The’primaryqualities’donotcorrespondinthiswaytoanobjectiveworldradicallyopposedtothesubjective。Spaceisnotaformofthings，butaformimposeduponthedataofexperiencebytheminditself。This，asKantsays，supposesarevolutioninphilosophycomparabletotherevolutionmadebyCopernicusinastronomy。Wehavecompletelytoinvertourwholesystemofconceivingtheworld。WhateverthevalueofKant’sdoctrine，ofwhichIneedheresaynothing，itwasundoubtedlymoreprolificthanReid’s。Reid’swasfarlessthoroughgoing。Hedoesnotdrawanewlinebetweenobjectandsubject，butsimplyendeavourstoshowthatthedilemmawasduetocertainassumptionsaboutthenatureof’ideas。’Therealhadbeenaltogetherseparatedfromthephenomenal，ortruthdivorcedfromfact。Youcanonlyhavedemonstrationsbygettingintoaregionbeyondthesensibleworld；whilewithinthatworld——thatis，theregionofordinaryknowledgeandconduct——youaredoomedtohopelessuncertainty。Anescape，therefore，mustbesoughtbysomethoroughrevisionoftheassumedrelation，butnotbyfallingbackupontheexplodedphilosophyoftheschools。ReidandhissuccessorswerequiteasmuchaliveasLocketothedangeroffallingintomerescholasticlogomachy。They，too，willinsomesensebaseallknowledgeuponexperience。ReidconstantlyappealstotheauthorityofBacon，whomheregardsasthetruefounderofinductivescience。ThegreatsuccessofBacon’smethodinthephysicalsciences，encouragedthehope，alreadyexpressedbyNewton，thatasimilarresultmightbeachievedin’moralphilosophy。’21*Humehaddonesomethingtocleartheway，butReidwas，asStewartthinks，thefirsttoperceiveclearlyandjustlythe’analogybetweenthesetwodifferentbranchesofhumanknowledge。’Themindandmatteraretwoco-ordinatethings，whosepropertiesaretobeinvestigatedbysimilarmethods。Philosophythusmeansessentiallypsychology。Thetwoinquiriesaretwo’branches’ofinductivescience，andtheproblemistodiscoverbyaperfectlyimpartialexaminationwhatarethe’fundamentallawsofmind’revealedbyanaccurateanalysisofthevariousprocessesofthought。
ThemainresultofReid’sinvestigationsisgivenmostpointedlyinhisearlyInquiry，andwasfullyacceptedbyStewart。Brieflyitcomestothis。Noonecandoubtthatwebelieve，asafact，inanexternalworld。Webelievethattherearesunandmoon，stones，sticks，andhumanbodies。Thisbeliefisacceptedbythescepticaswellasbythedogmatist，althoughthescepticreducesittoamereblindcustomor’associationofideas。’NowReidarguesthatthebelief，whateveritsnature，isnotandcannotbederivedfromthesensations。Wedonotconstructthevisibleandtangibleworld，forexample，simplyoutofimpressionsmadeuponthesensesofsightandtouch。Toprovethis，heexamineswhataretheactualdataprovidedbythesesenses，andshows，ortriestoshow，thatwecannotfromthemaloneconstructtheworldofspaceandgeometry。Hence，ifweconsiderexperienceimpartiallyandwithoutpreconception，wefindthatittellsussomethingwhichisnotgivenbythesenses。Thesensesarenotthematerialofourperceptions，butsimplygivetheoccasionsuponwhichourbeliefiscalledintoactivity。Thesensationisnomoreliketherealityinwhichwebelievethanthepainofawoundisliketheedgeoftheknife。Perceptiontellsusdirectlyandimmediately，withouttheinterventionofideas，thatthereis，asweallbelieve，arealexternalworld。
Reidwasavigorousreasoner，andcredithasbeengiventohimbysomedisciplesofKant’sdoctrineoftimeandspace。Schopenhauer22*saysthatReid’s’excellentwork’givesacomplete’negativeproofoftheKantiantruths’；
thatistosay，thatReidprovessatisfactorilythatwecannotconstructtheworldoutofthesense-givendataalone。But，whereasKantregardsthesensesassupplyingthematerialsmouldedbytheperceivingmind，Reidregardsthemasmerestimuliexcitingcertaininevitablebeliefs。AsaresultofReid’smethod，then，wehave’intuitions。’Reid’sessentialcontentionisthatafairexaminationofexperiencewillrevealcertainfundamentalbeliefs，whichcannotbeexplainedasmeremanifestationsofthesensations，andwhich，bytheveryfactthattheyareinexplicable，mustbeacceptedasan’inspiration。’23*
Reidprofessestodiscoverthesebeliefsbyaccuratelydescribingfacts。