Nobody’s’consciousness，’wemaybesure，evertoldhimthatheperceivednotthesunbuttheactionofraysoflightonhiseye。
Hamiltonhasdivergedfromaconsiderationoftheconsciousnessitselftoaconsiderationofthephysicalconditionsofconsciousness。HavingstartedwithReid，henextadmitsKanttobeconclusive，andendsbyescapingtowhatisonlyexpressibleintermsofmaterialism。Thedeliveranceofconsciousnesshascometobeastatementthatmyfingersaredifferentfrommytoes，andthat，asIamfingersandtoes，Iamawareofthefact。
IwillnotaskwhetheritispossiblebyanyinterpretationtoputatenableconstructionuponHamilton’slanguage。Hamiltonbeginsbydiscardingthephilosopher’scrotchetthatthedifferencebetweenmindandmatterpreventsthemfromaffectingeachother；andnowheseemstoadmititsforcesofullythatheconceivesofthenervousorganismasakindofamalgamofmindandmatter。61*
IhavefollowedHamiltonsofarinordertoillustratethewayinwhich，bysuperposinginsteadofreconcilingtwodifferentsetsofdogma，hebecamehopelesslyconfused。TheoldScottishdoctrinereallybecomesbankruptinhisversion。HamiltonisstillstrugglingwithReid’soldproblem，andattackingthe’cosmotheticidealism’asReidattackedtheidealsystem。Howarewetocrossthegulfbetweenmindandmatter，especiallywhenweknownothingabouteithermindormattertakenapartfrommatterormind？Theproblemisinsolubleonthesetermsbecauseitisreallymeaningless。TheanswersuggestedbyKantwaseffectiveprecisely——asItakeit——becauseitdrewthelinedifferently，andthereforealteredthewholequestion。Kantdidnotprovideanewbridge，butpointedoutthatthechasmwasnotrightlyconceived。Totrytosettlewhetherthe’primaryqualities’belongto’thingsexternaltothemind’isidle。Itleadstotheinevitabledilemma。Ifthe’primaryqualities’
belongtothethingsortheobject，geometrybecomesempiricalanddeducibleonlyfromparticularexperiments，likeotherphysicalsciences。Thenwecannotaccountforitsuniquecharacteranditsatleastapparent’necessity。’If，ontheotherhand，theprimaryqualitiesbelongtothemind，wecanunderstandhowthemindevolvesorconstructs，butitisatthecostofadmittingthemtobeafterallunreal，because’subjective，’orderivingknowledgeoffactfromasimpleanalysisofthought。Butthedilemmaisreallyillusory。Wecannotsaythatthetruthsofgeometryrefereithertothings’outofthemind’ortothings’inthemind。’Theyare’subjective’inthesensethattheyareconstructedbythemindintheveryactofexperiencing。Theyarenotsubjectiveinthesenseofvaryingfromoneexperiencetoanotherorfromonemindtoanother。Theybelongtoperceptionasperception，ortotheperceiverasperceiving。Itis，therefore，meaninglesstoaskwhethertheyare’objective’or’subjective，’
ifthatistobeansweredbydeciding，asHamiltonwoulddecide，whatpartisduetothesubjectandwhatparttotheobject。Thatfeatcouldonlybeperformedifwecouldgetoutsideofourminds，whichwealwayscarryaboutwithus，oroutsideoftheuniversetowhichwearestrictlyconfined。Thenwemightperhapsunderstandwhateachfactoris，consideredapartfromtheother。
Asitis，wecanonlysaythatthetruthsareuniversalasbelongingtoexperienceingeneral，andnecessaryascorrespondingtoidenticalmodesofcombiningourexperience。Butwemustabandonthefruitlessattempttoseparateobjectfromsubject，andthentoconstructabridgetocrossthegulfwehavemade。
III。MILLONTHEEXTERNALWORLD
UponthisIhavespokensufficientlyinconsideringMill’sLogic。Mill’sfailuretoappreciatethechangeintherealissuesmadebytheKantiandoctrineinthisandotherquestionsisasourceofperplexityinhiscriticismofHamilton。62*HisstraightforwardstatementofhisownviewisareliefafterHamilton’scomplexandtortuousmodeofforciblycombininginconsistentdogmas。Heisable，moreover，toexposeverythoroughlysomeofHamilton’sinconsistencies。Butthoughhecanhitparticularerrorsveryhard，hehasnotasufficientcluetothelabyrinth。Metaphysiciansforhimarestilldividedintotwogreatschools——intuitionistsandempiricists，or，asheheresays，the’introspective’andthe’psychological’school。63*
TheScottishandtheKantiandoctrinesarestilllumpedtogether，andthereforemoreorlessmisunderstood。Henceintreatingofourbeliefinanexternalworldheisstillintheoldposition。
Kant，accordingtohim，supposesthemindnottoperceivebutitselfto’create’attributes，andthenbyanaturalillusiontoascribethemtooutwardthings。64*Themind，onthisversion，doesnotsimplyorganisebutaddsto，oroverrides，experience。
Consequentlytheexternalworldwouldbecomesubjectiveorunreal；andunlessweadmitaquasi-miraculousintuition，weareunderanecessaryillusion。MillsubstantiallystartsfromBerkeley’sposition。Thedistinctionbetweentheprimaryandsecondaryqualitiesis，heholds，illusory。Weknownothingof’object’or’subject，’’mind’or’matter’inthemselves。65*Ourknowledgeistherefore’subjective。’Ourwholeprovisionofmaterialisnecessarilydrawnfromsensations。Theproblemoccurs，howfrommeresensationswemakeanatleastapparentlyexternalworld。Millendeavourstoshowthatthisispossible，thoughhethinksthatBerkeley’sattemptwasinadequate。66*Wecanleapthegulfwithoutthehelpofanyspecialmachineryinventedforthepurpose，suchasReid’s’intuitions’orKant’sformsofperception。Heoffershisowntheoryasan’antagonistdoctrinetothatofSirWilliamHamiltonandtheScottishschool，’67*anditcertainlyhastheadvantageofsimplicity。
Milllaysdownatstarting68*thepostulatesfromwhichheistoreason。Here，ofcourse，weappealtoassociation。
Association，hetellsus，linkstogetherthethoughtsofphenomenawhicharelikeeachother，orwhichhavebeencontiguousorsuccessive；thelinkstrengthensastheassociationisrepeated，andafteratimebecomes’inseparable。’Nowbeliefinanexternalworldmeansthebeliefthatthingsexistwhenwedonotthinkofthem；thattheywouldexistifwewereannihilated；andfurther，thatthingsexistwhichhaveneverbeenperceivedbyusorbyothers。Thisbeliefisexplicablebytheknownlawsofassociation。Foratanymomentagivensensationcallsup’acountlessvarietyofpossibilitiesofsensation。’
Theyareregarded，thatis，assensationswhichImightexperienceifcircumstanceswerealtered。Again，thesepossibilitiesofsensationwhich，headds，are’conditionalcertainties’arepermanent，becausetheymaybecalledupbyanyofthefleetingsensations。Thispermanenceisoneofthecharacteristicsoftheoutsideworld；andwethushavealwaysinthebackground，orasa’kindofpermanentsubstratum，’wholegroupsof’permanentpossibilities’suggestedbythepassingsensations。Thesebecomefurtherconsolidatedwhenfixedordersofsuccessionhavesuggestedtheideasofcauseandeffect——
themselvesaproductofassociation。Hence，wegetourexternalworld，andcandefineMattertobea’PermanentPossibilityofsensation。’Thephrasebecamefamous。
ThisinvolvesthemetaphysicalquestionwhichwasreservedorevadedintheLogic。Hiswholepurposethereistoshowthatthoughtsshouldconformtothings。Buthowthingsdifferfromthoughtswasnevermadeclear。’Attributes，’wewerethentold，werethesameas’sensations。’Thesensationssomehowcohereinclusters。Butwhatmakesthemcohereindifferentforms？Whenasensationisnotaccompaniedbythesensationpreviouslyassociated，whyisnottheassociationsimplyweakenedordestroyedinsteadofsuggestinga’conditionalcertainty’？I
learnthatfireishotbecausethesensationsofbrightnessandheathaveoccurredtogether；butwhenIseethebrightnesswithoutfeelingtheheat，whydoesnottheassociationsimplybecomefainter？WhyshouldIinterprettheexperiencetomean，’IfIwerenearerIshouldfeeltheheat’？DoesnottheinterpretationimplythatIhavealreadysomesystemofcombiningmyimpressionsandaneedofmakingthetwoexperiencesconsistentinsteadofcontradictory？Uponthesingleassumptionofsensationsoccurringtogetherorsuccessively，andrelatedintimealone，thereseemstobenoneedforanyexternalworldwhatever。Thehypothesiswouldbeexemplifiedinthecaseofananimalwhich，thoughcapableofsensations，hadnocapacityforarrangingthemsoastorepresentspaceatall。And，again，thestatementsuggestsnodistinctreferencetoanycriterionoftruthorfalsehood。Itaccountsforillusionsaswellasfortruebeliefs。Whatisthedifference？Thefactthatcertainsensationsadhereinclustersisnotthesamethingasthebeliefintheirregularrecurrence；andconsideringthevastvarietyandintricacyofoursensations，thequestionwhichIhavementionedinconnectionwithJamesMillarisesagain：Whyshouldanytwopeoplehavethesameclustersoronthisshowingthesamebelief——orhowoneassociationcanbesaidtobenotrealbut
true，andanothernotunrealbutfalse？
ThisdifficultyshowsitselfwhenMillproceedstoinvestigatethe’primaryqualities。’Theyaretobesimply’attributes’co-ordinatewithotherattributes。WiththehelpofProfessorBainandMrHerbertSpencer，inwhosethenrecentwritingshesawamostencouragingdevelopmentofhisfather’sprinciples，Millmakesoutacasetoshowhowtheperceptionofspacemaybedeveloped。Theproblemdiscussedbythoseauthoritiesandtheirsuccessorsisclearlyalegitimatepartofpsychology；theirinvestigations，thoughstillonthethresholdofavastanddifficultinquiry，areatleastvaluablebeginnings；andwhentheexpertshaveallagreed，weshallbereadytoaccepttheirconclusions。Thereis，however，adifficultywhichexposesMilltoanothercriticism。69*Briefly，itisthathisso-calledexplanationofspace-conceptionreallypresupposesspace。HamiltonhadpointedthisoutinhisKantianmoods。70*Thedifficultyisobvious。Inascientifictheoryastatementintermsofspaceisanultimatestatement。Wedonottry，nordoesitappeartobepossible，togetbehindit。WhenI
havesaidthatabodymovesinanellipse。Idonotgoontoexpresstheellipseintermsof’muscularsensation。’Thatwouldbetosubstituteforadefinitemeasureoneessentiallyfluctuatinganduncertain。Icandefineagivenmuscularsensationasthatwhichcorrespondstoacertaindistance；buttoreversethedefinition——toexpressthedistanceintermsofthepuresensation，excludingallreferencetodistance，issurelyimpossible。Now，itmayseemthatMillishereattemptingjustthisimpossiblefeat。Thereforeheisreallystillonthesamesideofthegulf，thoughhesupposeshimselftohavecrossedit。
His’pigtail’accordingtothefamousapologue——still’hangsbehindhim。’Inotherwords，heismistakingapsychologicalforametaphysicalexplanation；anaccountofhowitisthatwecometoperceivespace，assumingspacetoexist，withanexplanationofwhatspaceis；andaresolutionoftheperceptionintoasetofsensationsassociatedintime。Here，again，heisunderthegreatdisadvantageofsupposingthespace-perceptiontohavebeenmadewithinthelimitsofalifetime。Ifitwerepossibletolookintothemindofaninfantwecould，hethinks，seehowtheideawasformed。71*Amodernpsychologistcanatleasthelphimselfbylookingindefinitelyfurtherbackandtracingthewholehistoryoftheorganismtotheearlierformsoflife；andthespace-perceptionceasestoimplyapreternaturaloraprioricapacity。Somethingmoreissurelywanted，thoughIdonotventuretosaypreciselywhat。Mill’sdoctrinethatmybeliefinaexternalworldisabeliefin’apermanentpossibilityofsensation’maybeacceptedinsomesense。When，forexample，I