressedtoday'or I see thatFredis

smartlydressed today'), I affirm propositionfor which no other

proposition rovides vidence.A perceptual tatementsnotsupportedby another describing a psychological episode. There are manypropositions which are supported by another describing a

psychological pisode:for xample, know thatthewine s ntoxicatingbecause I feeltipsy; know that thewateris chlorinatedbecause my

eyes restinging.Atastretch, e can imagine visualexample:

Iknowthat theeclipse is underway, not because I can see thesun (it is too

bright or hat)butbecause I blinked t it, nd myafter-images ikeabiscuitwith a bite taken out of it. But although getting tipsy s a

pleasant way of findingout whether the contents of a bottle are

intoxicating,t snottheexercise f a cognitive apacity,as seeingand

hearing are. And thismeans precisely, hat propositionswhich saywhat thespeakersees or hears ('Fred is smartly ressedtoday', Hisvoice ishoarse',etc.) are not based on evidence.

IX

The psychology mplicit n the causal theoryof perceptioncan be

expressed n thefollowing roposition: nyperceptualstatement,uchas 'He has spotted misprintn the first age', 'I heard theprofessor'sinaugural lecture', etc., is equivalent to a reportof a psychologicalepisode plus a causal hypothesiswhich is meant to explain whythis

episodeoccurred.The epistemology mplicit n thetheorys bound upwith tspsychology; or fperceptualstatements efer opsychologicalepisodes,thenperceptual knowledgemust be knowledgebased on theevidence that these pisodes provide.

I havearguedthatthesepsychological nd epistemological octrinesare both false.Sightand hearing recognitive apacities.Butthisdoesnot mean capacities for various kinds of experiencewhich can be

i The question How do youknow?'or How did youknow?' need not be a challenge.It maysimply skwhat theperceptualmodality fknowledge s in this ase, if his s notobvious. Forexample, f tellyouthat omeone s urking ehindthe rrasand youaskmehow know, might ay I can see hisfeet oking ut',or'I can hear hisbreathing.' heseanswers specifythe perceptual modality of my knowledge, and therefore ntailcorresponding ounterfactual onditionals. (E.g. in dimmerlight I would not havenoticed;or, f had beenwhistling, wouldnot have heardhim.)Butthey o not nvokedifferentsychological pisodesas thegroundformyudgement.







294 JOHN HYMAN

reportedbysaying It seemstome (or himorher) ust as if. . . ' andwhichnormally rovideuswith reliableguideto oursurroundings.tmeanscapacitiestoacquire knowledgewhich snotbased on evidence.

These capacitiesare generallyreliable,within imits nd withvariousqualificationsto do with thehard ofhearingand the short-sighted.Equally, a statementwhichsayswhat the peaker aw or heard softenreliable, which is why an eye-witness s an asset in court. The

psychological pisodeswhichtellus,moreor lessreliably, bout ourenvironment re a different atter ntirely. hey includethearthritic

pains thatare associated withhumidity nd thestingingnmyankleswhichtellsme that there re stinging ettles bout. If I cannot see the

nettles, hen shall needsomesort f vidence thatthey re there.But fI can see them, havenoneed of vidence: neither hecorroboration fa psychological pisode,noranother'stestimony,oranyotherkindofevidence.

The psychology implicit in the causal theory is thoroughlyCartesian.Aswe have seen,Strawsonexplicitly ejects hepropositionthatthe mmediateobjectsofperceptualawarenessare psychologicalentities f some sort. But the causal theory s still committedto theCartesian llusion hat theordinary otion fperceiving's a compositenotion,which can be divided into itspurelymental and itsphysicalcomponents, each of which can exist without the other. And its

epistemologysequallyCartesian: theepistemological riorityfmindoverbodyguaranteesthat thefoundations fempiricalknowledge re

incorrigible. or if say, It seemstome as if... ', who can gainsayme?

Against hisview haveargued,first,hatperceptual xperience ndillusion re not twospeciesofthe same psychologicalgenusand hencethe concept ofperceivingcannot be dismembered n thisway; and

second,that there s no epistemological eason for ryingo dismemberit, incethefoundationsf mpiricalknowledge repropositions tatingwhat thespeakerperceives.These propositionsre corrigible:we buildonclay,notrock.This isquitestableenoughfor racticalpurposes, ndeven impracticalphilosophersong ago abandoned the view thatoursciencewill befragile r nsecureunless tsfoundationsreirrefragable.

X

So far have talkedexclusively bout sight nd hearing;I have said

nothing odistinguish etween the differentenses;and I have shownlittle ympathy or he causal theory.n conclusion, want todo a littleto remedythesedefects.For thereis no reason to believe that the

concepts of sight, hearing, smell, taste and touch have the same








structure.ndeed there severyreason to believe thattheydo not.Andso an argumentfocussed on sighthas littlebearing on touch, for

example.As it turns ut, the causal theory pplies perfectlyomanycases of

touch.Consideran example. I am lying n thegrass nthe un,withmyeyes losed.My arms are acrossmychest.All isstill.And then feel he

ticklingfan insectonmyarm. I movemyarmslightly,nd the nsectflies way.

(1) It seemedtome ust as if felt n insecton myarm;(2) the sensationwas caused byan insecton myarm;

(3) I felt he nsect.

(1), which sequivalent nmeaningto It felt s if herewas an insect n

my rm',describes heticklingensationthat felt; 2) sayshowitwascaused; (3) is a perceptual tatement. ut theconjunction f(1 and (2)seem tosaypreciselywhat (3) says.

Thiscasewas tailor-made or he causal theory.Other cases of touchdo not fit o neatly nto theprescribed cheme,because the sensation

which scaused byan objectthat stouchedcannotalwaysbe describedwith he ppropriate It seemstome...' sentence.Forexample, takeacoinout ofmypocket,and havingfelt round it with the tipsofmyfingers, am able to say that it has sevensides. It is also true thatitcauseda sensationnthetipsofmyfingers hich snormally aused bycoolmetal. can describethis ensationbysaying, tsensibly eemedtome as ifmyfingertips ere touchingcool metal; but not, it sensiblyseemedto me as ifmyfingertips eretouching sevensided coin.26

It isstartling

o discover that the causaltheory,

which distorts he

concept f ight, ppliesneatlytomanycasesof touch.Butperhapsweshould not be surprised.The veryfirst ffortso explain the phen-omenonofsightwere stimulatedbytheapparent disanalogybetween

sight nd touch,for twas thefact that we can learn about the world

apparentlywithout coming into contact with it that seemed so

puzzling.27 nd so from hebeginning, ncientphilosopher-scientists

26However, t s inconceivablethat could perceive omething ytouch without ny

sensation eingcaused at all. Ifthismeans that theconceptof ensation s implicitn theconcept f tactileperception, hen t is also true that theconceptofa causal connectionis mplicitn theconceptof tactileperception sincetheconceptof a causal connection simplicitn theconceptofsensation), althoughnot in precisely heway that the causaltheoryfperception equires.The conceptof a causal connection s also implicit n theconceptof auditory perception, although not in the way that the causal theoryofperception equires:we hearsounds, nd sounds are made (i.e. caused).27

SeeJ. Hyman, The mitationfVatureOxford:Basil Blackwell,1989), xi-xiii.







296 JOHN HYMAN

postulated ome sort f rsatz ontactbetweenthevisibleobjectand the

eye,and thendisagreedover what sortofcontact thiswas. They tried,in otherwords,toexplain sight n terms f touch. Plusfachange!

TheQueen's ollege, xford

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Hyman 1992_The Causal Theory of Perception