Theprincipleswhicharisefromtheirreferencetothesensibleworld，onlyserveourunderstandingforempiricaluse。Beyondthistheyarearbitrarycombinations，withoutobjectivereality，andwecanneitherknowtheirpossibilityapriori，norverifytheirreferencetoobjects，letalonemakeitintelligiblebyanyexample;becauseexamplescanonlybeborrowedfromsomepossibleexperience，consequentlytheobjectsoftheseconceptscanbefoundnowherebutinapossibleexperience。Thiscomplete（thoughtoitsoriginatorunexpected）solutionofHume’sproblemrescuesforthepureconceptsoftheunderstandingtheiraprioriorigin，andfortheuniversallawsofnaturetheirvalidity，aslawsoftheunderstanding，yetinsuchawayastolimittheirusetoexperience，becausetheirpossibilitydependssolelyonthereferenceoftheunderstandingtoexperience，butwithacompletelyreversedmodeofconnectionwhichneveroccurredtoHume，notbyderivingthemfromexperience，butbyderivingexperiencefromthem。Thisisthereforetheresultofallourforegoinginquiries：\"Allsyntheticalprinciplesaprioriarenothingmorethanprinciplesofpossibleexperience，andcanneverbereferredtothingsinthemselves，buttoappearancesasobjectsofexperience。Andhencepuremathematicsaswellasapurescienceofnaturecanneverbereferredtoanythingmorethanmereappearances，andcanonlyrepresenteitherthatwhichmakesexperiencegenerallypossible，orelsethatwhich，asitisderivedfromtheseprinciples，mustalwaysbecapableofbeingrepresentedinsomepossibleexperience。\"Sect。31。Andthuswehaveatlastsomethingdefinite，uponwhichtodependinallmetaphysicalenterprises，whichhavehitherto，boldlyenoughbutalwaysatrandom，attemptedeverythingwithoutdiscrimination。Thattheaimoftheirexertionsshouldbesonear，struckneitherthedogmaticalthinkersnorthosewho，confidentintheirsupposedsoundcommonsense，startedwithconceptsandprinciplesofpurereason（whichwerelegitimateandnatural，butdestinedformereempiricaluse）inquestoffieldsofknowledge，towhichtheyneitherknewnorcouldknowanydeterminatebounds，becausetheybadneverreflectednorwereabletoreflectonthenatureorevenonthepossibilityofsuchapureunderstanding。Manyanaturalistofpurereason（bywhichImeanthemanwhobelieveshecandecideinmattersofmetaphysicswithoutanyscience）maypretend，thatlielongagobythepropheticspiritofhissoundsense，notonlysuspected，butknewandcomprehended，whatisherepropoundedwithsomuchado，or，ifhelikes，withprolixandpedanticpomp：\"thatwithallourreasonwecanneverreachbeyondthefieldofexperience。\"Butwhenheisquestionedabouthisrationalprinciplesindividually，hemustgrant，thattherearemanyofthemwhichbehasnottakenfromexperience，andwhicharethereforeindependentofitandvalidapriori。Howthenandonwhatgroundswillherestrainbothhimselfandthedogmatist，whomakesuseoftheseconceptsandprinciplesbeyondallpossibleexperience，becausetheyarerecognizedtobeindependentofit？Andevenhe，thisadeptinsoundsense，inspiteofallhisassumedandcheaplyacquiredwisdom，isnotexemptfromwanderinginadvertentlybeyondobjectsofexperienceintothefieldofchimeras。Heisoftendeeplyenoughinvolvedinthem，thoughinannouncingeverythingasmereprobability，rationalconjecture，oranalogy，begivesbyhispopularlanguageacolortohisgroundlesspretensions。Sect。32。Sincetheoldestdaysofphilosophyinquirersintopurereasonhaveconceived，besidesthethingsofsense，orappearances（phenomena），whichmakeupthesensibleworld，certaincreationsoftheunderstanding（Verstandeswesen），callednoumena，whichshouldconstituteanintelligibleworld。Andasappearanceandillusionwerebythosemenidentified（athingwhichwemaywellexcuseinanundevelopedepoch），actualitywasonlyconcededtothecreationsofthought。Andweindeed，rightlyconsideringobjectsofsenseasmereappearances，confesstherebythattheyarebaseduponathinginitself，thoughweknownotthisthinginitsinternalconstitution，butonlyknowitsappearances，viz。，thewayinwhichoursensesareaffectedbythisunknownsomething。
Theunderstandingtherefore，byassumingappearances，grantstheexistenceofthingsinthemselvesalso，andsofarwemaysay，thattherepresentationofsuchthingsasformthebasisofphenomena，consequentlyofmerecreationsoftheunderstanding，isnotonlyadmissible，butunavoidable。Ourcriticaldeductionbynomeansexcludesthingsofthatsort（noumena），butratherlimitstheprinciplesoftheAesthetic（thescienceofthesensibility）
tothis，thattheyshallnotextendtoallthings，aseverythingwouldthenbeturnedintomereappearance，butthattheyshallonlyholdgoodofobjectsofpossibleexperience。Herebythenobjectsoftheunderstandingaregranted，butwiththeinculcationofthisrulewhichadmitsofnoexception：
\"thatweneitherknownorcanknowanythingatalldefiniteofthesepureobjectsoftheunderstanding，becauseourpureconceptsoftheunderstandingaswellasourpureintuitionsextendtonothingbutobjectsofpossibleexperience，consequentlytomerethingsofsense，andassoonasweleavethisspheretheseconceptsretainnomeaningwhatever。\"Sect。33。Thereisindeedsomethingseductiveinourpureconceptsoftheunderstanding，whichtemptsustoatranscendentuse，——ausewhichtranscendsallpossibleexperience。Notonlyareourconceptsofsubstance，ofpower，ofaction，ofreality，andothers，quiteindependentofexperience，containingnothingofsenseappearance，andsoapparentlyapplicabletothingsinthemselves（noumena），but，whatstrengthensthisconjecture，theycontainanecessityofdeterminationinthemselves，whichexperienceneverattains。
Theconceptofcauseimpliesarule，accordingtowhichonestatefollowsanothernecessarily;butexperiencecanonlyshowus，thatonestateofthingsoften，oratmost，commonly，followsanother，an（ithereforeaffordsneitherstrictuniversality，nornecessity。HencetheCategoriesseemtohaveadeepermeaningandimportthancanbeexhaustedbytheirempiricaluse，andsotheunderstandinginadvertentlyaddsforitselftothehouseofexperienceamuchmoreextensivewing，whichitfillswithnothingbutcreaturesofthought，withouteverobservingthatithastransgressedwithitsotherwiselawfulconceptstheboundsoftheiruse。Sect。34。Twoimportant，andevenindispensable，thoughverydry，investigationshadthereforebecomeindispensableintheCritiqueofPureReason，—viz。，thetwochapters\"VomSchematismusderreinenVerstandsbegriffe，\"and\"VomGrundederUnterscheidungallerVerstandesbegriffeuberhauptinPhenomenaundNoumena。\"Intheformeritisshown，thatthesensesfurnishnotthepureconceptsoftheunderstandinginconcreto，butonlytheschedulefortheiruse，andthattheobjectconformabletoitoccursonlyinexperience（astheproductoftheunderstandingfrommaterialsofthesensibility）。