Suppose，again，thathehasacquiredmoreexperience，andhaslivedsolongintheworldastohaveobservedfamiliarobjectsoreventstobeconstantlyconjoinedtogether；whatistheconsequenceofthisexperience？Heimmediatelyinferstheexistenceofoneobjectfromtheappearanceoftheother。Yethehasnot，byallhisexperience，acquiredanyideaorknowledgeofthesecretpowerbywhichtheoneobjectproducestheother；norisitbyanyprocessofreasoning，heisengagedtodrawthisinference。Butstillhefindshimselfdeterminedtodrawit:
　　Andthoughheshouldbeconvincedthathisunderstandinghasnopartintheoperation，hewouldneverthelesscontinueinthesamecourseofthinking。Thereissomeotherprinciplewhichdetermineshimtoformsuchaconclusion。
　　ThisprincipleisC/USTOM\orH/ABIT\。Forwherevertherepetitionofanyparticularactoroperationproducesapropensitytorenewthesameactoroperation，withoutbeingimpelledbyanyreasoningorprocessoftheunderstanding，wealwayssay，thatthispropensityistheeffectof。Byemployingthatword，wepretendnottohavegiventheultimatereasonofsuchapropensity。Weonlypointoutaprincipleofhumannature，whichisuniversallyacknowledged，andwhichiswellknownbyitseffects。
　　Perhapswecanpushourenquiriesnofarther，orpretendtogivethecauseofthiscause；butmustrestcontentedwithitastheultimateprinciple，whichwecanassign，ofallourconclusionsfromexperience。Itissufficientsatisfaction，thatwecangosofar，withoutrepiningatthenarrownessofourfacultiesbecausetheywillcarryusnofarther。Anditiscertainwehereadvanceaveryintelligiblepropositionatleast，ifnotatrueone，whenweassertthat，aftertheconstantconjunctionoftwoobjects——heatandflame，forinstance，weightandsolidity——wearedeterminedbycustomalonetoexpecttheonefromtheappearanceoftheother。Thishypothesisseemseventheonlyonewhichexplainsthedifficulty，whywedraw，fromathousandinstances，aninferencewhichwearenotabletodrawfromoneinstance，thatis，innorespect，differentfromthem。Reasonisincapableofanysuchvariation。Theconclusionswhichitdrawsfromconsideringonecirclearethesamewhichitwouldformuponsurveyingallthecirclesintheuniverse。Butnoman，havingseenonlyonebodymoveafterbeingimpelledbyanother，couldinferthateveryotherbodywillmoveafteralikeimpulse。
　　Allinferencesfromexperience，therefore，areeffectsofcustom，notofreasoning。[12]
　　Custom，then，isthegreatguideofhumanlife。Itisthatprinciplealonewhichrendersourexperienceusefultous，andmakesusexpect，forthefuture，asimilartrainofeventswiththosewhichhaveappearedinthepast。Withouttheinfluenceofcustom，weshouldbeentirelyignorantofeverymatteroffactbeyondwhatisimmediatelypresenttothememoryandsenses。Weshouldneverknowhowtoadjustmeanstoends，ortoemployournaturalpowersintheproductionofanyeffect。Therewouldbeanendatonceofallaction，aswellasofthechiefpartofspeculation。
　　Buthereitmaybepropertoremark，thatthoughourconclusionsfromexperiencecarryusbeyondourmemoryandsenses，andassureusofmattersoffactwhichhappenedinthemostdistantplacesandmostremoteages，yetsomefactmustalwaysbepresenttothesensesormemory，fromwhichwemayfirstproceedindrawingtheseconclusions。Aman，whoshouldfindinadesertcountrytheremainsofpompousbuildings，wouldconcludethatthecountryhad，inancienttimes，beencultivatedbycivilizedinhabitants；butdidnothingofthisnatureoccurtohim，hecouldneverformsuchaninference。Welearntheeventsofformeragesfromhistory；butthenwemustperusethevolumesinwhichthisinstructioniscontained，andthencecarryupourinferencesfromonetestimonytoanother，tillwearriveattheeyewitnessesandspectatorsofthesedistantevents。Inaword，ifweproceednotuponsomefact，presenttothememoryorsenses，ourreasoningswouldbemerelyhypothetical；andhowevertheparticularlinksmightbeconnectedwitheachother，thewholechainofinferenceswouldhavenothingtosupportit，norcouldweever，byitsmeans，arriveattheknowledgeofanyrealexistence。IfI
　　askwhyyoubelieveanyparticularmatteroffact，whichyourelate，youmusttellmesomereason；andthisreasonwillbesomeotherfact，connectedwithit。Butasyoucannotproceedafterthismanner，，youmustatlastterminateinsomefact，whichispresenttoyourmemoryorsenses；ormustallowthatyourbeliefisentirelywithoutfoundation。
　　What，then，istheconclusionofthewholematter？A
　　simpleone；though，itmustbeconfessed，prettyremotefromthecommontheoriesofphilosophy。Allbeliefofmatteroffactorrealexistenceisderivedmerelyfromsomeobject，presenttothememoryorsenses，andacustomaryconjunctionbetweenthatandsomeotherobject。Orinotherwords；
　　havingfound，inmanyinstances，thatanytwokindsofobjects——flameandheat，snowandcold——havealwaysbeenconjoinedtogether；ifflameorsnowbepresentedanewtothesenses，themindiscarriedbycustomtoexpectheatorcold，andtothatsuchaqualitydoesexist，andwilldiscoveritselfuponanearerapproach。Thisbeliefisthenecessaryresultofplacingthemindinsuchcircumstances。Itisanoperationofthesoul，whenwearesosituated，asunavoidableastofeelthepassionoflove，whenwereceivebenefits；orhatred，whenwemeetwithinjuries。Alltheseoperationsareaspeciesofnaturalinstincts，whichnoreasoningorprocessofthethoughtandunderstandingisableeithertoproduceortoprevent。
　　Atthispoint，itwouldbeveryallowableforustostopourphilosophicalresearches。Inmost
　　questionswecannevermakeasinglestepfarther；andinallquestionswemustterminatehereatlast，afterourmostrestlessandcuriousenquiries。Butstillourcuriositywillbepardonable，perhapscommendable，ifitcarryusontostillfartherresearches，andmakeusexaminemoreaccuratelythenatureofthis，andofthe，whenceitisderived。Bythismeanswemaymeetwithsomeexplicationsandanalogiesthatwillgivesatisfaction；atleasttosuchaslovetheabstractsciences，andcanbeentertainedwithspeculations，which，howeveraccurate，maystillretainadegreeofdoubtanduncertainty。Astoreadersofadifferenttaste；theremainingpartofthissectionisnotcalculatedforthem，andthefollowingenquiriesmaywellbeunderstood，thoughitbeneglected。
　　PARTII。
　　N/OTHING\ismorefreethantheimaginationofman；andthoughitcannotexceedthatoriginalstockofideasfurnishedbytheinternalandexternalsenses，ithasunlimitedpowerofmixing，compounding，separating，anddividingtheseideas，inallthevarietiesoffictionandvision。Itcanfeignatrainofevents，withalltheappearanceofreality，ascribetothemaparticulartimeandplace，conceivethemasexistent，andpaintthemouttoitselfwitheverycircumstance，thatbelongstoanyhistoricalfact，whichitbelieveswiththegreatestcertainty。Wherein，therefore，consiststhedifferencebetweensuchaand？Itliesnotmerelyinanypeculiaridea，whichisannexedtosuchaconceptionascommandsourassent，andwhichiswantingtoeveryknownfiction。Forasthemindhasauthorityoverallitsideas，itcouldvoluntarilyannexthisparticularideatoanyfiction，andconsequentlybeabletobelievewhateveritpleases；contrarytowhatwefindbydailyexperience。Wecan，inourconception，jointheheadofamantothebodyofahorse；butitisnotinourpowertobelievethatsuchananimalhaseverreallyexisted。
　　Itfollows，therefore，thatthedifferencebetweenandliesinsomesentimentorfeeling，whichisannexedtothelatter，nottotheformer，andwhichdependsnotonthewill，norcanbecommandedatpleasure。
　　Itmustbeexcitedbynature，likeallothersentiments；andmustarisefromtheparticularsituation，inwhichthemindisplacedatanyparticularjuncture。Wheneveranyobjectispresentedtothememoryorsenses，itimmediately，bytheforceofcustom，carriestheimaginationtoconceivethatobject，whichisusuallyconjoinedtoit；andthisconceptionisattendedwithafeelingorsentiment，differentfromtheloosereveriesofthefancy。Inthisconsiststhewholenatureofbelief。Forasthereisnomatteroffactwhichwebelievesofirmlythatwecannotconceivethecontrary，therewouldbenodifferencebetweentheconceptionassentedtoandthatwhichisrejected，wereitnotforsomesentimentwhichdistinguishestheonefromtheother。IfIseeabilliard-ballmovingtowardanother，onasmoothtable，Icaneasilyconceiveittostopuponcontact。Thisconceptionimpliesnocontradiction；butstillitfeelsverydifferentlyfromthatconceptionbywhichI
　　representtomyselftheimpulseandthecommunicationofmotionfromoneballtoanother。
　　Werewetoattemptaofthissentiment，weshould，perhaps，finditaverydifficult，ifnotanimpossibletask；inthesamemannerasifweshouldendeavourtodefinethefeelingofcoldorpassionofanger，toacreaturewhoneverhadanyexperienceofthesesentiments。B/ELIEF\isthetrueandpropernameofthisfeeling；andnooneiseveratalosstoknowthemeaningofthatterm；becauseeverymaniseverymomentconsciousofthesentimentrepresentedbyit。Itmaynot，however，beimpropertoattemptaofthissentiment；inhopeswemay，bythatmeans，arriveatsomeanalogies，whichmayaffordamoreperfectexplicationofit。Isay，then，thatbeliefisnothingbutamorevivid，lively，forcible，firm，steadyconceptionofanobject，thanwhattheimaginationaloneiseverabletoattain。Thisvarietyofterms，whichmayseemsounphilosophical，isintendedonlytoexpressthatactofthemind，whichrendersrealities，orwhatistakenforsuch，morepresenttousthanfictions，causesthemtoweighmoreinthethought，andgivesthemasuperiorinfluence
　　onthepassionsandimagination。Providedweagreeaboutthething，itisneedlesstodisputeabouttheterms。Theimaginationhasthecommandoverallitsideas，andcanjoinandmixandvarythem，inallthewayspossible。Itmayconceivefictitiousobjectswithallthecircumstancesofplaceandtime。Itmaysetthem，inamanner，beforeoureyes，intheirtruecolours，justastheymighthaveexisted。Butasitisimpossiblethatthisfacultyofimaginationcanever，ofitself，reachbelief，itisevidentthatbeliefconsistsnotinthepeculiarnatureororderofideas，butintheoftheirconception，andintheirtothemind。Iconfess，thatitisimpossibleperfectlytoexplainthisfeelingormannerofconception。Wemaymakeuseofwordswhichexpresssomethingnearit。Butitstrueandpropername，asweobservedbefore，is；whichisatermthateveryonesufficientlyunderstandsincommonlife。Andinphilosophy，wecangonofarther
　　thanassert，thatissomethingfeltbythemind，whichdistinguishestheideasofthejudgementfromthefictionsoftheimagination。Itgivesthemmoreweightandinfluence；makesthemappearofgreaterimportance；enforcestheminthemind；andrendersthemthegoverningprincipleofouractions。Ihearatpresent，forinstance，aperson'svoice，withwhomIamacquainted；andthesoundcomesasfromthenextroom。Thisimpressionofmysensesimmediatelyconveysmythoughttotheperson，togetherwithallthesurroundingobjects。Ipaintthemouttomyselfasexistingatpresent，withthesamequalitiesandrelations，ofwhichIformerlyknewthempossessed。
　　Theseideastakefasterholdofmymindthanideasofanenchantedcastle。Theyareverydifferenttothefeeling，andhaveamuchgreaterinfluenceofeverykind，eithertogivepleasureorpain，joyorsorrow。
　　Letus，then，takeinthewholecompassofthisdoctrine，andallow，thatthesentimentofbeliefisnothingbutaconceptionmoreintenseandsteadythanwhatattendsthemerefictionsoftheimagination，andthatthis
　　ofconceptionarisesfromacustomaryconjunctionoftheobjectwithsomethingpresenttothememoryorsenses:I
　　believethatitwillnotbedifficult，uponthesesuppositions，tofindotheroperationsofthemindanalogoustoit，andtotraceupthesephenomenatoprinciplesstillmoregeneral。
　　Wehavealreadyobservedthatnaturehasestablishedconnexionsamongparticularideas，andthatnosooneroneideaoccurstoourthoughtsthanitintroducesitscorrelative，andcarriesourattentiontowardsit，byagentleandinsensiblemovement。Theseprinciplesofconnexionorassociationwehavereducedtothree，namely，，and；whicharetheonlybondsthatuniteourthoughtstogether，andbegetthatregulartrainofreflectionordiscourse，which，inagreaterorlessdegree，takesplaceamongallmankind。Nowherearisesaquestion，onwhichthesolutionofthepresentdifficultywilldepend。Doesithappen，inalltheserelations，that，whenoneoftheobjectsispresentedtothesensesormemory，themindisnotonlycarriedtotheconceptionofthecorrelative，butreachesasteadierandstrongerconceptionofitthanwhatotherwiseitwouldhavebeenabletoattain？Thisseemstobethecasewiththatbeliefwhicharisesfromtherelationofcauseandeffect。
　　Andifthecasebethesamewiththeotherrelationsorprinciplesofassociations，thismaybeestablishedasagenerallaw，whichtakesplaceinalltheoperationsofthemind。
　　Wemay，therefore，observe，asthefirstexperimenttoourpresentpurpose，that，upontheappearanceofthepictureofanabsentfriend，ourideaofhimisevidentlyenlivenedbythe，andthateverypassion，whichthatideaoccasions，whetherofjoyorsorrow，acquiresnewforceandvigour。Inproducingthiseffect，thereconcurbotharelationandapresentimpression。Wherethepicturebearshimnoresemblance，atleastwasnotintendedforhim，itneversomuchasconveysourthoughttohim:Andwhereitisabsent，aswellastheperson，thoughthemindmaypassfromthethoughtoftheonetothatoftheother，itfeelsitsideatoberatherweakenedthanenlivenedbythattransition。Wetakeapleasureinviewingthepictureofafriend，whenitissetbeforeus；butwhenitisremoved，ratherchoosetoconsiderhimdirectlythanbyreflectioninanimage，whichisequallydistantandobscure。
　　TheceremoniesoftheR/OMAN\C/ATHOLIC\religionmaybeconsideredasinstancesofthesamenature。Thedevoteesofthatsuperstitionusuallypleadinexcuseforthemummeries，withwhichtheyareupbraided，thattheyfeelthegoodeffectofthoseexternalmotions，andpostures，andactions，inenliveningtheirdevotionandquickeningtheirfervour，whichotherwisewoulddecay，ifdirectedentirelytodistantandimmaterialobjects。Weshadowouttheobjectsofourfaith，saythey，insensibletypesandimages，andrenderthemmorepresenttousbytheimmediatepresenceofthesetypes，thanitispossibleforustodomerelybyanintellectualviewandcontemplation。Sensibleobjectshavealwaysagreaterinfluenceonthefancythananyother；andthisinfluencetheyreadilyconveytothoseideastowhichtheyarerelated，andwhichtheyresemble。Ishallonlyinferfromthesepractices，andthisreasoning，thattheeffectofresemblanceinenliveningtheideasisverycommon；andasineverycasearesemblanceandapresentimpressionmustconcur，weareabundantlysuppliedwithexperimentstoprovetherealityoftheforegoingprinciple。
　　Wemayaddforcetotheseexperimentsbyothersofadifferentkind，inconsideringtheeffectsof
　　aswellasof。Itiscertainthatdistancediminishestheforceofeveryidea，andthat，uponourapproachtoanyobject；thoughitdoesnotdiscoveritselftooursenses；itoperatesuponthemindwithaninfluence，whichimitatesanimmediateimpression。Thethinkingonanyobjectreadilytransportsthemindtowhatiscontiguous；
　　butitisonlytheactualpresenceofanobject，thattransportsitwithasuperiorvivacity。WhenIamafewmilesfromhome，whateverrelatestoittouchesmemorenearlythanwhenIamtwohundredleaguesdistant；thoughevenatthatdistancethereflectingonanythingintheneighbourhoodofmyfriendsorfamilynaturallyproducesanideaofthem。Butasinthislattercase，boththeobjectsofthemindareideas；notwithstandingthereisaneasytransitionbetweenthem；thattransitionaloneisnotabletogiveasuperiorvivacitytoanyoftheideas，forwantofsomeimmediateimpression。[13]
　　Noonecandoubtbutcausationhasthesameinfluenceastheothertworelationsofresemblanceandcontiguity。
　　Superstitiouspeoplearefondofthereliquesofsaintsandholymen，forthesamereason，that
　　theyseekaftertypesorimages，inordertoenliventheirdevotion，andgivethemamoreintimateandstrongconceptionofthoseexemplarylives，whichtheydesiretoimitate。Nowitisevident，thatoneofthebestreliques，whichadevoteecouldprocure，wouldbethehandyworkofasaint；andifhiscloathsandfurnitureareevertobeconsideredinthislight，itisbecausetheywereonceathisdisposal，andweremovedandaffectedbyhim；inwhichrespecttheyaretobeconsideredasimperfecteffects，andasconnectedwithhimbyashorterchainofconsequencesthananyofthose，bywhichwelearntherealityofhisexistence。
　　Suppose，thatthesonofafriend，whohadbeenlongdeadorabsent，werepresentedtous；itisevident，thatthisobjectwouldinstantlyreviveitscorrelativeidea，andrecalltoourthoughtsallpastintimaciesandfamiliarities，inmorelivelycoloursthantheywouldotherwisehaveappearedtous。Thisisanotherphaenomenon，whichseemstoprovetheprincipleabovementioned。
　　Wemayobserve，that，inthesephaenomena，thebeliefofthecorrelativeobjectisalwayspresupposed；withoutwhichtherelationcouldhavenoeffect。Theinfluenceofthepicturesupposes，thatweourfriendtohaveonceexisted。Contiguitytohomecanneverexciteourideasofhome，unlesswethatitreallyexists。NowI
　　assert，thatthisbelief，whereitreachesbeyondthememoryorsenses，isofasimilarnature，andarisesfromsimilarcauses，withthetransitionofthoughtandvivacityofconceptionhereexplained。WhenIthrowapieceofdrywoodintoafire，mymindisimmediatelycarriedtoconceive，thatitaugments，notextinguishestheflame。Thistransitionofthoughtfromthecausetotheeffectproceedsnotfromreason。Itderivesitsoriginaltogetherfromcustomandexperience。Andasitfirstbeginsfromanobject，presenttothesenses，itrenderstheideaorconceptionofflamemore
　　strongandlivelythananyloose，floatingreverieoftheimagination。Thatideaarisesimmediately。Thethoughtmovesinstantlytowardsit，andconveystoitallthatforceofconception，whichisderivedfromtheimpressionpresenttothesenses。Whenaswordislevelledatmybreast，doesnottheideaofwoundandpainstrikememorestrongly，thanwhenaglassofwineispresentedtome，eventhoughbyaccidentthisideashouldoccuraftertheappearanceofthelatterobject？Butwhatisthereinthiswholemattertocausesuchastrongconception，exceptonlyapresentobjectandacustomarytransitionoftheideaofanotherobject，whichwehavebeenaccustomedtoconjoinwiththeformer？Thisisthewholeoperationofthemind，inallourconclusionsconcerningmatteroffactandexistence；anditisasatisfactiontofindsome
　　analogies，bywhichitmaybeexplained。Thetransitionfromapresentobjectdoesinallcasesgivestrengthandsoliditytotherelatedidea。
　　Here，then，isakindofpre-establishedharmonybetweenthecourseofnatureandthesuccessionofourideas；andthoughthepowersandforces，bywhichtheformerisgoverned，bewhollyunknowntous；yetourthoughtsandconceptionshavestill，wefind，goneoninthesametrainwiththeotherworksofnature。Customisthatprinciple，bywhichthiscorrespondencehasbeeneffected；sonecessarytothesubsistenceofourspecies，andtheregulationofourconduct，ineverycircumstanceandoccurrenceofhumanlife。
　　Hadnotthepresenceofanobject，instantlyexcitedtheideaofthoseobjects，commonlyconjoinedwithit，allourknowledgemusthavebeenlimitedtothenarrowsphereofourmemoryandsenses；andweshouldneverhavebeenabletoadjustmeanstoends，oremployournaturalpowers，eithertotheproducingofgood，oravoidingofevil。Those，whodelightinthediscoveryandcontemplationof，havehereamplesubjecttoemploytheirwonderandadmiration。
　　Ishalladd，forafurtherconfirmationoftheforegoingtheory，that，asthisoperationofthemind，bywhichweinferlikeeffectsfromlikecauses，and，issoessentialtothesubsistenceofallhumancreatures，itisnotprobable，thatitcouldbetrustedtothefallaciousdeductionsofourreason，whichisslowinitsoperations；appearsnot，inanydegree，duringthefirstyearsofinfancy；andatbestis，ineveryageandperiodofhumanlife，extremelyliabletoerrorandmistake。Itismoreconformabletotheordinarywisdomofnaturetosecuresonecessaryanactof
　　themind，bysomeinstinctormechanicaltendency，whichmaybeinfallibleinitsoperations，maydiscoveritselfatthefirstappearanceoflifeandthought，andmaybeindependentofallthelaboureddeductionsoftheunderstanding。Asnaturehastaughtustheuseofourlimbs，withoutgivingustheknowledgeofthemusclesandnerves，bywhichtheyareactuated；sohassheimplantedinusaninstinct，whichcarriesforwardthethoughtinacorrespondentcoursetothatwhichshehasestablishedamongexternalobjects；thoughweareignorantofthosepowersandforces，onwhichthisregularcourseandsuccessionofobjectstotallydepends。
　　SECTIONVI。
　　OfProbability。[14]
　　Thereiscertainlyaprobability，whicharisesfromasuperiorityofchancesonanyside；andaccordingasthissuperiorityincreases，andsurpassestheoppositechances，theprobabilityreceivesaproportionableincrease，andbegetsstillahigherdegreeofbelieforassenttothatside，inwhichwediscoverthesuperiority。Ifadyeweremarkedwithonefigureornumberofspotsonfoursides，andwithanotherfigureornumberofspotsonthetworemainingsides，itwouldbemoreprobable，thattheformerwouldturnupthanthelatter；though，ifithadathousandsidesmarkedinthesamemanner，andonlyonesidedifferent，theprobabilitywouldbemuchhigher，andourbelieforexpectationoftheeventmoresteadyandsecure。Thisprocessofthethoughtorreasoningmayseemtrivialandobvious；buttothosewhoconsideritmorenarrowly，itmay，perhaps，affordmatterforcuriousspeculation。
　　Itseemsevident，that，whenthemindlooksforwardtodiscovertheevent，whichmayresultfromthethrowofsuchadye，itconsiderstheturningupofeachparticularsideasalikeprobable；andthisistheverynatureofchance，torenderalltheparticularevents，comprehendedinit，entirelyequal。Butfindingagreaternumberofsidesconcurintheoneeventthanintheother，themindiscarriedmorefrequentlytothatevent，andmeetsitoftener，inrevolvingthevariouspossibilitiesorchances，onwhichtheultimateresultdepends。Thisconcurrenceofseveralviewsinoneparticulareventbegetsimmediately，byaninexplicablecontrivanceofnature，thesentimentofbelief，andgivesthateventtheadvantageoveritsantagonist，whichissupportedbyasmallernumberofviews，andrecurslessfrequentlytothemind。Ifweallow，thatbeliefisnothingbutafirmerandstrongerconceptionofanobjectthanwhatattendsthemerefictionsoftheimagination，thisoperationmay，perhaps，insomemeasure，beaccountedfor。Theconcurrenceoftheseseveralviewsorglimpses
　　imprintstheideamorestronglyontheimagination；givesitsuperiorforceandvigour；rendersitsinfluenceonthepassionsandaffectionsmoresensible；andinaword，begetsthatrelianceorsecurity，whichconstitutesthenatureofbeliefandopinion。
　　Thecaseisthesamewiththeprobabilityofcauses，aswiththatofchance。Therearesomecauses，whichareentirelyuniformandconstantinproducingaparticulareffect；andnoinstancehaseveryetbeenfoundofanyfailureorirregularityintheiroperation。Firehasalwaysburned，andwatersuffocatedeveryhumancreature:Theproductionofmotionbyimpulseandgravityisanuniversallaw，whichhashithertoadmittedofnoexception。Butthereareothercauses，whichhavebeenfoundmoreirregularanduncertain；norhasrhubarbalwaysprovedapurge，oropiumasoporifictoeveryone，whohastakenthesemedicines。Itistrue，whenanycausefailsofproducingitsusualeffect，philosophersascribenotthistoanyirregularityinnature；
　　butsuppose，thatsomesecretcauses，intheparticularstructureofparts，havepreventedtheoperation。Ourreasonings，however，andconclusionsconcerningtheeventarethesameasifthisprinciplehadnoplace。Beingdeterminedbycustomtotransferthepasttothefuture，inallourinferences；wherethepasthasbeenentirelyregularanduniform，weexpecttheeventwiththegreatestassurance，andleavenoroomforanycontrarysupposition。
　　Butwheredifferenteffectshavebeenfoundtofollowfromcauses，whicharetoexactlysimilar，allthesevariouseffectsmustoccurtothemindintransferringthepasttothefuture，andenterintoourconsideration，whenwedeterminetheprobabilityoftheevent。Thoughwegivethepreferencetothatwhichhasbeenfoundmostusual，andbelievethatthiseffectwillexist，wemustnotoverlooktheothereffects，butmustassigntoeachofthemaparticularweightandauthority，inproportionaswehavefoundittobemoreorlessfrequent。Itismoreprobable，inalmosteverycountryofE/UROPE\，thattherewillbefrostsometimeinJ/ANUARY\，thanthattheweatherwillcontinueopenthroughoutthatwholemonth；thoughthisprobabilityvariesaccordingtothedifferentclimates，andapproachestoacertaintyinthemorenorthernkingdoms。
　　Herethenitseemsevident，that，whenwetransferthepasttothefuture，inordertodeterminetheeffect，whichwillresultfromanycause，wetransferallthedifferentevents，inthesameproportionastheyhaveappearedinthepast，andconceiveonetohaveexistedahundredtimes，forinstance，anothertentimes，andanotheronce。Asagreatnumberofviewsdohereconcurinoneevent，theyfortifyandconfirmittotheimagination，begetthatsentimentwhichwecall，andgiveitsobjectthepreferenceabovethecontraryevent，whichisnotsupportedbyanequalnumberofexperiments，andrecursnotsofrequentlytothethoughtintransferringthepasttothefuture。Letanyonetrytoaccountforthisoperationoftheminduponanyofthereceivedsystemsofphilosophy，andhewillbesensibleofthedifficulty。Formypart，Ishallthinkitsufficient，ifthepresenthintsexcitethecuriosityofphilosophers，andmakethemsensiblehowdefectiveallcommontheoriesareintreatingofsuchcuriousandsuchsublimesubjects。
　　SECTIONVII。
　　OftheIdeaofNecessaryConnexion。
　　PARTI。
　　T/HE\greatadvantageofthemathematicalsciencesabovethemoralconsistsinthis，thattheideasoftheformer，beingsensible，arealwaysclearanddeterminate，thesmallestdistinctionbetweenthemisimmediatelyperceptible，andthesametermsarestillexpressiveofthesameideas，withoutambiguityorvariation。Anovalisnevermistakenforacircle，noranhyperbolaforanellipsis。Theisoscelesandscalenumaredistinguishedbyboundariesmoreexactthanviceandvirtue，rightandwrong。Ifanytermbedefinedingeometry，themindreadily，ofitself，substitutes，onalloccasions，thedefinitionforthetermdefined:Orevenwhennodefinitionisemployed，theobjectitselfmaybepresentedtothesenses，andbythatmeansbesteadilyandclearlyapprehended。Butthefinersentimentsofthemind，theoperationsoftheunderstanding，thevariousagitationsofthepassions，thoughreallyinthemselvesdistinct，easilyescapeus，whensurveyedbyreflection；norisitinourpowertorecalltheoriginalobject，asoftenaswehaveoccasiontocontemplateit。
　　Ambiguity，bythismeans，isgraduallyintroducedintoourreasonings:Similarobjectsarereadilytakentobethesame:Andtheconclusionbecomesatlastverywideofthepremises。
　　Onemaysafely，however，affirm，that，ifweconsiderthesesciencesinaproperlight，theiradvantagesanddisadvantagesnearlycompensateeachother，andreducebothofthemtoastateofequality。Ifthemind，withgreaterfacility，retainstheideasofgeometryclearanddeterminate，itmustcarryonamuchlongerandmoreintricatechainofreasoning，andcompareideasmuchwiderofeachother，inordertoreachtheabstrusertruthsofthatscience。Andifmoralideasareapt，withoutextremecare，tofallintoobscurityandconfusion，theinferencesarealwaysmuchshorterinthesedisquisitions，andtheintermediatesteps，whichleadtotheconclusion，muchfewerthaninthescienceswhichtreatofquantityandnumber。Inreality，thereisscarcelyapropositioninE/UCLID\sosimple，asnottoconsistofmoreparts，thanaretobefoundinanymoralreasoningwhichrunsnotintochimeraandconceit。Wherewetracetheprinciplesofthehuman
　　mindthroughafewsteps，wemaybeverywellsatisfiedwithourprogress；consideringhowsoonnaturethrowsabartoallourenquiriesconcerningcauses，andreducesustoanacknowledgmentofourignorance。Thechiefobstacle，therefore，toourimprovementinthemoralormetaphysicalsciencesistheobscurityoftheideas，andambiguityoftheterms。Theprincipaldifficultyinthemathematicsisthelengthofinferencesandcompassofthought，requisitetotheformingofanyconclusion。And，perhaps，ourprogressinnaturalphilosophyischieflyretardedbythewantofproperexperimentsandphaenomena，whichareoftendiscoveredbychance，andcannotalwaysbefound，whenrequisite，evenbythemostdiligentandprudentenquiry。Asmoralphilosophyseemshithertotohavereceivedlessimprovementthaneithergeometryorphysics，wemayconclude，that，iftherebeanydifferenceinthisrespectamongthesesciences，thedifficulties，whichobstructtheprogressoftheformer，requiresuperiorcareandcapacitytobesurmounted。
　　Therearenoideas，whichoccurinmetaphysics，moreobscureanduncertain，thanthoseof，，or，ofwhichitiseverymomentnecessaryforustotreatinallourdisquisitions。
　　Weshall，therefore，endeavour，inthissection，tofix，ifpossible，theprecisemeaningoftheseterms，andtherebyremovesomepartofthatobscurity，whichissomuchcomplainedofinthisspeciesofphilosophy。
　　Itseemsaproposition，whichwillnotadmitofmuchdispute，thatallourideasarenothingbutcopiesofourimpressions，or，inotherwords，thatitisimpossibleforustoofanything，whichwehavenotantecedently，eitherbyourexternalorinternalsenses。Ihaveendeavoured[15]toexplainandprovethisproposition，andhaveexpressedmyhopes，that，byaproperapplicationofit，menmayreachagreaterclearnessandprecisioninphilosophicalreasonings，thanwhattheyhavehithertobeenabletoattain。Complexideas，may，perhaps，bewellknownbydefinition，whichisnothingbutanenumerationofthosepartsorsimpleideas，thatcomposethem。Butwhenwehavepushedupdefinitionstothemostsimpleideas，andfindstillmoreambiguityandobscurity；whatresourcearewethenpossessedof？Bywhat
　　inventioncanwethrowlightupontheseideas，andrenderthemaltogetherpreciseanddeterminatetoourintellectualview？Producetheimpressionsororiginalsentiments，fromwhichtheideasarecopied。Theseimpressionsareallstrongandsensible。Theyadmitnotofambiguity。Theyarenotonlyplacedinafulllightthemselves，butmaythrowlightontheircorrespondentideas，whichlieinobscurity。Andbythismeans，wemay，perhaps，attainanewmicroscopeorspeciesofoptics，bywhich，inthemoralsciences，themostminute，andmostsimpleideasmaybesoenlargedastofallreadilyunderourapprehension，andbeequallyknownwiththegrossestandmostsensibleideas，thatcanbetheobjectofourenquiry。
　　Tobefullyacquainted，therefore，withtheideaofpowerornecessaryconnexion，letusexamineitsimpression；
　　andinordertofindtheimpressionwithgreatercertainty，letussearchforitinallthesources，fromwhichitmaypossiblybederived。
　　Whenwelookaboutustowardsexternalobjects，andconsidertheoperationofcauses，weareneverable，inasingleinstance，todiscoveranypowerornecessaryconnexion；anyquality，whichbindstheeffecttothecause，andrenderstheoneaninfallibleconsequenceoftheother。
　　Weonlyfind，thattheonedoesactually，infact，followtheother。Theimpulseofonebilliard-ballisattendedwithmotioninthesecond。Thisisthewholethatappearstothesenses。Themindfeelsnosentimentorimpressionfromthissuccessionofobjects:
　　Consequently，thereisnot，inanysingle，particularinstanceofcauseandeffect，anythingwhichcansuggesttheideaofpowerornecessaryconnexion。
　　Fromthefirstappearanceofanobject，wenevercanconjecturewhateffectwillresultfromit。Butwerethepowerorenergyofanycausediscoverablebythemind，wecouldforeseetheeffect，evenwithoutexperience；andmight，atfirst，pronouncewithcertaintyconcerningit，bymeredintofthoughtandreasoning。
　　Inreality，thereisnopartofmatter，thatdoesever，byitssensiblequalities，discoveranypowerorenergy，orgiveusgroundtoimagine，thatitcouldproduceanything，orbefollowedbyanyotherobject，whichwecoulddenominateitseffect。Solidity，extension，motion；thesequalitiesareallcompleteinthemselves，andneverpointoutanyothereventwhichmayresultfromthem。Thescenesoftheuniversearecontinuallyshifting，andoneobjectfollowsanotherinanuninterruptedsuccession；butthepowerofforce，whichactuatesthewholemachine，isentirelyconcealedfromus，andneverdiscoversitselfinanyofthesensiblequalitiesofbody。Weknowthat，infact，heatisaconstantattendantofflame；butwhatistheconnexionbetweenthem，wehavenoroomsomuchastoconjectureorimagine。Itisimpossible，therefore，thattheideaofpowercanbederivedfromthecontemplationofbodies，insingleinstancesoftheiroperation；becausenobodieseverdiscoveranypower，whichcanbetheoriginalofthisidea。[16]
　　Since，therefore，externalobjectsastheyappeartothesenses，giveusnoideaofpowerornecessaryconnexion，bytheiroperationinparticularinstances，letussee，whetherthisideabederivedfromreflectionontheoperationsofourownminds，andbecopiedfromanyinternalimpression。Itmaybesaid，thatweareeverymomentconsciousofinternalpower；whilewefeel，that，bythesimplecommandofourwill，wecanmovetheorgansofourbody，ordirectthefacultiesofourmind。Anactofvolitionproducesmotioninourlimbs，orraisesanewideainourimagination。Thisinfluenceofthewillweknowbyconsciousness。Henceweacquiretheideaofpowerorenergy；
　　andarecertain，thatweourselvesandallotherintelligentbeingsarepossessedofpower。Thisidea，then，isanideaofreflection，sinceitarisesfromreflectingontheoperationsofourownmind，andonthecommandwhichisexercisedbywill，bothovertheorgansofthebodyandfacultiesofthesoul。
　　Weshallproceedtoexaminethispretension；andfirstwithregardtotheinfluenceofvolitionovertheorgansofthebody。Thisinfluence，wemayobserve，isafact，which，likeallothernaturalevents，canbeknownonlybyexperience，andcanneverbeforeseenfromanyapparentenergyorpowerinthecause，whichconnectsitwiththeeffect，andrenderstheoneaninfallibleconsequenceoftheother。Themotionofourbodyfollowsuponthecommandofourwill。Ofthisweareeverymomentconscious。Butthemeans，bywhichthisiseffected；theenergy，bywhichthewillperformssoextraordinaryanoperation；ofthiswearesofarfrombeingimmediatelyconscious，thatitmustforeverescapeourmostdiligent
　　enquiry。
　　For；isthereanyprincipleinallnaturemoremysteriousthantheunionofsoulwithbody；bywhichasupposedspiritualsubstanceacquiressuchaninfluenceoveramaterialone，thatthemostrefinedthoughtisabletoactuatethegrossestmatter？Wereweempowered，byasecretwish，toremovemountains，orcontroltheplanetsintheirorbit；thisextensiveauthoritywouldnotbemoreextraordinary，normorebeyondourcomprehension。Butifbyconsciousnessweperceivedanypowerorenergyinthewill，wemustknowthispower；wemustknowitsconnexionwiththeeffect；wemustknowthesecretunionofsoulandbody，andthenatureofboththesesubstances；bywhichtheoneisabletooperate，insomanyinstances，upontheother。
　　，Wearenotabletomovealltheorgansofthebodywithalikeauthority；thoughwecannotassignanyreasonbesidesexperience，forsoremarkableadifferencebetweenoneandtheother。Whyhasthewillaninfluenceoverthetongueandfingers，notovertheheartorliver？
　　Thisquestionwouldneverembarrassus，wereweconsciousofapowerintheformercase，notinthelatter。Weshouldthenperceive，independentofexperience，whytheauthorityofwillovertheorgansofthebodyiscircumscribedwithinsuchparticularlimits。Beinginthatcasefullyacquaintedwiththepowerorforce，bywhichitoperates，weshouldalsoknow，whyitsinfluencereachespreciselytosuchboundaries，andnofarther。
　　Aman，suddenlystruckwithpalsyinthelegorarm，orwhohadnewlylostthosemembers，frequentlyendeavours，atfirsttomovethem，andemploythem，intheirusualoffices。
　　Hereheisasmuchconsciousofpowertocommandsuchlimbs，asamaninperfecthealthisconsciousofpowertoactuateanymemberwhichremainsinitsnaturalstateandcondition。
　　Butconsciousnessneverdeceives。Consequently，neitherintheonecasenorintheother，areweeverconsciousofanypower。Welearntheinfluenceofourwillfromexperiencealone。Andexperienceonlyteachesus，howoneeventconstantlyfollowsanother；withoutinstructingusinthesecretconnexion，whichbindsthemtogether，andrenderstheminseparable。
　　，Welearnfromanatomy，thattheimmediateobjectofpowerinvoluntarymotion，isnotthememberitselfwhichismoved，butcertainmuscles，andnerves，andanimalspirits，and，perhaps，somethingstillmoreminuteandmoreunknown，throughwhichthemotionissuccessivelypropagated，ereitreachthememberitselfwhosemotionistheimmediateobjectofvolition。Cantherebeamorecertainproof，thatthepower，bywhichthiswholeoperationisperformed，sofarfrombeingdirectlyandfullyknownbyaninwardsentimentorconsciousnessis，tothelastdegree，mysteriousandunintelligible？Herethemindwillsacertainevent。Immediatelyanotherevent，unknowntoourselves，andtotallydifferentfromtheoneintended，isproduced:Thiseventproducesanother，equallyunknown:Tillatlast，throughalongsuccession，thedesiredeventisproduced。
　　Butiftheoriginalpowerwerefelt，itmustbeknown:Wereitknown，itseffectalsomustbeknown；sinceallpowerisrelativetoitseffect。And，iftheeffectbenotknown，thepowercannotbeknownnorfelt。Howindeedcanwebeconsciousofapowertomoveourlimbs，whenwehavenosuchpower；butonlythattomovecertainanimalspirits，which，thoughtheyproduceatlastthemotionofourlimbs，yetoperateinsuchamannerasiswhollybeyondourcomprehension？
　　Wemay，therefore，concludefromthewhole，Ihope，withoutanytemerity，thoughwithassurance；thatourideaofpowerisnotcopiedfromanysentimentorconsciousnessofpowerwithinourselves，whenwegiverisetoanimalmotion，orapplyourlimbstotheirproperuseandoffice。
　　Thattheirmotionfollowsthecommandofthewillisamatterofcommonexperience，likeothernaturalevents:Butthepowerorenergybywhichthisiseffected，likethatinothernaturalevents，isunknownandinconceivable。[17]
　　Shallwethenassert，thatweareconsciousofapowerorenergyinourownminds，when，byanactorcommandofourwill，weraiseupanewidea，fixthemindtothecontemplationofit，turnitonallsides，andatlastdismissitforsomeotheridea，whenwethinkthatwehavesurveyeditwithsufficientaccuracy？Ibelievethesameargumentswillprove，thateventhiscommandofthewillgivesusnorealideaofforceorenergy。
　　，Itmustbeallowed，that，whenweknowapower，weknowthatverycircumstanceinthecause，bywhichitisenabledtoproducetheeffect:Forthesearesupposedtobesynonymous。Wemust，therefore，knowboththecauseandeffect，andtherelationbetweenthem。Butdowepretendtobeacquaintedwiththenatureofthehumansoulandthenatureofanidea，ortheaptitudeoftheonetoproducetheother？Thisisarealcreation；aproductionofsomethingoutofnothing:Whichimpliesapowersogreat，thatitmayseem，atfirstsight，beyondthereachofanybeing，lessthaninfinite。Atleastitmustbeowned，thatsuchapowerisnotfelt，norknown，norevenconceivablebythemind。Weonlyfeeltheevent，namely，theexistenceofanidea，consequenttoacommandofthewill:Butthemanner，inwhichthisoperationisperformed，thepowerbywhichitisproduced，isentirelybeyondourcomprehension。
　　，Thecommandofthemindoveritselfislimited，aswellasitscommandoverthebody；andtheselimitsarenotknownbyreason，oranyacquaintancewiththenatureofcauseandeffect，butonlybyexperienceandobservation，asinallothernaturaleventsandintheoperationofexternalobjects。Ourauthorityoveroursentimentsandpassionsismuchweakerthanthatoverourideas；andeventhelatterauthorityiscircumscribedwithinverynarrowboundaries。Willanyonepretendtoassigntheultimatereasonoftheseboundaries，orshowwhythepowerisdeficientinonecase，notinanother。