Inthefirstplace，itmustbenoticedthatthetheoryitselfhadbeenalreadyemphaticallystatedbyDestuttdeTracy。HamiltonaccusesBrownofplagiarism。21Whetherhisaccusationbejustifiableornot，itiscertainlytruethatBrownhadinsomewayreachedthesameprincipleswhichhadbeenalreadysetforthbyaleading’ideologist’Brown，thatis，thoughtheofficialexponentoftheScottishphilosophy，wasinthisphilosophicaltenetatonewiththeschoolwhichtheyregardedasmaterialisticorsceptical，thepathbywhichhereacheshisconclusionsisalsocharacteristic。
　　BrownhasreversedtheinterpretationofReid’sexperimentumcrucis，Iwillgiveupmycase，saysReid，ifyoucanmaketheexternalworldoutofsensations，that，repliesBrown，ispreciselywhatwecando。HowfromsensationsdowegetwhatBerkeleycalled’outness’?Wegetit，saysBrown，fromthesenseofresistanceor’impededeffort，’thatrevealstousthefactthatthereissomethingindependentofourselves，andthebeliefinsuchasomethingispreciselywhatwemean，andallthatwemean，bythebeliefinanexternalworld。，Consistentlywiththis，BrownrejectsReid’sdistinctionbetweentheprimaryandsecondaryqualities。Thedistinctioncorrespondsnodoubttosomerealdifferences，butthereisnodifferenceofthekindsuggestedbyReid。’All[thequalities]
　　arerelativeandequallyrelative——ourperceptionofextensionandresistanceasmuchasourperceptionoffragranceandbitterness。’22Weascribethesensationsto’externalobjects，’buttheobjectsareonlyknownbythe’medium’ofoursensations。Inotherwords，thewholeworldmayberegardedasasetofsensations，whetherofsight，smell，touch，orresistancetomuscularmovement，accompaniedbythebeliefthattheyarecausedbysomethingnotourselves，andofwhichsomethingwecanonlysaythatitisnotourselves。
　　Oncemore，theanalysisoftheprocessbywhichthebeliefisgeneratedissignificant。Fromresistance，orthesensationproducedwhensomething’resistsourattemptstograspit，’wegetthe’outness，’thenperceptionis’nothingmorethantheassociationofthiscomplexnotionwithourothersensations——thenotionofsomethingextendedandresisting，suggestedbythesesensations，whenthesuggestionsthemselveshavepreviouslyarisen，andsuggestedinthesamemannerandonthesameprincipleasanyotherassociatefeelingsuggestsanyotherassociatefeeling。’23Theodourorcolourofaroserecallsthesensationoftouchingandofresistancetoourgrasp。Thusweregardthewholegroupofsensationsasduetotheexternalcausewhichproducesthesensationofresistance。Brownseemstohesitatealittleastowhetherheshallappealtoan’intuition’orto’association，’but’asIratherthink，’hesays，thebeliefisfounded’onassociationsaspowerfulasintuition，’24
　　Whatever，then，maybetheoriginofthebelief——’intuition’or’association’——itisclearthatitcangiveusnoknowledgeexceptsuchasisderivedfromsensations。
　　Moreover，Brownisthusled，asinthedoctrineofcausation，toacceptareallyscepticalposition。HedeclaresthatheisinthisrespectatonewithbothReidandHume。Theybothaccepttwopropositions：first，thatwecannot’bymerereasoning’provetheexistenceofanexternalworld；
　　secondly，thatitis’absolutelyimpossibleforusnottobelieve’initsexistence。Hume，hesays，pronouncesthefirstpropositionina’loudtoneofvoice’and’whispers’thesecond。Reid，conversely，passesoverthefirstrapidlyand’dwellsonthesecondwithatoneofconfidence。’25Brownacceptsbothstatements。HehasalreadysaidthatthereisnoargumentagainstBerkeley’sdenialofmatteranymorethanagainstthe’infinitedivisibilityofmatter。’Butheadds，itis’physicallyimpossible’forustoadmittheconclusion，atleastwithout’aninstantdissentfromamomentarylogicaladmission。’26This，indeed，isbutaversionofHume’sfamiliarstatementthatBerkeley’sargumentsadmitofnoreplyandproducenoconviction。
　　AnotheressentialdoctrineoftheMills，the’association’theory，istreateddifferentlybyBrown。
　　Brown，aswehaveseen，bothinhistheoryofcausationandinhistheoryofourbeliefinanexternalworld，speaksofprinciplesinthemindwhichsomehowoverride’ratiocination，’inthefirstcase，hespeaksof’intuition，’
　　butintheother，asIhavesaid，heseemstopreferassociation，thedifferenceisremarkablebecausethebeliefinanexternalworldisuponhisshowingsimplyacaseofcausation。Itmeansessentiallythereferenceofoursensationsastoanexternalcause。Now，intheargumentuponcausation，hehasinsistedupontheinsufficiencyofassociationtogeneratethebelief；andhewouldhavefounditdifficulttomeethisownargumentsifappliedtothebeliefinanexternalworld。YetitdoesnotseemtooccurtohimthatthereisanydifficultyinexplainingthisbeliefinanexternalworldasacaseofwhatMillcalled’indissolubleassociation。’Brown，asMillthought，wasnotsufficientlyawareofthepowerofthisprinciple，andthedifferencebetweenthemismarkedbythisdivergence。Brownhadagreatdealtosayaboutassociation，thoughhechosegenerallytosubstitutetheword’suggestion，’
　　previouslyfamiliartoReidandBerkeley。27Heconsidersit，however，mainlyinanotherrelation。Heproposestotracetheorderinwhich’trains’ofideassucceedeachotherinourminds。Hedoesnotdwellupontheinfluenceofassociationinproducingbelief。Hisquestionisnotprimarilyastothelogic，butastotheactualsuccessionofourthoughts。
　　Heexplainsthatheusestheword’suggestion’inordertoavoidthehypothesisthatthesequenceoftwoideasnecessarilyimpliesapreviousstateofmindinwhichtheywerebroughttogether；andendeavourstoexplainvariouscasesas，forexample，associationby’contrast’aswellasby’likeness’
　　or’continuity’byamore’subtile’analysis。28Hethenworksoutanelaboratetheoryof’simple’and’relative’suggestion。Simple’suggestion’29correspondsmainlytoordinaryassociation，aswhenafriend’snameorhisbookcallsupthethoughtofthemanhimself。’Relativesuggestion’
　　ariseswhentwoormoreobjectsareperceivedandsuggestvariousrelationsoflikenessandsoforth。30Thisprovidesaschemeforworkingoutthewholedoctrineofthesequencesofideassofarasthesequencesdependupontheminditselfandnotuponexternalcauses。Itthusleadstoproblemsofabstractionandgeneralisationandtohiswholetheoryofwhathecallsthe’intellectualstates。’HeagaincloselycoincideswiththeFrenchideologists。HestartsbyexaminingLockeandCondillac。HeofcourseprofessestoholdthatCondillac’sversionofLockeisillegitimate，andridiculesthefamousformulapenserc’estsentir。Heis，however，equallyunwillingtoadmitReid’s’varietyofpowers。’31Infact，hiscriticismofCondillacshowsmoreaffinitythancontrast。Condillacerred，hesays，inholdingthatthoughtsare’transformedsensations。’ThiswasafalsesimplificationintowhichheconsidersCondillactohavebeenledpartlybytheambiguityofthewordsentir。32Condillacappliedtothemindthetheory，truein’thechemistryofthematerialchemists，’
　　thatthe’compoundsaretheelementsthemselves。’33Heerrswhenheinfersfromtheanalogythatafeelingwhicharisesoutofotherscanberesolvedintothem。’Loveandhate’andotheremotionsarefundamentallydifferentfromthesensationsbywhichtheyareoccasioned，notmere’transformations’
　　ofthosesensations。We，ontheotherhandthatistosay，ReidandStewart，haveerredbyexcessiveamplification。Insteadofidentifyingdifferentthings，wehaveadmittedasuperfluousnumberof’ultimateprinciples。’
　　Theresultisthatbesidestheoriginalsensations，wehavetoconsideranumberoffeelings，which，whileessentiallydifferent，are’suggested’orcausedbythem。Thesearepartsofthewholeintellectualconstruction，and，thoughnottransformedsensations，arestill’feelings’arisinginconsequenceofthesensations。
　　Theyarepartsofthe’trains’orsequencesof’ideas。’ItisaccordinglycharacteristicofBrownthathehabituallydescribesanintellectualprocessasa’feeling，’thestatementofamathematicalproportion，forexample，isacaseof’relativesuggestion。’Whenweconsidertwonumberstogetherwehavea’feelingoftherelationofproportion。’34The’profoundestreasonings’are’nothingmorethanacontinuedanalysisofourthought，’
　　bywhichweresolvethe’complexfeelingsofourminds’intothesimplerconceptionsoutofwhichtheywereconstructed。35Inotherwords，Brown，itwouldseem，reallyacceptsthepenserc’estsentir，onlythatheregardsthesentirasincludingseparateclassesoffeeling，whichcannotberegardedassimple’transformations’ofsensation。Theyare’statesofthemind’causedby，thatis，invariablyfollowingupon，thesimplerstates，and，ofcourse，combininginanendlessvarietyofdifferentforms。
　　Reasoningisnothingmorethanaseriesofrelative’suggestionsofwhichtheseparatesubjectsarefeltbyustobemutuallyrelated。’36Hence，too，ariseshistheoryofgeneralisation。Heis，hesays，nota’nominalist’buta’conceptualist，’andhere，foronce，agreeswithReidasagainstStewart。37The’generalterm，’accordingtohim，expressesthe’feelingorgeneralnotionofresemblance，’whicharisesuponacontemplationoftwoobjects。’InNature，’asheobserveselsewhere，38’therearenoclasses，’buttheobservationofanumberofparticularcasesandacertainfeelingtowhichwegiveaname。Here，again，Brown’sviewcoincideswiththatofhisFrenchcontemporaries。
　　WemaythensaybrieflythatBrowncarriesoutinhisownfashiontheconceptionofpsychologywhichmakesitaninductivescienceparalleltothephysicalsciences，andtobepursuedbythesamemethods。Wehavetodowith’feelings’insteadofatoms，andwithmentalinsteadof’material’chemistry。Oursolemethodisstillananalysissuchasguidesusinunravellingcomplexphysicalphenomena。Wehave，indeed，toadmitcertainfirsttruths——thebeliefinourownidentityisoneofthem——whicharenecessarytoourveryexistence，althoughtheassertionofsuchprincipleswascarriedtoanextravagantandridiculouslength’byReidandsomeofhisfriends。’When，however，wecometoaskwhattheseprinciplesare，itmustbeadmittedthattheyareveryinnocent。Theyarenotdangerousthings，like’innateideas，’
　　capableofleadingustoatranscendentalworld，butsimplyassertionsthatwearewarrantedintrustingoursensationsandapplyingathoroughlyinductiveandempiricalmethod。Theyarethecementwhichjoinsthefeelings，andwhich，asMillthought，couldbesupplantedby’indissolubleassociations。’
　　Theindefinitepowerthusattributedtoassociationbecame，asweshallsee，Mill’smostcharacteristicdoctrine。Meanwhile，IwillonlymentiononeinferencewhichillustratesBrown’sphilosophicaltendencies。Stewarthadspokendoubtfullyoftheontologicalargumentfortheology。Brownthrowsitoveraltogether。Hedoesnotevenchangeitintoan’intuition。’Hehasalways，hesays，regardeditas’absolutelyvoidofforce’unlessittacitlyassumesthe’physicalargument。’Nay，itisoneproofoftheforceofthisphysicalargumentthatithassavedusfromdoubtswhichwouldberatherstrengthenedthanweakenedbythe’metaphysicalarguments。’39The’physicalargument’meanstheargumentfromdesign，whichthusbecomesthesolesupportoftheology。
　　HamiltonnaturallyregardsBrownasamerescepticindisguise。Histheoryofperceptiondestroyshistheoryofpersonalidentity。Hehasrefusedtoacceptourintuitivebeliefinonecase，andcannotappealtoitintheother。Heleavesnoroomfor’libertyofwill，’andadvances’noargumentinsupportofthisconditionofourmoralbeing。’40Indeed，asStewartcomplained，Brown，byidentifying’will’and’desire，’hasgotridofthewillaltogether。
　　Itisonlynaturalthatamanwhoismakingascientificstudyofthelawsofhumannatureshouldfindnoroomforanassertionthatwithinacertainspheretherearenolaws。Aphysiologistmightaswelladmitthatsomevitalprocessesareuncaused。