OfProbability；andoftheIdeaofCauseandEffect。
　　ThisisallIthinknecessarytoobserveconcerningthosefourrelations，whicharethefoundationofscience；butastotheotherthree，whichdependnotupontheidea，andmaybeabsentorpresentevenwhilethatremainsthesame，’twillbepropertoexplainthemmoreparticularly。Thesethreerelationsareidentity，thesituationsintimeandplace，andcausation。
　　Allkindsofreasoningconsistinnothingbutacomparison，andadiscoveryofthoserelations，eitherconstantorinconstant，whichtwoormoreobjectsbeartoeachother。Thiscomparisonwemaymake，eitherwhenboththeobjectsarepresenttothesenses，orwhenneitherofthemispresent，orwhenonlyone。Whenboththeobjectsarepresenttothesensesalongwiththerelation，wecallthisperceptionratherthanreasoning；noristhereinthiscaseanyexerciseofthethought，oranyaction，properlyspeaking，butamerepassiveadmissionoftheimpressionsthro’theorgansofsensation。’Accordingtothiswayofthinking，weoughtnottoreceiveasreasoninganyoftheobservationswemaymakeconcerningidentity，andtherelationsoftimeand。place；sinceinnoneofthemthemindcangobeyondwhatisimmediatelypresenttothesenses，eithertodiscovertherealexistenceortherelationsofobjects。’Tisonlycausation，whichproducessuchaconnexion，astogiveusassurancefromtheexistenceoractionofoneobject，that’twasfollow’dorprecededbyanyotherexistenceoraction；norcantheothertworelationsbeevermadeuseofinreasoning，exceptsofarastheyeitheraffectorareaffectedbyit。Thereisnothinginanyobjectstoperswadeus，thattheyareeitheralwaysremoteoralwayscontiguous；andwhenfromexperienceandobservationwediscover，thattheirrelationinthisparticularisinvariable，we，alwaysconcludethereissomesecretcause，whichseparatesorunitesthem。Thesamereasoningextendstoidentity。Wereadilysupposeanobjectmaycontinueindividuallythesame，tho’severaltimesabsentfromandpresenttothesenses；andascribetoitanidentity，notwithstandingtheinterruptionoftheperception，wheneverweconclude，thatifwehadkeptoureyeorhandconstantlyuponit，itwou’dhaveconvey’daninvariableanduninterruptedperception。Butthisconclusionbeyondtheimpressionsofoursensescanbefoundedonlyontheconnexionofcauseandeffect；norcanweotherwisehaveanysecurity，thattheobjectisnotchang’duponus，howevermuchthenewobjectmayresemblethatwhichwasformerlypresenttothesenses。"Wheneverwediscoversuchaperfectresemblance，weconsider，whetheritbecommoninthatspeciesofobjects；whetherpossiblyorprobablyanycausecou’doperateinproducingthechangeandresemblance；andaccordingaswedetermineconcerningthesecausesandeffects，weformourjudgmentconcerningtheidentityoftheobject。
　　Herethenitappears，thatofthosethreerelations，whichdependnotuponthemereideas，theonlyone，thatcanbetrac’dbeyondoursenses’andinformsusofexistencesandobjects，whichwedonotseeorfeel，iscausation。Thisrelation，therefore，weshallendeavourtoexplainfullybeforeweleavethesubjectoftheunderstanding。
　　Tobeginregularly，wemustconsidertheideaofcausation，andseefromwhatoriginitisderiv’d。’Tisimpossibletoreasonjustly，withoutunderstandingperfectlytheideaconcerningwhichwereason；and’tisimpossibleperfectlytounderstandanyidea，withouttracingituptoitsorigin，andexaminingthatprimaryimpression，fromwhichitarises。Theexaminationoftheimpressionbestowsaclearnessontheidea；andtheexaminationoftheideabestowsalikeclearnessonallourreasoning。
　　Letusthereforecastoureyeonanytwoobjects，whichwe-，allcauseandeffect，andturnthemonallsides，inordertofindthatimpression，whichproducesanidea，ofsuchprodigiousconsequence。AtfirstsightIperceive，thatImustnotsearchforitinanyoftheparticularqualitiesoftheobjects；since。which-everofthesequalitiesIpitchon，Ifindsomeobject，thatisnotposse。tofit，andyetfallsunderthedenominationofcauseoreffect。Andindeedthereisnothingexistent，eitherexternallyorinternally，whichisnottobeconsideredeitherasacauseoraneffect；tho’’tisplainthereisnoonequality，whichuniversallybelongstoallbeings，andgivesthematitletothatdenomination。
　　Theidea，then，ofcausationmustbederiv’dfromsome，relationamongobjects；andthatrelationwemustnowendeavourtodiscover。Ifindinthefirstplace，thatwhateverobjectsareconsideredascausesoreffects，arecontiguous；andthatnothingcanoperateinatimeorplace，whichiseversolittleremov’dfromthoseofitsexistence。Tho’distantobjectsmaysometimesseemproductiveofeachother，theyarecommonlyfounduponexaminationtobelink’dbyachainofcauses，whicharecontiguousamongthemselves，andtothedistantobjects；andwheninanyparticularinstancewecannotdiscoverthisconnexion，westillpresumeittoexist。WemaythereforeconsidertherelationofCONTIGUITYasessentialtothatofcausation；atleastmaysupposeitsuch，accordingtothegeneralopinion，tillwecanfindamore15properoccasiontoclearupthismatter，byexaminingwhatobjectsareorarenotsusceptibleofjuxtapositionandconjunction。
　　ThesecondrelationIshallobserveasessentialtocausesandeffects，isnotsouniversallyacknowledged，butisliabletosomecontroversy。’TisthatofPRIORITYOftimeinthecausebeforetheeffect。Somepretendthat’tisnotabsolutelynecessaryacauseshou’dprecedeitseffect；butthatanyobjectoraction，intheveryfirstmomentofitsexistence，mayexertitsproductivequality，andgiverisetoanotherobjectoraction，perfectlyco-temporarywithitself。Butbesidethatexperienceinmostinstancesseemstocontradictthisopinion，wemayestablishtherelationofprioritybyakindofinferenceorreasoning。’Tisanestablishedmaximbothinnaturalandmoralphilosophy，thatanobject，whichexistsforanytimeinitsfullperfectionwithoutproducinganother，isnotitssolecause；butisassistedbysomeotherprinciple，whichpushesitfromitsstateofinactivity，andmakesitexertthatenergy，ofwhichitwassecretlypossest。Nowifanycausemaybeperfectlyco-temporarywithitseffect，’tiscertain，accordingtothismaxim，thattheymustallofthembeso；sinceanyoneofthem，whichretardsitsoperationforasinglemoment，exertsnotitselfatthatveryindividualtime，inwhichitmighthaveoperated；andthereforeisnopropercause。Theconsequenceofthiswou’dbenolessthanthedestructionofthatsuccessionofcauses，whichweobserveintheworld；andindeed，theutterannihilationoftime。Forifonecausewereco-temporarywithitseffect，andthiseffectwithitseffect，andsoon，’tisplaintherewou’dbenosuchthingassuccession，andallobjectsmustbeco-existent。
　　Ifthisargumentappearsatisfactory，’tiswell。Ifnot，Ibegthereadertoallowmethesameliberty，whichIhaveus’dintheprecedingcase，ofsupposingitsuch。Forheshallfind，thattheaffairisofnogreatimportance。
　　Havingthusdiscoveredorsuppos’dthetworelationsofcontiguityandsuccessiontobeessentialtocausesandeffects，IfindIamstoptshort，andcanproceednofartherinconsideringanysingleinstanceofcauseandeffect。Motioninonebodyisregardeduponimpulseasthecauseofmotioninanother。Whenweconsidertheseobjectswithutmostattention，wefindonlythattheonebodyapproachestheother；andthatthemotionofitprecedesthatoftheother，butwithoutany，sensibleinterval。’Tisinvaintorackourselveswithfartherthoughtandreflectionuponthissubject。Wecangonofartherinconsideringthisparticularinstance。
　　Shou’danyoneleavethisinstance，andpretendtodefineacause，bysayingitissomethingproductiveofanother，’tisevidenthewou’dsaynothing。Forwhatdoeshemeanbyproduction？Canhegiveanydefinitionofit，thatwillnotbethesamewiththatofcausation？Ifhecan；Idesireitmaybeproduc’d。Ifhecannot；hehererunsinacircle，andgivesasynonimousterminsteadofadefinition。
　　Shallwethenrestcontentedwiththesetworelationsofcontiguityandsuccession，asaffordingacompleteideaofcausation？By，nomeans。Anobjectmaybecontiguousandpriortoanother，withoutbeingconsideredasitscause。ThereisaNECESSARYCONNEXIONtobetakenintoconsideration；andthatrelationisofmuchgreaterimportance，thananyoftheothertwoabove-mention’d。
　　HereagainIturntheobjectonallsides，inordertodiscoverthenatureofthisnecessaryconnexion，andfindtheimpression，orimpressions，fromwhichitsideamaybederiv’d。WhenIcastmyeyeontheknownQualitiesofobjects，Iimmediatelydiscoverthattherelationofcauseandeffectdependsnotintheleastonthem。WhenIconsidertheirrelations，Icanfindnonebutthoseofcontiguityandsuccession；whichIhavealreadyregardedasimperfectandunsatisfactory。Shallthedespairofsuccessmakemeassert，thatIamherepossestofanidea，whichisnotprecededbyanysimilarimpression？Thiswou’dbetoostrongaproofoflevityandinconstancy；sincethecontraryprinciplehasbeenalreadysofirmlyestablished，astoadmitofnofartherdoubt；atleast，tillwehavemorefullyexamin’dthepresentdifficulty。
　　Wemust，，therefore，proceedlikethose，whobeinginsearchofanything，thatliesconceal’dfromthem，andnotfindingitintheplacetheyexpected，beataboutalltheneighbouringfields，withoutanycertainviewordesign，inhopestheirgoodfortunewillatlastguidethemtowhattheysearchfor。’Tisnecessaryforustoleavethedirectsurveyofthisquestionconcerningthenatureofthatnecessaryconnexion，whichentersintoourideaofcauseandeffect；andendeavourtofindsomeotherquestions，theexaminationofwhichwillperhapsaffordahint，thatmayservetoclearupthepresentdifficulty。Ofthesequestionsthereoccurtwo，whichIshallproceedtoexamine，viz。
　　First，Forwhatreasonwepronounceitnecessary，thateverythingwhoseexistencehasabeginning，shou’dalsohaveacause。
　　Secondly，Whyweconclude，thatsuchparticularcausesmustnecessarilyhavesuchparticulareffects；andwhatisthenatureofthatinferencewedrawfromtheonetotheother，andofthebeliefwereposeinit？
　　IshallonlyobservebeforeIproceedanyfarther，thattho’theideasofcauseandeffectbederiv’dfromtheimpressionsofreflectionaswellasfromthoseofsensation，yetforbrevity’ssake，Icommonlymentiononlythelatterastheoriginoftheseideas；tho’IdesirethatwhateverIsayofthemmayalsoextendtotheformer。Passionsareconnectedwiththeirobjectsandwithoneanother；nolessthanexternalbodiesareconnectedtogether。Thesamerelation，then，ofcauseandeffect，whichbelongstoone，mustbecommontoallofthem。
　　WhyaCauseisalwaysNecessary。
　　Tobeginwiththefirstquestionconcerningthenecessityofacause:’Tisageneralmaximinphilosophy，thatwhateverbeginstoexist，musthaveacauseofexistence。Thisiscommonlytakenforgrantedinallreasonings，withoutanyproofgivenordemanded。’Tissuppos’dtobefoundedonintuition，andtobeoneofthosemaxims，whichtho’theymaybedeny’dwiththelips，’tisimpossibleformenintheirheartsreallytodoubtof。Butifweexaminethismaximbytheideaofknowledgeabove-explain’d，weshalldiscoverinitnomarkofanysuchintuitivecertainty；butonthecontraryshallfind，that’tisofanaturequiteforeigntothatspeciesofconviction。
　　Allcertaintyarisesfromthecomparisonofideas，andfromthediscoveryofsuchrelationsasareunalterable，solongastheideascontinuethesame。Theserelationsareresemblance，proportionsinquantityandnumber，degreesofanyquality，andcontrariety；noneofwhichareimply’dinthisproposition，Whateverhasabeginninghasalsoacauseofexistence。Thatpropositionthereforeisnotintuitivelycertain。Atleastanyone，whowou’dassertittobeintuitivelycertain，mustdenythesetobetheonlyinfalliblerelations，andmustfindsomeotherrelationofthatkindtobeimply’dinit；whichitwillthenbetimeenoughtoexamine。
　　Buthereisanargument，whichprovesatonce，thattheforegoingpropositionisneitherintuitivelynordemonstrablycertain。Wecanneverdemonstratethenecessityofacausetoeverynewexistence，ornewmodificationofexistence，withoutshewingatthesametimetheimpossibilitythereis，thatanythingcaneverbegintoexistwithoutsomeproductiveprinciple；andwherethelatterpropositioncannotbeprov’d，wemustdespairofeverbeingabletoprovetheformer。Nowthatthelatterpropositionisutterlyincapableofademonstrativeproof，wemaysatisfyourselvesbyconsideringthatasalldistinctideasareseparablefromeachother，andastheideasofcauseandeffectareevidentlydistinct，’twillbeeasyforustoconceiveanyobjecttobenon-existentthismoment，andexistentthenext，withoutconjoiningtoitthedistinctideaofacauseorproductiveprinciple。Theseparation，therefore，oftheideaofacausefromthatofabeginningofexistence，isplainlypossiblefortheimagination；andconsequentlytheactualseparationoftheseobjectsissofarpossible，thatitimpliesnocontradictionnorabsurdity；andisthereforeincapableofbeingrefutedbyanyreasoningfrommereideas；withoutwhich’tisimpossibletodemonstratethenecessityofacause。
　　Accordinglyweshallfinduponexamination，thateverydemonstration，whichhasbeenproduc’dforthenecessityofacause，isfallaciousandsophistical。Allthepointsoftimeandplace，16saysomephilosophers，inwhichwecansupposeanyobjecttobe-intoexist，areinthemselvesequal；andunlesstherebesomecause，whichispeculiartoonetimeandtooneplace，andwhichbythatmeansdeterminesandfixestheexistence，itmustremainineternalsuspence；andtheobjectcanneverbegintobe，forwantofsomethingtofixitsbeginning。ButIask；Isthereanymoredifficultyinsupposingthetimeandplacetobefix’dwithoutacause，thantosupposetheexistencetobedeterminedinthatmanner？Thefirstquestionthatoccursonthissubjectisalways，whethertheobjectshallexistornot:Thenext，whenandwhereitshallbegintoexist。Iftheremovalofacausebeintuitivelyabsurdintheonecase，itmustbesointheother:Andifthatabsurditybenotclearwithoutaproofintheonecase，itwillequallyrequireoneintheother。Theabsurdity，then，oftheonesuppositioncanneverbeaproofofthatoftheother；sincetheyarebothuponthesamefooting，andmuststandorfallbythesamereasoning。
　　Thesecondargument，17whichIfindus’donthishead，laboursunderanequaldifficulty。Everything，’tissaid，musthaveacause；forifanythingwantedacause，itwou’dproduceitself；thatis，existbeforeitexisted；whichisimpossible。Butthisreasoningisplainlyunconclusive；becauseitsupposes，thatinourdenialofacausewestillgrantwhatweexpresslydeny，viz。thattheremustbeacause；whichthereforeistakentobetheobjectitself；andthat，nodoubt，isanevidentcontradiction。Buttosaythatanythingisproduc’d，oftoexpressmyselfmoreproperly，comesintoexistence，withoutacause，isnottoaffirm，that’tisitselfitsowncause；butonthecontraryinexcludingallexternalcauses，excludesafortiorithethingitself，whichiscreated。Anobject，thatexistsabsolutelywithoutanycause，certainlyisnotitsowncause；andwhenyouassert，thattheonefollowsfromtheother，yousupposetheverypointinquestionsandtakeitforgranted，that’tisutterlyimpossibleanythingcaneverbegintoexistwithoutacause，butthat，upontheexclusionofoneproductiveprinciple，wemuststillhaverecoursetoanother。
　　’Tisexactlythesamecasewiththethirdargument，18whichhasbeenemploy’dtodemonstratethenecessityofacause。Whateverisproduc’dwithoutanycause，isproduc’dbynothing；orinotherwords，hasnothingforitscause。Butnothingcanneverbeacause，nomorethanitcanbesomething，orequaltotworightangles。Bythesameintuition，Thatweperceivenothingnottobeequaltotworightangles，ornottobesomething，weperceive，thatitcanneverbeacause；andconsequentlymustperceive，thateveryobjecthasarealcauseofitsexistence。
　　Ibelieveitwillnotbenecessarytoemploymanywordsinshewingtheweaknessofthisargument，afterwhatIhavesaidoftheforegoing。Theyareallofthemfoundedonthesamefallacy，andarederiv’dfromthesameturnofthought。’Tissufficientonlytoobserve，thatwhenweexcludeallcauseswereallydoexcludethem，andneithersupposenothingnortheobjectitselftobethecausesoftheexistence；andconsequentlycandrawnoargumentfromtheabsurdityofthesesuppositionstoprovetheabsurdityofthatexclusion。Ifeverythingmusthaveacause，itfollows，thatupontheexclusionofothercauseswemustacceptoftheobjectitselforofnothingascauses。But’tistheverypointinquestion，whethereverythingmusthaveacauseornot；andtherefore，accordingtoalljustreasoning，itoughtnevertobetakenforgranted。
　　Theyarestillmorefrivolous，whosay，thateveryeffectmusthavea，cause，because’tisimply’dintheveryideaofeffect。Everyeffectnecessarilypre-supposesacause；effectbeingarelativeterm，ofwhichcauseisthecorrelative。Butthisdoesnotprove，thateverybeingmustbeprecededbyacause；nomorethanitfollows，becauseeveryhusbandmusthaveawife，thatthereforeeverymanmustbemarry’d。Thetruestateofthequestionis，whethereveryobject，whichbeginstoexist，mustoweitsexistencetoacause:andthisIassertneithertobeintuitivelynordemonstrativelycertain，andhopetohaveprov’ditsufficientlybytheforegoingarguments。
　　Sinceitisnotfromknowledgeoranyscientificreasoning，thatwederivetheopinionofthenecessityofacausetoeverynewproduction，thatopinionmustnecessarilyarisefromobservationandexperience。Thenextquestion，then，shou’dnaturallybe，howexperiencegivesrisetosuchaprinciple？ButasIfinditwillbemoreconvenienttosinkthisquestioninthefollowing，Whyweconclude，thatsuchparticularcausesmustnecessarilyhavesuchparticularerects，andwhyweformaninferencefromonetoanother？weshallmakethatthesubjectofourfutureenquiry。’Twill，perhaps，befoundintheend，thatthesameanswerwillserveforbothquestions。
　　OftheComponentPartsofourReasoningsConcerningCauseandEffect。
　　Tho’themindinitsreasoningsfromcausesoreffectscarriesitsviewbeyondthoseobjects，whichitseesorremembers，itmustneverlosesightofthementirely，norreasonmerelyuponitsownideas，withoutsomemixtureofimpressions，oratleastofideasofthememory，whichareequivalenttoimpressions。Whenweinfereffectsfromcauses，wemustestablishtheexistenceofthesecauses；whichwehaveonlytwowaysofdoing，eitherbyanimmediateperceptionofourmemoryorsenses，orbyaninferencefromothercauses；whichcausesagainwemustascertaininthesamemanner，eitherbyapresentimpression，orbyaninferencefromtheircauses，andsoon，tillwearriveatsomeobject，whichweseeorremember。’Tisimpossibleforustocarryonourinferencesininfinitum；andtheonlything，thatcanstopthem，isanimpressionofthememoryorsenses，beyondwhichthereisnoroomfordoubtorenquiry。
　　Togiveaninstanceofthis，wemaychuseanypointofhistory，andconsiderforwhatreasonweeitherbelieveorrejectit。ThuswebelievethatCaesarwaskill’dinthesenate-houseontheidesofMarch；andthatbecausethisfactisestablishedontheunanimoustestimonyofhistorians，whoagreetoassignthisprecisetimeandplacetothatevent。Herearecertaincharactersandletterspresenteithertoourmemoryorsenses；whichcharacterswelikewiseremembertohavebeenus’dasthesignsofcertainideas；andtheseideaswereeitherinthemindsofsuchaswereimmediatelypresentatthataction，andreceiv’dtheideasdirectlyfromitsexistence；ortheywerederiv’dfromthetestimonyofothers，andthatagainfromanothertestimony，byavisiblegradation，’tillwearriveatthosewhowereeyewitnessesandspectatorsoftheevent。’Tisobviousallthischainofargumentorconnexionofcausesandeffects，isatfirstfoundedonthosecharactersorletters，whichareseenorremembered，andthatwithouttheauthorityeitherofthememoryorsensesourwholereasoningwou’dbechimericalandwithoutfoundation。Everylinkofthechainwou’dinthatcasehanguponanother；buttherewou’dnotbeanythingfix’dtooneendofit，capableofsustainingthewhole；andconsequentlytherewou’dbenobeliefnorevidence。Andthisactuallyisthecasewithallhypotheticalarguments，orreasoningsuponasupposition；therebeinginthem，neitheranypresentimpression，norbeliefofarealexistence，Ineednotobserve，that’tisnojustobjectiontothepresentdoctrine，thatwecanreasonuponourpastconclusionsorprinciples，withouthavingrecoursetothoseimpressions，fromwhichtheyfirstarose。Forevensupposingtheseimpressionsshou’dbeentirelyeffac’dfromthememory，theconvictiontheyproduc’dmaystillremain；and’tisequallytrue，thatallreasoningsconcerningcausesandeffectsareoriginallyderiv’dfromsomeimpression；inthesamemanner，astheassuranceofademonstrationproceedsalwaysfromacomparisonofideas，tho’itmaycontinueafterthecomparisonisforgot。
　　OftheImpressionsoftheSensesandMemory。
　　Inthiskindofreasoning，then，fromcausation，weemploymaterials，whichareofamix’dandheterogeneousnature，andwhich，howeverconnected，areyetessentiallydifferentfromeachother。Allourargumentsconcerningcausesandeffectsconsistbothofanimpressionofthememoryor，senses，andoftheideaofthatexistence，whichproducestheobjectoftheimpression，orisproduc’dbyit。Herethereforewehavethreethingstoexplain，viz。First，Theoriginalimpression。Secondly，Thetransitiontotheideaoftheconnectedcauseoreffect。Thirdly，Thenatureandqualitiesofthatidea。
　　Astothoseimpressions，whicharisefromthesenses，theirultimatecauseis，inmyopinion，perfectlyinexplicablebyhumanreason，and’twillalwaysbeimpossibletodecidewithcertainty，whethertheyariseimmediatelyfromtheobject，orareproduc’dbythecreativepowerofthemind，orarederiv’dfromtheauthorofourbeing。Norissuchaquestionanywaymaterialtoourpresentpurpose。Wemaydrawinferencesfromthecoherenceofourperceptions，whethertheybetrueorfalse；whethertheyrepresentnaturejustly，orbemereillusionsofthesenses。
　　Whenwesearchforthecharacteristic，whichdistinguishesthememoryfromtheimagination，wemustimmediatelyperceive，thatitcannotlieinthesimpleideasitpresentstous；sinceboththesefacultiesborrowtheirsimpleideasfromtheimpressions，andcannevergobeyondtheseoriginalperceptions。Thesefacultiesareaslittledistinguishedfromeachotherbythearrangementoftheircomplexideas。Fortho’itbeapeculiarpropertyofthememorytopreservetheoriginalorderandpositionofitsideas，whiletheimaginationtransposesandchangesthem，asitpleases；yetthisdifferenceisnotsufficienttodistinguishthemintheiroperation，ormakeusknowtheonefromtheother；itbeingimpossibletorecalthepastimpressions，inordertocomparethemwithourpresentideas，andseewhethertheirarrangementbeexactlysimilar。Sincethereforethememory，isknown，neitherbytheorderofitscomplexideas，northenatureofitssimpleones；itfollows，thatthedifferencebetwixtitandtheimaginationliesinitssuperiorforceandvivacity。Amanmayindulgehisfancyinfeigninganypastsceneofadventures；norwou’dtherebeanypossibilityofdistinguishingthisfromaremembranceofalikekind，werenottheideasoftheimaginationfainterandmoreobscure。
　　[Thefollowingtwoparagraphsareinsertedfromtheappendix。]
　　Itfrequentlyhappens，thatwhentwomenhavebeenengag’dinanysceneofaction，theoneshallrememberitmuchbetterthantheother，andshallhaveallthedifficultyintheworldtomakehiscompanionrecollectit。Herunsoverseveralcircumstancesinvain；mentionsthetime，theplace，thecompany，whatwassaid，whatwasdoneonallsides；tillatlasthehitsonsomeluckycircumstance，thatrevivesthewhole，andgiveshisfriendaperfectmemoryofeverything。Herethepersonthatforgetsreceivesatfirstalltheideasfromthediscourseoftheother，withthesamecircumstancesoftimeandplace；tho’heconsidersthemasmerefictionsoftheimagination。Butassoonasthecircumstanceismention’d，thattouchesthememory，theverysameideasnowappearinanewlight，andhave，inamanner，adifferentfeelingfromwhattheyhadbefore。Withoutanyotheralteration，besidethatofthefeeling，theybecomeimmediatelyideasofthememory，andareassentedto。
　　Since，therefore，theimaginationcanrepresentallthesameobjectsthatthememorycanoffertous，andsincethosefacultiesareonlydistinguishedbythedifferentfeelingoftheideastheypresent，itmaybepropertoconsiderwhatisthenatureofthatfeeling。AndhereIbelieveeveryonewillreadilyagreewithme，thattheideasofthememoryaremorestrongandlivelythanthoseofthefancy。
　　Apainter，whointendedtorepresentapassionoremotionofanykind，wou’dendeavourtogetasightofapersonactuatedbyalikeemotion，inordertoenlivenhisideas，andgivethemaforceandvivacitysuperiortowhatisfoundinthose，whicharemerefictionsoftheimagination。Themorerecentthismemoryis，thecleareristheidea；andwhenafteralongintervalhewou’dreturntothecontemplationofhisobject，healwaysfindsitsideatobemuchdecay’d，ifnotwhollyobliterated。Wearefrequentlyindoubtconcerningtheideasofthememory，astheybecomeveryweakandfeeble；andareatalosstodeterminewhetheranyimageproceedsfromthefancyorthememory，whenitisnotdrawninsuchlivelycoloursasdistinguishthatlatterfaculty。Ithink，Iremembersuchanevent，saysone；butamnotsure。Alongtractoftimehasalmostwornitoutofmymemory，andleavesmeuncertainwhetherornotitbethepureoffspringofmyfancy。
　　Andasanideaofthememory，bylosingitsforceandvivacity，maydegeneratetosuchadegree，astobetakenforanideaoftheimagination；soontheotherhandanideaoftheimaginationmayacquiresuchaforceandvivacity，astopassforanideaofthememory，，andcounterfeititseffectsonthebeliefandjudgment。Thisisnotedinthecaseofliars；whobythefrequentrepetitionoftheirlies，comeatlasttobelieveandrememberthem，asrealities；customandhabithavinginthiscase，asinmanyothers，thesameinfluenceonthemindasnature，andinfixingtheideawithequalforceandvigour。
　　Thusitappears，thatthebelieforassent，whichalwaysattendsthememoryandsenses，isnothingbutthevivacityofthoseperceptionstheypresent；andthatthisalonedistinguishesthemfromtheimagination。Tobelieveisinthiscasetofeelanimmediateimpressionofthesenses，orarepetitionofthatimpressioninthememory。’Tismerelytheforceandlivelinessoftheperception，whichconstitutesthefirstactofthejudgment，andlaysthefoundationofthatreasoning，whichwebuilduponit，whenwetracetherelationofcauseandeffect。
　　OftheInferencefromtheImpressiontotheIdea。
　　’Tiseasytoobserve，thatintracingthisrelation，theinferencewedrawfromcausetoeffect，isnotderiv’dmerelyfromasurveyoftheseparticularobjects，andfromsuchapenetrationintotheiressencesasmaydiscoverthedependanceoftheoneupontheother。Thereisnoobject。，whichimpliestheexistenceofanyotherifweconsidertheseobjectsinthemselves，andneverlookbeyondtheideaswhichweformofthem。Suchaninferencewou’damounttoknowledge，andwou’dimplytheabsolutecontradictionandimpossibilityofconceivinganythingdifferent。Butasalldistinctideasareseparable，’tisevidenttherecanbenoimpossibilityofthatkind。Whenwepassfromapresentimpressiontotheideaofanyobject，wemightpossiblyhaveseparatedtheideafromtheimpression，andhavesubstitutedanyotherideainitsroom。
　　’TisthereforebyEXPERIENCEonly，thatwecaninfertheexistenceofoneobjectfromthatofanother。Thenatureofexperienceisthis。Weremembertohavehadfrequentinstancesoftheexistenceofonespeciesofobjects；andalsoremember，thattheindividualsofanotherspeciesofobjectshavealwaysattendedthem，andhaveexistedinaregularorderofcontiguity-andsuccessionwithregardtothem。Thusweremember，tohaveseenthatspeciesofobjectwecallflame，andtohavefeltthatspeciesofsensationwecallheat。Welikewisecalltomindtheirconstantconjunctioninallpastinstances。Withoutanyfartherceremony，wecalltheonecauseandtheothereffect，andinfertheexistenceoftheonefromthatoftheother。’Inallthoseinstances，fromwhichwelearntheconjunctionofparticularcausesandeffects，boththecausesandeffectshavebeenperceiv’dbythesenses，andarerememberedButinallcases，whereinwereasonconcerningthem，thereisonlyoneperceiv’dorremembered，andtheotherissupply’dinconformitytoourpastexperience。
　　Thusinadvancingwehaveinsensiblydiscoveredanewrelationbetwixtcauseandeffect，whenweleastexpectedit，andwereentirelyemploy’duponanothersubject。ThisrelationistheirCONSTANTCONJUNCTION。Contiguityandsuccessionarenotsufficienttomakeuspronounceanytwoobjectstobecauseandeffect，unlessweperceive，thatthesetworelationsarepreserv’dinseveralinstances。Wemaynowseetheadvantageofquittingthedirectsurveyofthisrelation，inordertodiscoverthenatureofthatnecessaryconnexion，whichmakessoessentialapartofit。Therearehopes，thatbythismeanswemayatlastarriveatourpropos’dend；tho’totellthetruth，thisnew-discover’drelationofaconstantconjunctionseemstoadvanceusbutverylittleinourway。Foritimpliesnomorethanthis，thatlikeobjectshavealwaysbeenplac’dinlikerelationsofcontiguityandsuccession；anditseemsevident，atleastatfirstsight，thatbythismeanswecanneverdiscoveranynewidea，andcanonlymultiply，butnotenlargetheobjectsofourmind。Itmaybethought，thatwhatwelearnnotfromoneobject，wecanneverlearnfromahundred，whichareallofthesamekind，andareperfectlyresemblingineverycircumstance。Asoursensesshewusinoneinstancetwobodies，ormotions，orqualitiesincertainrelationsofsuccess]andcontiguity；soourmemorypresentsusonlywithamultitudeofinstances，whereinwealwaysfindlikebodies，motions，orqualitiesinlikerelations。Fromthemererepetitionofanypastimpression，eventoinfinity，thereneverwillariseanyneworiginalidea，suchasthatofanecessaryconnexion；andthenumberofimpressionshasinthiscasenomoreeffectthanifweconfin’dourselvestooneonly。Buttho’thisreasoningseemsjustandobvious；yetasitwou’dbefollytodespairtoosoon，weshallcontinuethethreadofourdiscourse；andhavingfound，thatafterthediscoveryoftheconstantconjunctionofanyobjects，wealwaysdrawaninferencefromoneobjecttoanother，weshallnowexaminethenatureofthatinference，andofthetransitionfromtheimpressiontotheidea。Perhaps’twillappearintheend，thatthenecessaryconnexiondependsontheinference，insteadoftheinference’sdependingonthenecessaryconnexion。
　　Sinceitappears，thatthetransitionfromanimpressionpresenttothememoryorsensestotheideaofanobject，whichwecallcauseoreffect，isfoundedonpastexperience，andonourremembranceoftheirconstantconjunction，thenextquestionis，Whetherexperienceproducestheideabymeansoftheunderstandingorimagination；whetherwearedetermin’dbyreasontomakethetransition，orbyacertainassociationandrelationofperceptions。Ifreasondeterminedus，itwou’dproceeduponthatprinciple，thatinstances，ofwhichwehavehadnoexperience，mustresemblethose，ofwhichwehavehadexperience，andthatthecourseofnaturecontinuesalwaysuniformlythesame。Inorderthereforetoclearupthismatter，letusconsiderallthearguments，uponwhichsuchapropositionmaybesuppos’dtobefounded；andasthesemustbederiv’deitherfromknowledgeorprobability，letuscastoureveoneachofthesedegreesofevidence，andseewhethertheyaffordanyjustconclusionofthisnature。
　　Ourforegoingmethodofreasoningwilleasilyconvinceus，thattherecanbenodemonstrativeargumentstoprove，thatthoseinstances，ofwhichwehave，hadnoexperience，resemblethose，ofwhichwehavehadexperience。Wecanatleastconceiveachangeinthecourseofnature；whichsufficientlyproves，thatsuchachangeisnotabsolutelyimpossible。Toformaclearideaofanything，isanundeniableargumentforitspossibility，andisalonearefutationofanypretendeddemonstrationagainstit。
　　Probability，asitdiscoversnottherelationsofideas，consideredassuch，butonlythoseofobjects，mustinsomerespectsbefoundedontheimpressionsofourmemoryandsenses，andinsomerespectsonourideas。Weretherenomixtureofanyimpressioninourprobablereasonings，theconclusionwou’dbeentirelychimerical:Andweretherenomixtureofideas，theactionofthemind，inobservingtherelation，wou’d，properlyspeaking，besensation，notreasoning。’Tisthereforenecessary，thatinallprobablereasoningstherebesomethingpresenttothemind，eitherseenorremember’d；andthatfromthisweinfersomethingconnectedwithit，whichisnotseennorremember’d。
　　Theonlyconnexionorrelationofobjects，whichcanleadusbeyondtheimmediateimpressionsofourmemoryandsenses，isthatofcauseandeffect；andthatbecause’tistheonlyone，onwhichwecanfoundajustinferencefromoneobjecttoanother。Theideaofcauseandeffectisderiv’dfromexperience，whichinformsus，thatsuchparticularobjects，inallpastinstances，havebeenconstantlyconjoin’dwitheachother:Andasanobjectsimilartooneoftheseissuppos’dtobeimmediatelypresentinitsimpression，wethencepresumeontheexistenceofonesimilartoitsusualattendant。Accordingtothisaccountofthings，whichis，Ithink，ineverypointunquestionable，probabilityisfoundedonthepresumptionofaresemblancebetwixtthoseobjects，ofwhichwehavehadexperience，andthose，ofwhichwehavehadnone；andtherefore’tisimpossiblethispresumptioncanarisefromprobability。Thesameprinciplecannotbeboththe，causeandeffectofanother；andthisis，perhaps，theonlypropositionconcerningthatrelation，whichiseitherintuitivelyordemonstrativelycertain。
　　Shou’danyonethinktoeludethisargument；andwithoutdeterminingwhetherourreasoningonthissubjectbederiv’dfromdemonstrationorprobability，pretendthatallconclusionsfromcausesandeffectsarebuiltonsolidreasoning:Icanonlydesire，thatthisreasoningmaybeproduc’d，inordertobeexpos’dtoourexamination。Itmay，perhaps，besaid，thatafterexperienceoftheconstantconjunctionofcertainobjects，wereasoninthefollowingmanner。Suchanobjectisalwaysfoundtoproduceanother。’Tisimpossibleitcou’dhavethiseffect，ifitwasnotendow’dwithapowerofproduction。Thepowernecessarilyimpliestheeffect；andthereforethereisajustfoundationfordrawingaconclusionfromtheexistenceofoneobjecttothatofitsusualattendant。Thepastproductionimpliesapower:Thepowerimpliesanewproduction:Andthenewproductioniswhatweinferfromthepowerandthepastproduction。
　　’Twereeasyformetoshewtheweaknessofthisreasoning，wereIwillingtomakeuseofthoseobservations，Ihavealreadymade，thattheideaofproductionisthesamewiththatofcausation，andthatnoexistencecertainlyanddemonstrativelyimpliesapowerinanyotherobject；orwereitpropertoanticipatewhatIshallhaveoccasiontoremarkafterwardsconcerningtheideaweformofpowerandefficacy。Butassuchamethodofproceedingmayseemeithertoweakenmysystem，byrestingonepartofitonanother，ortobreedaconfusioninmyreasoning，Ishallendeavourtomaintainmypresentassertionwithoutanysuchassistance。
　　Itshallthereforebeallow’dforamoment，thattheproductionofoneobjectbyanotherinanyoneinstanceimpliesapower；andthatthispowerisconnectedwithitseffect。Butithavingbeenalreadyprov’d，thatthepowerliesnotinthesensiblequalitiesofthecause；andtherebeingnothingbutthesensiblequalitiespresenttous；Iask，whyinotherinstancesyoupresumethatthesamepowerstillexists，merelyupontheappearanceofthesequalities？Yourappealtopastexperiencedecidesnothinginthepresentcase；andattheutmostcanonlyprove，thatthatveryobject，whichproduc’danyother，wasatthatveryinstantendow’dwithsuchapower；butcanneverprove，thatthesamepowermustcontinueinthesameobjectorcollectionofsensiblequalities；muchless，thatalikepowerisalwaysconjoin’dwithlikesensiblequalities。Shou’ditbesaid，thatwehaveexperience，thatthesamepowercontinuesunitedwiththesameobject，andthatlikeobjectsareendow’dwithlikepowers，Iwou’drenewmyquestion，whyfromthisexperienceweformanyconclusionbeyondthosepastinstances，ofwhichwehavehadexperience。Ifyouanswerthisquestionin，thesamemannerasthepreceding，youranswergivesstilloccasiontoa-newquestionofthesamekind，evenininfinitum；whichclearlyproves，thattheforegoingreasoninghadnojustfoundation。
　　Thusnotonlyourreasonfailsusinthediscoveryoftheultimateconnexionofcausesandeffects，butevenafterexperiencehasinform’dusoftheirconstantconjunction，’tisimpossibleforustosatisfyourselvesbyourreason，whyweshou’dextendthatexperiencebeyondthoseparticularinstances，whichhavefallenunderourobservation。Wesuppose，butareneverabletoprove，thattheremustbearesemblancebetwixtthoseobjects，ofwhichwehavehadexperience，andthosewhichliebeyondthereachofourdiscovery。
　　Wehavealreadytakennoticeofcertainrelations，whichmakeuspassfromoneobjecttoanother，eventho’therebenoreasontodetermineustothattransition；andthiswemayestablishforageneralrule，thatwhereverthemindconstantlyanduniformlymakesatransitionwithoutanyreason，itisinfluenc’dbytheserelations。Nowthisisexactlythepresentcase。Reasoncannevershewustheconnexionofoneobjectwithanother，tho’aidedbyexperience，andtheobservationoftheirconstantconjunctioninallpastinstances。Whenthemind，therefore，passesfromtheideaorimpressionofoneobjecttotheideaorbeliefofanother，itisnotdeterminedbyreason，butbycertainprinciples，whichassociatetogethertheideasoftheseobjects，andunitethemintheimagination。Hadideasnomoreunioninthefancythanobjectsseemtohavetotheunderstanding，wecou’dneverdrawanyinferencefromcausestoeffects，norreposebeliefinanymatteroffact。Theinference，therefore，dependssolelyontheunionofideas。
　　Theprinciplesofunionamongideas，Ihavereduc’dtothreegeneralones，andhaveasserted，thattheideaorimpressionofanyobjectnaturallyintroducestheideaofanyotherobject，thatisresembling，contiguousto，orconnectedwithit。TheseprinciplesIallowtobeneithertheinfalliblenorthesolecausesofanunionamongideas。Theyarenottheinfalliblecauses。ForonemayfixhisattentionduringSometimeonanyoneobjectwithoutlookingfarther。Theyarenotthesolecauses。Forthethoughthasevidentlyaveryirregularmotioninrunningalongitsobjects，andmayleapfromtheheavenstotheearth，fromoneendofthecreationtotheother，withoutanycertainmethodororder。Buttho’Iallowthisweaknessinthesethreerelations，andthisirregularityintheimagination；yetIassertthattheonlygeneralprinciples，whichassociateideas，areresemblance，contiguityandcausation。
　　Thereisindeedaprincipleofunionamongideas，whichatfirstsightmaybeesteem’ddifferentfromanyofthese，butwillbefoundatthebottomtodependonthesameorigin。Whenev’ryindividualofanyspeciesofobjectsisfoundbyexperiencetobeconstantlyunitedwithanindividualofanotherspecies，theappearanceofanynewindividualofeitherspeciesnaturallyconveysthethoughttoitsusualattendant。Thusbecausesuchaparticularideaiscommonlyannex’dtosuchaparticularword，nothingisrequir’dbutthehearingofthatwordtoproducethecorrespondentidea；and’twillscarcebepossibleforthemind，byitsutmostefforts，topreventthattransition。Inthiscaseitisnotabsolutelynecessary，thatuponhearingsuchaparticularsound"weshou’dreflectonanypastexperience，andconsiderwhatideahasbeenusuallyconnectedwiththesound。Theimaginationofitselfsuppliestheplaceofthisreflection，andissoaccustomedtopassfromthewordtotheidea，thatitinterposesnotamoment’sdelaybetwixtthehearingoftheone，andtheconceptionoftheother。
　　Buttho’Iacknowledgethistobeatrueprincipleofassociationamongideas，Iassertittobetheverysamewiththatbetwixttheideasofcauseandeffectsandtobeanessentialpartinallourreasoningsfromthatrelation。Wehavenoothernotionofcauseandeffect，butthatofcertainobjects，whichhavebeenalwaysconjoin’dtogether，andwhichinallpastinstanceshavebeenfoundinseparable。Wecannotpenetrateintothereasonoftheconjunction。Weonlyobservethethingitself，andalwaysfindthatfromtheconstantconjunctiontheobjectsacquireanunionintheimagination。Whentheimpressionofonebecomespresenttous，weimmediatelyformanideaofitsusualattendant；andconsequentlywemayestablishthisasonepartofthedefinitionofanopinionorbelief，that’tisanidearelatedtoorassociatedwithapresentimpression。
　　Thustho’causationbeaphilosophicalrelation，asimplyingcontiguity，succession，andconstantconjunction，yet’tisonlysofarasitisanaturalrelation，andproducesanunionamongourideas，thatweareabletoreasonuponit，ordrawanyinferencefromit。
　　OftheNatureoftheIdeaorBelief。
　　Theideaofanobjectisanessentialpartofthebeliefofit，butnotthewhole。Weconceivemanythings，whichwedonotbelieve。Inorderthentodiscovermorefullythenatureofbelief，orthequalitiesofthoseideasweassentto，letusweighthefollowingconsiderations。
　　’Tisevident，thatallreasoningsfromcausesoreffectsterminateinconclusions，concerningmatteroffact；thatis，concerningtheexistenceofobjectsoroftheirqualities。’Tisalsoevident，thattheidea，ofexistenceisnothingdifferentfromtheideaofanyobject，andthatwhenafterthesimpleconceptionofanythingwewou’dconceiveitasexistent，weinrealitymakenoadditiontooralterationonourfirstidea。Thuswhenweaffirm，thatGodisexistent，wesimplyformtheideaofsuchabeing，asheisrepresentedtous；noristheexistence，whichweattributetohim，conceiv’dbyaparticularidea，whichwejointotheideaofhisotherqualities，andcanagainseparateanddistinguishfromthem。ButIgofarther；andnotcontentwithasserting，thattheconceptionoftheexistenceofanyobjectisnoadditiontothesimpleconceptionofit，Ilikewisemaintain，thatthebeliefoftheexistencejoinsnonewideastothose’whichcomposetheideaoftheobject。WhenIthinkofGod，whenIthinkofhimasexistent，andwhenIbelievehimtobeexistent，myideaofhimneitherencreasesnordiminishes。’Butas’tiscertainthereisagreatdifferencebetwixtthesimpleconceptionoftheexistenceofanobject，andthebeliefofit，andasthisdifferenceliesnotinthepartsorcompositionoftheidea，whichweconceive；itfollows，thatitmustlieinthemanner，inwhichweconceiveit。
　　Supposeapersonpresentwithme，whoadvancespropositions，towhichIdonotassent，thatCaesardy’dinhisbed，thatsilverismorefusible，thanlead，ormercuryheavierthangold；’tisevident，thatnotwithstandingmyincredulity，Iclearlyunderstandhismeaning，andformallthesameideas，whichheforms。Myimaginationisendow’dwiththesamepowersashis；norisitpossibleforhimtoconceiveanyidea，whichIcannotconceive；norconjoinany，whichIcannotconjoin。Ithereforeask，Whereinconsiststhedifferencebetwixtbelievinganddisbelievinganyproposition？Theansweriseasywithregardtopropositions，thatareprov’dbyintuitionordemonstration。Inthatcase，theperson，whoassents，notonlyconceivestheideasaccordingtotheproposition，butisnecessarilydeterminedtoconceivetheminthatparticularmanner，eitherimmediatelyorbytheinterpositionofotherideas。Whateverisabsurdisunintelligible；norisitpossiblefortheimaginationtoconceiveanythingcontrarytoademonstration。Butasinreasoningsfromcausation，andconcerningmattersoffact，thisabsolutenecessitycannottakeplace，andtheimaginationisfreetoconceivebothsidesofthequestion，Istillask，Whereinconsiststhedeferencebetwixtincredulityandbelief？sinceinbothcasestheconceptionoftheideaisequallypossibleandrequisite。
　　’Twillnotbeasatisfactoryanswertosay，thataperson，whodoesnotassenttoapropositionyouadvance；afterhavingconceiv’dtheobjectinthesamemannerwithyou；immediatelyconceivesitinadifferentmanner，andhasdifferentideasofit。Thisanswerisunsatisfactory；notbecauseitcontainsanyfalshood，butbecauseitdiscoversnotallthetruth。’Tiscontest，thatinallcases，whereinwedissentfromanyperson，weconceivebothsidesofthequestion；butaswecanbelieveonlyone，itevidentlyfollows，thatthebeliefmustmakesomedifferencebetwixtthatconceptiontowhichweassent，andthatfromwhichwedissent。Wemaymingle，andunite，andseparate，andconfound，andvaryourideasinahundreddifferentways；but’tillthereappearssomeprinciple，whichfixesoneofthesedifferentsituations，wehaveinrealitynoopinion:Andthisprinciple，asitplainlymakesnoadditiontoourprecedentideas，canonlychangethemannerofourconceivingthem。
　　Alltheperceptionsofthemindareoftwokinds，viz。impressionsandideas，whichdifferfromeachotheronlyintheirdifferentdegreesofforceandvivacity。Ourideasarecopy’dfromourimpressions，andrepresenttheminalltheirparts。Whenyouwou’danywayvarytheideaofaparticularobject，youcanonlyencreaseordiminishitsforceandvivacity。]Ifyoumakeanyotherchangeonit，itrepresentsadifferentobjectorimpression。Thecaseisthesameasincolours。Aparticularshadeofanycolourmayacquireanewdegreeoflivelinessorbrightnesswithoutanyothervariation。Butwhenyouproduceanyothervariation，’tisnolongerthesameshadeorcolour。Sothatasbeliefdoesnothingbutvarythemanner，inwhichweconceiveanyobject，itcanonlybestowonourideasanadditionalforceandvivacity。Anopinion，therefore，orbeliefmaybemostaccuratelydefined，alivelyidearelatedtoorassociatedwithapresentimpression。19
　　Herearetheheadsofthosearguments，whichleadustothisconclusion。Whenweinfertheexistenceofanobjectfromthatofothers，someobjectmustalwaysbepresenteithertothememoryorsenses，inordertobethefoundationofourreasoning；sincethemindcannotrunupwithitsinferencesininfinitum。Reasoncanneversatisfyusthattheexistenceofanyoneobjectdoeseverimplythatofanother；sothatwhenwepassfromtheimpressionofonetotheideaorbeliefofanother，wearenotdetermin’dbyreason，butbycustomoraprincipleofassociation。Butbeliefissomewhatmorethanasimpleidea。’Tisaparticularmannerofforminganidea:Andasthesameideacanonlybevary’dbyavariationofitsdegreesofforceandvivacity；itfollowsuponthewhole，thatbeliefisalivelyideaproduc’dbyarelationtoapresentimpression，accordingtotheforegoingdefinition。
　　[Thisparagraphisinsertedfromtheappendix]
　　Thisoperationofthemind，whichformsthebeliefofanymatteroffact，seemshithertotohavebeenoneofthegreatestmysteriesofphilosophy；tho’noonehassomuchassuspected，thattherewasanydifficultyinexplainingit。FormypartImustown，thatIfindaconsiderabledifficultyinthecase；andthatevenwhenIthinkIunderstandthesubjectperfectly，Iamatalossfortermstoexpressmymeaning。Iconclude，byaninductionwhichseemstomeveryevident，thatanopinionorbeliefisnothingbutanidea，thatisdifferentfromafiction，notinthenature’ortheorderofitsparts，butinthemannerofitsbeingconceiv’d。ButwhenIwou’dexplainthismanner，Iscarcefindanywordthatfullyanswersthecase，butamoblig’dtohaverecoursetoeveryone’sfeeling，inordertogivehimaperfectnotionofthisoperationofthemind。Anideaassentedtofeelsdifferentfromafictitiousidea，thatthefancyalonepresentstous:AndthisdifferentfeelingIendeavourtoexplainbycallingitasuperiorforce，orvivacity，orsolidity，orfirmness，orsteadiness。Thisvarietyofterms，whichmayseemsounphilosophical，isintendedonlytoexpressthatactofthemind，whichrendersrealitiesmorepresenttousthanfictions，causesthemtoweighmoreinthethought，andgivesthemasuperiorinfluenceonthepassionsandimagination。Providedweagreeaboutthething，’tisneedlesstodisputeabouttheterms。Theimaginationhasthecommandoverallitsideas，andcanjoin，andmix，andvarytheminallthewayspossible。Itmayconceiveobjectswithallthecircumstancesofplaceandtime。Itmaysetthem，ina，manner，beforeoureyesintheirtruecolours，justastheymighthaveexisted。Butasitisimpossible，thatthatfacultycanever，ofitself，reachbelief，’tisevident，thatbeliefconsistsnotinthenatureandorderofourideas，butinthemanneroftheirconception，andintheirfeelingtothemind。Tconfess，that’tisimpossibletoexplainperfectlythisfeelingormannerofconception。Wemaymakeuseofwords，thatexpresssomethingnearit。Butitstrueandpropernameisbelief，whichisatermthateveryonesufficientlyunderstandsincommonlife。Andinphilosophywecangonofarther，thanassert，thatitissomethingfeltbythemind，whichdistinguishestheideasofthejudgmentfromthefictionsoftheimagination。Itgivesthemmoreforceandinfluence；makesthemappearofgreaterimportance；infixestheminthemind；andrendersthemthegoverningprinciplesofallouractions。
　　Thisdefinitionwillalsobefoundtobeentirelyconformabletoeveryone’sfeelingandexperience。Nothingismoreevident，thanthatthoseideas，towhichweassent，aremorestrong，firmandvivid，thantheloosereveriesofacastle-builder。Ifonepersonsitsdowntoreadabookasaromance，andanotherasatruehistory，theyplainlyreceivethesameideas，andinthesameorder；nordoestheincredulityoftheone，andthebeliefoftheotherhinderthemfromputtingtheverysamesenseupontheirauthor。Hiswordsproducethesameideasinboth；tho’histestimonyhasnotthesameinfluenceonthem。Thelatterhasamorelivelyconceptionofalltheincidents。Heentersdeeperintotheconcernsofthepersons:representstohimselftheiractions，andcharacters，andfriendships，andenmities:Heevengoessofarastoformanotionoftheirfeatures，andair，andperson。Whiletheformer，whogivesnocredittothetestimonyoftheauthor，hasamorefaintandlanguidconceptionofalltheseparticulars；andexceptonaccountofthestyleandingenuityofthecomposition，canreceivelittleentertainmentfromit。
　　OftheCausesofBelief。
　　Havingthusexplain’dthenatureofbelief，andshewnthatitconsistsinalivelyidearelatedtoapresentimpression；letusnowproceedtoexaminefromwhatprinciplesitisderiv’d，andwhatbestowsthevivacityontheidea。
　　Iwou’dwillinglyestablishitasageneralmaximinthescienceofhumannature，thatwhenanyimpressionbecomespresenttous，itnotonlytransportsthemindtosuchideasasarerelatedtoit，butlikewisecommunicatestothemashareofitsforceandvivacity。Alltheoperationsoftheminddependinagreatmeasureonitsdisposition，whenitperformsthem；andaccordingasthespiritsaremoreorlesselevated，andtheattentionmoreorlessfix’d，theactionwillalwayshavemoreorlessvigourandvivacity。Whenthereforeanyobjectispresented，whichelevatesandenlivensthethought，everyaction，towhichthemindappliesitself，willbemorestrongandvivid，asTongasthatdispositioncontinues，Now’tisevidentthecontinuanceofthedispositiondependsentirelyontheobjects，aboutwhichthemindisemploy’d；andthatanynewobjectnaturallygivesanewdirectiontothespirits，andchangesthedisposition；asonthecontrary，whenthemindfixesconstantlyonthesameobject，orpasseseasilyandinsensiblyalongrelatedobjects，thedispositionhasamuchlongerduration。Henceithappens，thatwhenthemindisonceinliven’dbyapresentimpression，itproceedstoformamorelivelyideaoftherelatedobjects，byanaturaltransitionofthedispositionfromtheonetotheother。Thechangeoftheobjectsissoeasy，thatthemindisscarcesensibleofit，butappliesitselftotheconceptionoftherelatedideawithalltheforceand’vivacityitacquir’dfromthepresentimpression。
　　Ifinconsideringthenatureofrelation，andthatfacilityoftransition，whichisessentialtoit，wecansatisfyourselvesconcerningtherealityofthisphaenomenon，’tiswell:ButImustconfessIplacemychiefconfidenceinexperiencetoprovesomaterialaprinciple。Wemay，therefore，observe，asthefirstexperimenttoourpresentpurpose，thatupontheappearanceofthepictureofanabsentfriend，ourideaofhimisevidentlyinliven’dbytheresemblance，andthateverypassion，whichthatideaoccasions，whetherofjoyorsorrow，acquiresnewforceandvigour。Inproducingthiseffectthereconcurbotharelationandapresentimpression。Wherethepicturebearshimnoresemblance，oratleastwasnotintendedforhim，itneversomuchasconveysourthoughttohim:Andwhereitisabsent，aswellastheperson；tho’themindmaypassfromthethoughtoftheonetothatoftheother；itfeelsitsideatoberatherweekendthaninliven’dbythattransition。Wetakeapleasureinviewingthepictureofafriend，when’tissetbeforeus；butwhen’tisremov’d，ratherchoosetoconsiderhimdirectly，thanbyreflexioninanimage，whichisequallydistinctandobscure。
　　TheceremoniesoftheRomanCatholicreligionmaybeconsider’dasexperimentsofthesamenature。Thedevoteesofthatstrangesuperstitionusuallypleadinexcuseofthemummeries，withwhichtheyareupbraided，thattheyfeelthegoodeffectofthoseexternalmotions，andpostures，andactions，inenliveningtheirdevotion，andquickeningtheirfervour，whichotherwisewou’ddecayaway，ifdirectedentirelytodistantandimmaterialobjects。Weshadowouttheobjectsofourfaith，saythey，insensibletypesandimages，andrenderthemmorepresenttousbytheimmediatepresenceofthesetypes，than’tispossibleforustodo，merelybyanintellectualviewandcontemplation。Sensibleobjectshavealwaysagreaterinfluenceonthefancythananyother；andthisinfluencetheyreadilyconveytothoseideas，towhichtheyarerelated，andwhichtheyResemble。Ishallonlyinferfromthesepractices，andthisreasoning，thattheeffectofresemblanceininliveningtheideaisverycommon；andasineverycasearesemblanceandapresentimpressionmustconcur，weareabundantlysupply’dwithexperimentstoprovetherealityoftheforegoingprinciple。
　　Wemayaddforcetotheseexperimentsbyothersofadifferentkind，inconsideringtheeffectsofcontiguity，aswellasofresemblance。’Tiscertain，thatdistancediminishestheforceofeveryidea，andthatuponourapproachtoanyobject；tho’itdoesnotdiscoveritselftooursenses；itoperatesuponthemindwithaninfluencethatimitatesanimmediateimpression。Thethinkingonanyobjectreadilytransportsthemindtowhatiscontiguous；but’tisonlytheactualpresenceofanobject，thattransportsitwithasuperiorvivacity。WhenIamafewmilesfromhome，whateverrelatestoittouchesmemorenearlythanwhenIamtwohundredleaguesdistant；tho’evenatthatdistancethereflectingonanythingintheneighbourhoodofmyfriendsandfamilynaturallyproducesanideaofthem。Butasinthislattercase，boththeobjectsofthemindareideas；notwithstandingthereisaneasytransitionbetwixtthem；thattransitionaloneisnotabletogiveasuperiorvivacitytoanyoftheideas，forwantofsomeimmediateimpression。20
　　Noonecandoubtbutcausationhasthesameinfluenceastheothertworelations；ofresemblanceandcontiguity。Superstitiouspeoplearefondoftherelicksofsaintsandholymen，forthesamereasonthattheyseekaftertypesandimages，inordertoenliventheirdevotion，andgivethemamoreintimateandstrongconceptionofthoseexemplarylives，whichtheydesiretoimitate。Now’tisevident，oneofthebestrelicksadevoteecou’dprocure，wou’dbethehandyworkofasaint；andifhiscloathsandfurnitureareevertobeconsider’dinthislight，’tisbecausetheywereonceathisdisposal，andweremov’dandaffectedbyhim；inwhichrespecttheyaretobeconsider’dasimperfecteffects，andasconnectedwithhimbyashorterchainofconsequencesthananyofthose，fromwhichwelearntherealityofhisexistence。Thisphaenomenonclearlyproves，thatapresentimpressionwitharelationofcausationmay，inlivenanyidea，andconsequentlyproducebelieforassent，accordingtotheprecedentdefinitionofit。
　　Butwhyneedweseekforotherargumentstoprove，thatapresentimpressionwitharelationortransitionofthefancymayinlivenanyidea，whenthisveryinstanceofourreasoningsfromcauseandeffectwillalonesufficetothatpurpose？’Tiscertainwemusthaveanideaofeverymatteroffact，whichwebelieve。’Tiscertain，thatthisideaarisesonlyfromarelationtoapresentimpression。’Tiscertain，thatthebeliefsuper-addsnothingtotheidea，butonlychangesourmannerofconceivingit，andrendersitmorestrongandlively。Thepresentconclusionconcerningtheinfluenceofrelationistheimmediateconsequenceofallthesesteps；andeverystepappearstomesureendinfallible。Thereentersnothingintothisoperationofthemindbutapresentimpression，alivelyidea，andarelationorassociationinthefancybetwixttheimpressionandidea；sothattherecanbenosuspicionofmistake。
　　Inordertoputthiswholeaffairinafullerlight，letusconsideritasaquestioninnaturalphilosophy，whichwemustdeterminebyexperienceandobservation。Isupposethereisanobjectpresented，fromwhichIdrawacertainconclusion，andformtomyselfideas，whichIamsaidtobelieveorassentto。Here’tisevident，thathoweverthatobject，whichispresenttomysenses，andthatother，whoseexistenceIinferbyreasoning，maybethoughttoinfluenceeachotherbytheirparticularpowersorqualities；yetasthephenomenonofbelief，whichweatpresentexamine，ismerelyinternal，thesepowersandqualities，beingentirelyunknown，canhavenohandinproducingit。’Tisthepresentimpression，whichistobeconsider’dasthetrueandrealcauseoftheidea，andofthebeliefwhichattendsit。Wemustthereforeendeavourtodiscoverbyexperimentstheparticularqualities，bywhich’tisenabledtoproducesoextraordinaryaneffect。
　　FirstthenIobserve，thatthepresentimpressionhasnotthiseffectbyitsownproperpowerandefficacy，andwhenconsideredalone，asasingleperception，limitedtothepresentmoment。Ifind，thatanimpression，fromwhich，onitsfirstappearance，Icandrawnoconclusion，mayafterwardsbecomethefoundationofbelief，whenIhavehadexperienceofitsusualconsequences。Wemustineverycasehaveobserv’dthesameimpressioninpastinstances，andhavefoundittobeconstantlyconjoin’dwithsomeotherimpression。Thisisconfirm’dbysuchamultitudeofexperiments，thatitadmitsnotofthesmallestdoubt。
　　FromasecondobservationIconclude，thatthebelief，whichattendsthepresentimpression，andisproduc’dbyanumberofpastimpressionsandconjunctions；thatthisbelief，Isay，arisesimmediately，withoutanynewoperationofthereasonorimagination。OfthisIcanbecertain，becauseIneveramconsciousofanysuchoperation，andfindnothinginthesubject，onwhichitcanbefounded。NowaswecalleverythingCUSTOM，whichproceedsfromapastrepetition，withoutanynewreasoningorconclusion，we-mayestablishitasacertaintruth，thatallthebelief，whichfollowsuponanypresentimpression，isderiv’dsolelyfromthatorigin。Whenweareaccustomedtoseetwoimpressionsconjoin’dtogether，theappearanceorideaoftheoneimmediatelycarriesustotheideaoftheother。
　　Beingfullysatisfy’donthishead，Imakeathirdsetofexperiments，inordertoknow，whetheranythingberequisite，besidethecustomarytransition，towardstheproductionofthisphaenomenonofbelief。Ithereforechangethefirstimpressionintoanidea；andobserve，thattho’thecustomarytransitiontothecorrelativeideastillremains，yetthereisinrealitynobeliefnorperswasion。Apresentimpression，then，isabsolutelyrequisitetothiswholeoperation；andwhenafterthisIcompareanimpressionwithanidea，andfindthattheironlydifferenceconsistsintheirdifferentdegreesofforceandvivacity，Iconcludeuponthewhole，thatbeliefisamorevividandintenseconceptionofanidea，proceedingfromitsrelationtoapresentimpression。
　　Thusallprobablereasoningisnothingbutaspeciesofsensation。’’Tisnotsolelyinpoetryandmusic，wemustfollowourtasteandsentiment，butlikewiseinphilosophy。WhenIamconvinc’dofanyprinciple，’tisonlyanidea，whichstrikesmorestronglyuponme。WhenIgivethepreferencetoonesetofargumentsaboveanother，Idonothingbutdecidefrommyfeelingconcerningthesuperiorityoftheirinfluence。Objectshavenodiscoverableconnexiontogether；norisitfromanyotherprinciplebutcustomoperatingupontheimagination，thatwecandrawanyinferencefromtheappearanceofonetotheexistenceofanother。
　　’Twillherebeworthourobservation，thatthepastexperience，onwhichallourjudgmentsconcerningcauseandeffectdepend，mayoperateonourmindinsuchaninsensiblemannerasnevertobetakennoticeof，andmayeveninsomemeasurebeunknowntous。Aperson，whostopsshortinhisjourneyuponmeetingariverinhisway，foreseestheconsequencesofhisproceedingforward；andhisknowledgeoftheseconsequencesisconvey’dtohimbypastexperience，whichinformshimofsuchcertainconjunctionsofcausesandeffects。Butcanwethink，thatonthisoccasionhereflectsonanypastexperience，andcallstoremembranceinstances，thathehasseenorheardof，inordertodiscovertheeffectsofwateronanimalbodies？Nosurely；thisisnotthemethod，inwhichheproceedsinhisreasoning。Theideaofsinkingissocloselyconnectedwiththatofwater，andtheideaofsuffocatingwiththatofsinking，thatthemindmakesthetransitionwithouttheassistanceofthememory。Thecustomoperatesbeforewehavetimeforreflection。Theobjectsseemsoinseparable，thatweinterposenotamoment’sdelayinpassingfromtheonetotheother。Butasthistransitionproceedsfromexperience，andnotfromanyprimaryconnexionbetwixttheideas，wemustnecessarilyacknowledge，thatexperiencemayproduceabeliefandajudgmentofcausesandeffectsbyasecretoperation，andwithoutbeingoncethoughtof。Thisremovesallpretext，ifthereyetremainsany，forassertingthatthemindisconvinc’dbyreasoningofthatprinciple，thatinstancesofwhichwehavenoexperience，mustnecessarilyresemblethose，ofwhichwehave。Forweherefind，thattheunderstandingorimaginationcandrawinferencesfrompastexperience，withoutreflectingonit；muchmorewithoutforminganyprincipleconcerningit，orreasoninguponthatprinciple。
　　Ingeneralwemayobserve，thatinallthemostestablishedanduniformconjunctionsofcausesandeffects，suchasthoseofgravity，impulse，solidity，&；c。themindnevercarriesitsviewexpresslytoconsideranypastexperience:Tho’inotherassociationsofobjects，whicharemorerareandunusual，itmayassistthecustomandtransitionofideasbythisreflection。Naywefindinsomecases，thatthereflectionproducesthebeliefwithoutthecustom；ormoreproperlyspeaking，thatthereflectionproducesthecustominanobliqueandartificialmanner。Iexplainmyself。’Tiscertain，thatnotonlyinphilosophy，butevenincommonlife，wemayattaintheknowledgeofaparticularcausemerelybyoneexperiment，provideditbemadewithjudgment，andafteracarefulremovalofallforeignandsuperfluouscircumstances。Nowasafteroneexperimentofthiskind，themind，upontheappearanceeitherofthecauseortheeffect，candrawaninferenceconcerningtheexistenceofitscorrelative；andasahabitcanneverbeacquir’dmerelybyoneinstance；itmaybethought，thatbeliefcannotinthiscasebeesteem’dtheeffectofcustom。Butthisdifficultywillvanish，ifweconsider，thattho’weareheresuppos’dtohavehadonlyoneexperimentofaparticulareffect，yetwehavemanymillionstoconvinceusofthisprinciple；thatlikeobjectsplacedinlikecircumstances，willalwaysproducelikeeffects；andasthisprinciplehasestablisheditselfbyasufficientcustom，itbestowsanevidenceandfirmnessonanyopinion，towhichitcanbeapply’d。Theconnexionoftheideasisnothabitualafteroneexperiment:butthisconnexioniscomprehendedunderanotherprinciple，thatishabitual；whichbringsusbacktoourhypothesis。Inallcaseswetransferourexperiencetoinstances，ofwhichwehavenoexperience，eitherexpresslyortacitly，eitherdirectlyorindirectly。
　　Imustnotconcludethissubjectwithoutobserving，that’tisverydifficulttotalkoftheoperationsofthemindwithperfectproprietyandexactness；becausecommonlanguagehasseldommadeanyverynicedistinctionsamongthem，buthasgenerallycall’dbythesametermallsuchasnearlyresembleeachother。Andasthisisasourcealmostinevitableofobscurityandconfusionintheauthor；soitmayfrequentlygiverisetodoubtsandobjectionsinthereader，whichotherwisehewou’dneverhavedream’dof。Thusmygeneralposition，thatanopinionorbeliefisnothingbutastrongandlivelyideaderiv’dfromapresentimpressionrelatedtoit，maybeliabletothefollowingobjection，byreasonofalittleambiguityinthosewordsstrongandlively。Itmaybesaid，thatnotonlyanimpressionmaygiverisetoreasoning，butthatanideamayalsohavethesameinfluence；especiallyuponmyprinciple，thatallourideasarederiv’dfromcorrespondentimpressions。ForsupposeIformatpresentanidea，ofwhichIhaveforgotthecorrespondentimpression，Iamabletoconcludefromthisidea，thatsuchanimpressiondidonceexist；andasthisconclusionisattendedwithbelief，itmaybeask’d，fromwhencearethequalitiesofforceandvivacityderiv’d，whichconstitutethisbelief？AndtothisIanswerveryreadily，fromthepresentidea。Forasthisideaisnothereconsidered，astherepresentationofanyabsentobject，butasarealperceptioninthemind，ofwhichweareintimatelyconscious，itmustbeabletobestowonwhateverisrelatedtoitthesamequality，callitfirmness，orsolidity，orforce，orvivacity，withwhichthemindreflectsuponit，andisassur’dofitspresentexistence。Theideaheresuppliestheplaceofanimpression，andisentirelythesame，sofarasregardsourpresentpurpose。
　　Uponthesameprinciplesweneednotbesurpriz’dtohearoftheremembranceofanidea:thatis，oftheideaofanidea，andofitsforceandvivacitysuperiortothelooseconceptionsoftheimagination。Inthinkingofourpastthoughtswenotonlydelineateouttheobjects，ofwhichwewerethinking，butalsoconceivetheactionofthemindinthemeditation，thatcertain，ofwhich’tisimpossibletogiveanydefinitionordescription，butwhicheveryonesufficientlyunderstands。Whenthememoryoffersanideaofthis，andrepresentsitaspast，’tiseasilyconceiv’dhowthatideamayhavemorevigourandfirmness，thanwhenwethinkofapastthought，ofwhichwehavenoremembrance。
　　Afterthisanyonewillunderstandhowwemayformtheideaofanimpressionandofanidea，andhowwewaybelievetheexistenceofanimpressionandofanidea。