TocarryoutthistheoryisthecentralaimofHamilton’s’NaturalRealism。’Reid’sstatementmightseemtobenotablunder，butatruism。’Iamconsciousoftherose’meansprecisely’IhavecertainsensationswhichIregardasimplyingtheexistenceofapermanentexternalreality。’Butthisistointerpretperceptionasinvolvingan’inference，’andtherefore，accordingtoHamilton，istoabandontheessentialdoctrineofNaturalRealism。29*Itmayseemstrange，headmits，butitistrue，’thatthesimpleandprimaryactofintelligenceshouldbeajudgment，whichphilosophersingeneralhavereceivedasacompoundandderivativeoperation。’30*’Knowing’and’knowingthatweknow’arethesamething；asconceivingthesidesandanglesofatrianglearethesameprocess，distinguishableinthought，but’innature，oneandindivisible。’31*What，then，isthisessentialjudgment？Inanactofsensibleperception，saysHamilton，Iamconsciousofmyselfandofsomethingdifferentfrommyself。32*Thismightseemtodefinethedistinctionbetween’consciousness’and’perception。’theobjectofmythoughtmay，asHamiltonremarks，bea’modeofmind’aswellasa’modeofmatter。’33*Consciousnessofself，weshouldinfer，differsfromconsciousnessofthenot-self，anditisjustthepresenceofthenot-selfwhichdistinguishesperceptionfromsimpleconsciousness。Hamilton，however，arguesthatperceptionissimpleconsciousness；orthatthedistinction，forhispurpose，isirrelevant。Thereisa’logical’butnota’psychological’difference。34*Everyactofconsciousnessimpliesaconceptionoftheego。But’thescienceofoppositesisone。’thereforeconsciousnessoftheegoinvolvesconsciousnessofthenon-ego，or，inthesimplestpossibleactofintelligenceImustbetakentoaffirmtheexistencebothofanegoandanon-ego。
IfIcannoteventhinkaboutmyselfwithoutaffirmingtheexistenceofanexternalworld，itwouldbesuperfluoustolookaboutforfurtherproofsofitsexistence。Buthereoccursasingulardifficulty。Hamiltonhastoguardagainstthetranscendentalistaswellasagainstthesceptic。Heisthereforenotonlya’realist，’butwithequalemphasisa’relativist。’
thatourknowledgeisessentiallyrelativeisoneofthepointsuponwhichheinsistsmostemphatically，andconfirmsasusualbyacatenaofauthorities。Itis，hesays，thetruth’mostharmoniouslyre-echoedbyeveryphilosopherofeveryschool，exceptthemodernGermans。’35*Thephraserelativityhasmorethanonemeaning；butaccordingtoHamiltonmeansatleastthis：
’ourwholeknowledgeofmindandmatterisrelative——
conditioned——relativelyconditioned。’Ofmindandmatter’inthemselves’weonlyknowthattheyare’incognisable。’’Allthatweknowisthereforephenomenal——phenomenaloftheunknown。’