PARTIII
Andfinally，asitisnotenough，beforecommencingtorebuildthehouseinwhichwelive，thatitbepulleddown，andmaterialsandbuildersprovided，orthatweengageintheworkourselves，accordingtoaplanwhichwehavebeforehandcarefullydrawnout，butasitislikewisenecessarythatwebefurnishedwithsomeotherhouseinwhichwemaylivecommodiouslyduringtheoperations，sothatImightnotremainirresoluteinmyactions，whilemyreasoncompelledmetosuspendmyjudgement，andthatImightnotbepreventedfromlivingthenceforwardinthegreatestpossiblefelicity，Iformedaprovisorycodeofmorals，composedofthreeorfourmaxims，withwhichIamdesiroustomakeyouacquainted。
Thefirstwastoobeythelawsandcustomsofmycountry，adheringfirmlytothefaithinwhich，bythegraceofGod，Ihadbeeneducatedfrommychildhoodandregulatingmyconductineveryothermatteraccordingtothemostmoderateopinions，andthefarthestremovedfromextremes，whichshouldhappentobeadoptedinpracticewithgeneralconsentofthemostjudiciousofthoseamongwhomImightbeliving。ForasIhadfromthattimebeguntoholdmyownopinionsfornoughtbecauseIwishedtosubjectthemalltoexamination，IwasconvincedthatIcouldnotdobetterthanfollowinthemeantimetheopinionsofthemostjudicious；andalthoughtherearesomeperhapsamongthePersiansandChineseasjudiciousasamongourselves，expediencyseemedtodictatethatIshouldregulatemypracticeconformablytotheopinionsofthosewithwhomIshouldhavetolive；anditappearedtomethat，inordertoascertaintherealopinionsofsuch，Ioughtrathertotakecognizanceofwhattheypractisedthanofwhattheysaid，notonlybecause，inthecorruptionofourmanners，therearefewdisposedtospeakexactlyastheybelieve，butalsobecauseverymanyarenotawareofwhatitisthattheyreallybelieve；for，astheactofmindbywhichathingisbelievedisdifferentfromthatbywhichweknowthatwebelieveit，theoneactisoftenfoundwithouttheother。
Also，amidmanyopinionsheldinequalrepute，Ichosealwaysthemostmoderate，asmuchforthereasonthatthesearealwaysthemostconvenientforpractice，andprobablythebest（forallexcessisgenerallyvicious），asthat，intheeventofmyfallingintoerror，Imightbeatlessdistancefromthetruththanif，havingchosenoneoftheextremes，itshouldturnouttobetheotherwhichIoughttohaveadopted。AndI
placedintheclassofextremesespeciallyallpromisesbywhichsomewhatofourfreedomisabridged；notthatIdisapprovedofthelawswhich，toprovideagainsttheinstabilityofmenoffeebleresolution，whenwhatissoughttobeaccomplishedissomegood，permitengagementsbyvowsandcontractsbindingthepartiestopersevereinit，oreven，forthesecurityofcommerce，sanctionsimilarengagementswherethepurposesoughttoberealizedisindifferent：butbecauseIdidnotfindanythingonearthwhichwaswhollysuperiortochange，andbecause，formyselfinparticular，Ihopedgraduallytoperfectmyjudgments，andnottosufferthemtodeteriorate，Iwouldhavedeemeditagravesinagainstgoodsense，if，forthereasonthatIapprovedofsomethingataparticulartime，Ithereforeboundmyselftoholditforgoodatasubsequenttime，whenperhapsithadceasedtobeso，orIhadceasedtoesteemitsuch。
MysecondmaximwastobeasfirmandresoluteinmyactionsasIwasable，andnottoadherelesssteadfastlytothemostdoubtfulopinions，whenonceadopted，thaniftheyhadbeenhighlycertain；imitatinginthistheexampleoftravelerswho，whentheyhavelosttheirwayinaforest，oughtnottowanderfromsidetoside，farlessremaininoneplace，butproceedconstantlytowardsthesamesideinasstraightalineaspossible，withoutchangingtheirdirectionforslightreasons，althoughperhapsitmightbechancealonewhichatfirstdeterminedtheselection；
forinthisway，iftheydonotexactlyreachthepointtheydesire，theywillcomeatleastintheendtosomeplacethatwillprobablybepreferabletothemiddleofaforest。Inthesameway，sinceinactionitfrequentlyhappensthatnodelayispermissible，itisverycertainthat，whenitisnotinourpowertodeterminewhatistrue，weoughttoactaccordingtowhatismostprobable；andevenalthoughweshouldnotremarkagreaterprobabilityinoneopinionthaninanother，weoughtnotwithstandingtochooseoneortheother，andafterwardsconsiderit，insofarasitrelatestopractice，asnolongerdubious，butmanifestlytrueandcertain，sincethereasonbywhichourchoicehasbeendeterminedisitselfpossessedofthesequalities。Thisprinciplewassufficientthenceforwardtoridmeofallthoserepentingsandpangsofremorsethatusuallydisturbtheconsciencesofsuchfeebleanduncertainmindsas，destituteofanyclearanddeterminateprincipleofchoice，allowthemselvesonedaytoadoptacourseofactionasthebest，whichtheyabandonthenext，astheopposite。
Mythirdmaximwastoendeavoralwaystoconquermyselfratherthanfortune，andchangemydesiresratherthantheorderoftheworld，andingeneral，accustommyselftothepersuasionthat，exceptourownthoughts，thereisnothingabsolutelyinourpower；sothatwhenwehavedoneourbestinthingsexternaltous，allwhereinwefailofsuccessistobeheld，asregardsus，absolutelyimpossible：andthissingleprincipleseemedtomesufficienttopreventmefromdesiringforthefutureanythingwhichIcouldnotobtain，andthusrendermecontented；forsinceourwillnaturallyseeksthoseobjectsalonewhichtheunderstandingrepresentsasinsomewaypossibleofattainment，itisplain，thatifweconsiderallexternalgoodsasequallybeyondourpower，weshallnomoreregrettheabsenceofsuchgoodsasseemduetoourbirth，whendeprivedofthemwithoutanyfaultofours，thanournotpossessingthekingdomsofChinaorMexico，andthusmaking，sotospeak，avirtueofnecessity，weshallnomoredesirehealthindisease，orfreedominimprisonment，thanwenowdobodiesincorruptibleasdiamonds，orthewingsofbirdstoflywith。ButIconfessthereisneedofprolongeddisciplineandfrequentlyrepeatedmeditationtoaccustomthemindtoviewallobjectsinthislight；andIbelievethatinthischieflyconsistedthesecretofthepowerofsuchphilosophersasinformertimeswereenabledtorisesuperiortotheinfluenceoffortune，and，amidsufferingandpoverty，enjoyahappinesswhichtheirgodsmighthaveenvied。For，occupiedincessantlywiththeconsiderationofthelimitsprescribedtotheirpowerbynature，theybecamesoentirelyconvincedthatnothingwasattheirdisposalexcepttheirownthoughts，thatthisconvictionwasofitselfsufficienttopreventtheirentertaininganydesireofotherobjects；andovertheirthoughtstheyacquiredaswaysoabsolute，thattheyhadsomegroundonthisaccountforesteemingthemselvesmorerichandmorepowerful，morefreeandmorehappy，thanothermenwho，whateverbethefavorsheapedonthembynatureandfortune，ifdestituteofthisphilosophy，cannevercommandtherealizationofalltheirdesires。
Infine，toconcludethiscodeofmorals，Ithoughtofreviewingthedifferentoccupationsofmeninthislife，withtheviewofmakingchoiceofthebest。And，withoutwishingtoofferanyremarksontheemploymentsofothers，ImaystatethatitwasmyconvictionthatIcouldnotdobetterthancontinueinthatinwhichIwasengaged，viz。，indevotingmywholelifetothecultureofmyreason，andinmakingthegreatestprogressIwasableintheknowledgeoftruth，ontheprinciplesofthemethodwhichIhadprescribedtomyself。Thismethod，fromthetimeIhadbeguntoapplyit，hadbeentomethesourceofsatisfactionsointenseastoleadmeto，believethatmoreperfectormoreinnocentcouldnotbeenjoyedinthislife；andasbyitsmeansIdailydiscoveredtruthsthatappearedtomeofsomeimportance，andofwhichothermenweregenerallyignorant，thegratificationthencearisingsooccupiedmymindthatIwaswhollyindifferenttoeveryotherobject。Besides，thethreeprecedingmaximswerefoundedsinglyonthedesignofcontinuingtheworkofself—
instruction。ForsinceGodhasendowedeachofuswithsomelightofreasonbywhichtodistinguishtruthfromerror，IcouldnothavebelievedthatIoughtforasinglemomenttorestsatisfiedwiththeopinionsofanother，unlessIhadresolvedtoexercisemyownjudgmentinexaminingthesewheneverIshouldbedulyqualifiedforthetask。NorcouldIhaveproceededonsuchopinionswithoutscruple，hadIsupposedthatIshouldtherebyforfeitanyadvantageforattainingstillmoreaccurate，shouldsuchexist。And，infine，Icouldnothaverestrainedmydesires，norremainedsatisfiedhadInotfollowedapathinwhichIthoughtmyselfcertainofattainingalltheknowledgetotheacquisitionofwhichIwascompetent，aswellasthelargestamountofwhatistrulygoodwhichI
couldeverhopetosecureInasmuchasweneitherseeknorshunanyobjectexceptinsofarasourunderstandingrepresentsitasgoodorbad，allthatisnecessarytorightactionisrightjudgment，andtothebestactionthemostcorrectjudgment，thatis，totheacquisitionofallthevirtueswithallelsethatistrulyvaluableandwithinourreach；andtheassuranceofsuchanacquisitioncannotfailtorenderuscontented。
Havingthusprovidedmyselfwiththesemaxims，andhavingplacedtheminreservealongwiththetruthsoffaith，whichhaveeveroccupiedthefirstplaceinmybelief，IcametotheconclusionthatImightwithfreedomsetaboutriddingmyselfofwhatremainedofmyopinions。And，inasmuchasIhopedtobebetterablesuccessfullytoaccomplishthisworkbyholdingintercoursewithmankind，thanbyremaininglongershutupintheretirementwherethesethoughtshadoccurredtome，Ibetookmeagaintotravelingbeforethewinterwaswellended。And，duringtheninesubsequentyears，Ididnothingbutroamfromoneplacetoanother，desirousofbeingaspectatorratherthananactorintheplaysexhibitedonthetheateroftheworld；and，asImadeitmybusinessineachmattertoreflectparticularlyuponwhatmightfairlybedoubtedandproveasourceoferror，Igraduallyrootedoutfrommymindalltheerrorswhichhadhithertocreptintoit。NotthatinthisIimitatedthescepticswhodoubtonlythattheymaydoubt，andseeknothingbeyonduncertaintyitself；for，onthecontrary，mydesignwassinglytofindgroundofassurance，andcastasidethelooseearthandsand，thatImightreachtherockortheclay。Inthis，asappearstome，Iwassuccessfulenough；
for，sinceIendeavoredtodiscoverthefalsehoodorincertitudeofthepropositionsIexamined，notbyfeebleconjectures，butbyclearandcertainreasonings，Imetwithnothingsodoubtfulasnottoyieldsomeconclusionofadequatecertainty，althoughthisweremerelytheinference，thatthematterinquestioncontainednothingcertain。And，justasinpullingdownanoldhouse，weusuallyreservetheruinstocontributetowardstheerection，so，indestroyingsuchofmyopinionsasIjudgedtobeIll—founded，ImadeavarietyofobservationsandacquiredanamountofexperienceofwhichIavailedmyselfintheestablishmentofmorecertain。
Andfurther，IcontinuedtoexercisemyselfinthemethodIhadprescribed；for，besidestakingcareingeneraltoconductallmythoughtsaccordingtoitsrules，IreservedsomehoursfromtimetotimewhichI
expresslydevotedtotheemploymentofthemethodinthesolutionofmathematicaldifficulties，oreveninthesolutionlikewiseofsomequestionsbelongingtoothersciences，butwhich，bymyhavingdetachedthemfromsuchprinciplesofthesesciencesaswereofinadequatecertainty，wererenderedalmostmathematical：thetruthofthiswillbemanifestfromthenumerousexamplescontainedinthisvolume。Andthus，withoutinappearancelivingotherwisethanthosewho，withnootheroccupationthanthatofspendingtheirlivesagreeablyandinnocently，studytoseverpleasurefromvice，andwho，thattheymayenjoytheirleisurewithoutennui，haverecoursetosuchpursuitsasarehonorable，I
wasneverthelessprosecutingmydesign，andmakinggreaterprogressintheknowledgeoftruth，thanImight，perhaps，havemadehadIbeenengagedintheperusalofbooksmerely，orinholdingconversewithmenofletters。
Thesenineyearspassedaway，however，beforeIhadcometoanydeterminatejudgmentrespectingthedifficultieswhichformmatterofdisputeamongthelearned，orhadcommencedtoseektheprinciplesofanyphilosophymorecertainthanthevulgar。Andtheexamplesofmanymenofthehighestgenius，whohad，informertimes，engagedinthisinquiry，but，asappearedtome，withoutsuccess，ledmetoimagineittobeaworkofsomuchdifficulty，thatIwouldnotperhapshaveventuredonitsosoonhadInothearditcurrentlyrumoredthatIhadalreadycompletedtheinquiry。Iknownotwhatwerethegroundsofthisopinion；and，ifmyconversationcontributedinanymeasuretoitsrise，thismusthavehappenedratherfrommyhavingconfessedmyIgnorancewithgreaterfreedomthanthoseareaccustomedtodowhohavestudiedalittle，andexpoundedperhaps，thereasonsthatledmetodoubtofmanyofthosethingsthatbyothersareesteemedcertain，thanfrommyhavingboastedofanysystemofphilosophy。But，asIamofadispositionthatmakesmeunwillingtobeesteemeddifferentfromwhatIreallyam，Ithoughtitnecessarytoendeavorbyallmeanstorendermyselfworthyofthereputationaccordedtome；anditisnowexactlyeightyearssincethisdesireconstrainedmetoremovefromallthoseplaceswhereinterruptionfromanyofmyacquaintanceswaspossible，andbetakemyselftothiscountry，inwhichthelongdurationofthewarhasledtotheestablishmentofsuchdiscipline，thatthearmiesmaintainedseemtobeofuseonlyinenablingtheinhabitantstoenjoymoresecurelytheblessingsofpeaceandwhere，inthemidstofagreatcrowdactivelyengagedinbusiness，andmorecarefuloftheirownaffairsthancuriousaboutthoseofothers，Ihavebeenenabledtolivewithoutbeingdeprivedofanyoftheconveniencestobehadinthemostpopulouscities，andyetassolitaryandasretiredasinthemidstofthemostremotedeserts。
PARTIV
Iamindoubtastotheproprietyofmakingmyfirstmeditationsintheplaceabovementionedmatterofdiscourse；forthesearesometaphysical，andsouncommon，asnot，perhaps，tobeacceptabletoeveryone。Andyet，thatitmaybedeterminedwhetherthefoundationsthatIhavelaidaresufficientlysecure，Ifindmyselfinameasureconstrainedtoadverttothem。Ihadlongbeforeremarkedthat，inrelationtopractice，itissometimesnecessarytoadopt，asifabovedoubt，opinionswhichwediscerntobehighlyuncertain，ashasbeenalreadysaid；butasIthendesiredtogivemyattentionsolelytothesearchaftertruth，Ithoughtthataprocedureexactlytheoppositewascalledfor，andthatIoughttorejectasabsolutelyfalseallopinionsinregardtowhichIcouldsupposetheleastgroundfordoubt，inordertoascertainwhetherafterthatthereremainedaughtinmybeliefthatwaswhollyindubitable。Accordingly，seeingthatoursensessometimesdeceiveus，Iwaswillingtosupposethatthereexistednothingreallysuchastheypresentedtous；andbecausesomemenerrinreasoning，andfallintoparalogisms，evenonthesimplestmattersofgeometry，I，convincedthatIwasasopentoerrorasanyother，rejectedasfalseallthereasoningsIhadhithertotakenfordemonstrations；andfinally，whenIconsideredthattheverysamethoughts（presentations）whichweexperiencewhenawakemayalsobeexperiencedwhenweareasleep，whilethereisatthattimenotoneofthemtrue，I
supposedthatalltheobjects（presentations）thathadeverenteredintomymindwhenawake，hadinthemnomoretruththantheillusionsofmydreams。ButimmediatelyuponthisIobservedthat，whilstIthuswishedtothinkthatallwasfalse，itwasabsolutelynecessarythatI，whothusthought，shouldbesomewhat；andasIobservedthatthistruth，Ithink，thereforeIam（COGITOERGOSUM），wassocertainandofsuchevidencethatnogroundofdoubt，howeverextravagant，couldbeallegedbythescepticscapableofshakingit，IconcludedthatImight，withoutscruple，acceptitasthefirstprincipleofthephilosophyofwhichIwasinsearchInthenextplace，IattentivelyexaminedwhatIwasandasIobservedthatIcouldsupposethatIhadnobody，andthattherewasnoworldnoranyplaceinwhichImightbe；butthatIcouldnotthereforesupposethatIwasnot；andthat，onthecontrary，fromtheverycircumstancethatI
thoughttodoubtofthetruthofotherthings，itmostclearlyandcertainlyfollowedthatIwas；while，ontheotherhand，ifIhadonlyceasedtothink，althoughalltheotherobjectswhichIhadeverimaginedhadbeeninrealityexistent，IwouldhavehadnoreasontobelievethatI
existed；IthenceconcludedthatIwasasubstancewhosewholeessenceornatureconsistsonlyinthinking，andwhich，thatitmayexist，hasneedofnoplace，norisdependentonanymaterialthing；sothat\"I，\"thatistosay，themindbywhichIamwhatIam，iswhollydistinctfromthebody，andisevenmoreeasilyknownthanthelatter，andissuch，thatalthoughthelatterwerenot，itwouldstillcontinuetobeallthatitis。
AfterthisIinquiredingeneralintowhatisessentialItothetruthandcertaintyofaproposition；forsinceIhaddiscoveredonewhichIknewtobetrue，IthoughtthatImustlikewisebeabletodiscoverthegroundofthiscertitude。AndasIobservedthatinthewordsIthink，thereforeI
am，thereisnothingatallwhichgivesmeassuranceoftheirtruthbeyondthis，thatIseeveryclearlythatinordertothinkitisnecessarytoexist，IconcludedthatImighttake，asageneralrule，theprinciple，thatallthethingswhichweveryclearlyanddistinctlyconceivearetrue，onlyobserving，however，thatthereissomedifficultyinrightlydeterminingtheobjectswhichwedistinctlyconceive。
Inthenextplace，fromreflectingonthecircumstancethatIdoubted，andthatconsequentlymybeingwasnotwhollyperfect（forIclearlysawthatitwasagreaterperfectiontoknowthantodoubt），IwasledtoinquirewhenceIhadlearnedtothinkofsomethingmoreperfectthanmyself；andI
clearlyrecognizedthatImustholdthisnotionfromsomenaturewhichinrealitywasmoreperfect。Asforthethoughtsofmanyotherobjectsexternaltome，asofthesky，theearth，light，heat，andathousandmore，Iwaslessatalosstoknowwhencethesecame；forsinceIremarkedinthemnothingwhichseemedtorenderthemsuperiortomyself，Icouldbelievethat，iftheseweretrue，theyweredependenciesonmyownnature，insofarasitpossessedacertainperfection，and，iftheywerefalse，thatIheldthemfromnothing，thatistosay，thattheywereinmebecauseofacertainimperfectionofmynature。Butthiscouldnotbethecasewith—theideaofanaturemoreperfectthanmyself；fortoreceiveitfromnothingwasathingmanifestlyimpossible；and，becauseitisnotlessrepugnantthatthemoreperfectshouldbeaneffectof，anddependenceonthelessperfect，thanthatsomethingshouldproceedfromnothing，itwasequallyimpossiblethatIcouldholditfrommyself：
accordingly，itbutremainedthatithadbeenplacedinmebyanaturewhichwasinrealitymoreperfectthanmine，andwhichevenpossessedwithinitselfalltheperfectionsofwhichIcouldformanyidea；thatistosay，inasingleword，whichwasGod。AndtothisIaddedthat，sinceI
knewsomeperfectionswhichIdidnotpossess，Iwasnottheonlybeinginexistence（Iwillhere，withyourpermission，freelyusethetermsoftheschools）；but，onthecontrary，thattherewasofnecessitysomeothermoreperfectBeinguponwhomIwasdependent，andfromwhomIhadreceivedallthatIpossessed；forifIhadexistedalone，andindependentlyofeveryotherbeing，soastohavehadfrommyselfalltheperfection，howeverlittle，whichIactuallypossessed，Ishouldhavebeenable，forthesamereason，tohavehadfrommyselfthewholeremainderofperfection，ofthewantofwhichIwasconscious，andthuscouldofmyselfhavebecomeinfinite，eternal，immutable，omniscient，all—powerful，and，infine，havepossessedalltheperfectionswhichIcouldrecognizeinGod。ForinordertoknowthenatureofGod（whoseexistencehasbeenestablishedbytheprecedingreasonings），asfarasmyownnaturepermitted，IhadonlytoconsiderinreferencetoallthepropertiesofwhichIfoundinmymindsomeidea，whethertheirpossessionwasamarkofperfection；andIwasassuredthatnoonewhichindicatedanyimperfectionwasinhim，andthatnoneoftherestwasawanting。ThusI
perceivedthatdoubt，inconstancy，sadness，andsuchlike，couldnotbefoundinGod，sinceImyselfwouldhavebeenhappytobefreefromthem。
Besides，Ihadideasofmanysensibleandcorporealthings；foralthoughI
mightsupposethatIwasdreaming，andthatallwhichIsaworimaginedwasfalse，Icouldnot，nevertheless，denythattheideaswereinrealityinmythoughts。But，becauseIhadalreadyveryclearlyrecognizedinmyselfthattheintelligentnatureisdistinctfromthecorporeal，andasIobservedthatallcompositionisanevidenceofdependency，andthatastateofdependencyismanifestlyastateofimperfection，IthereforedeterminedthatitcouldnotbeaperfectioninGodtobecompoundedofthesetwonaturesandthatconsequentlyhewasnotsocompounded；butthatiftherewereanybodiesintheworld，orevenanyintelligences，orothernaturesthatwerenotwhollyperfect，theirexistencedependedonhispowerinsuchawaythattheycouldnotsubsistwithouthimforasinglemoment。
IwasdisposedstraightwaytosearchforothertruthsandwhenIhadrepresentedtomyselftheobjectofthegeometers，whichIconceivedtobeacontinuousbodyoraspaceindefinitelyextendedinlength，breadth，andheightordepth，divisibleintodiverspartswhichadmitofdifferentfiguresandsizes，andofbeingmovedortransposedinallmannerofways（forallthisthegeometerssupposetobeintheobjecttheycontemplate），Iwentoversomeoftheirsimplestdemonstrations。And，inthefirstplace，Iobserved，thatthegreatcertitudewhichbycommonconsentisaccordedtothesedemonstrations，isfoundedsolelyuponthis，thattheyareclearlyconceivedinaccordancewiththerulesIhavealreadylaiddownInthenextplace，Iperceivedthattherewasnothingatallinthesedemonstrationswhichcouldassuremeoftheexistenceoftheirobject：
thus，forexample，supposingatriangletobegiven，Idistinctlyperceivedthatitsthreeangleswerenecessarilyequaltotworightangles，butIdidnotonthataccountperceiveanythingwhichcouldassuremethatanytriangleexisted：while，onthecontrary，recurringtotheexaminationoftheideaofaPerfectBeing，IfoundthattheexistenceoftheBeingwascomprisedintheideainthesamewaythattheequalityofitsthreeanglestotworightanglesiscomprisedintheideaofatriangle，orasintheideaofasphere，theequidistanceofallpointsonitssurfacefromthecenter，orevenstillmoreclearly；andthatconsequentlyitisatleastascertainthatGod，whoisthisPerfectBeing，is，orexists，asanydemonstrationofgeometrycanbe。
Butthereasonwhichleadsmanytopersuadethemselvesthatthereisadifficultyinknowingthistruth，andevenalsoinknowingwhattheirmindreallyis，isthattheyneverraisetheirthoughtsabovesensibleobjects，andaresoaccustomedtoconsidernothingexceptbywayofimagination，whichisamodeofthinkinglimitedtomaterialobjects，thatallthatisnotimaginableseemstothemnotintelligible。Thetruthofthisissufficientlymanifestfromthesinglecircumstance，thatthephilosophersoftheschoolsacceptasamaximthatthereisnothingintheunderstandingwhichwasnotpreviouslyinthesenses，inwhichhoweveritiscertainthattheideasofGodandofthesoulhaveneverbeen；anditappearstomethattheywhomakeuseoftheirimaginationtocomprehendtheseideasdoexactlythesomethingasif，inordertohearsoundsorsmellodors，theystrovetoavailthemselvesoftheireyes；unlessindeedthatthereisthisdifference，thatthesenseofsightdoesnotaffordusaninferiorassurancetothoseofsmellorhearing；inplaceofwhich，neitherourimaginationnoroursensescangiveusassuranceofanythingunlessourunderstandingintervene。
Finally，iftherebestillpersonswhoarenotsufficientlypersuadedoftheexistenceofGodandofthesoul，bythereasonsIhaveadduced，Iamdesirousthattheyshouldknowthatalltheotherpropositions，ofthetruthofwhichtheydeemthemselvesperhapsmoreassured，asthatwehaveabody，andthatthereexiststarsandanearth，andsuchlike，arelesscertain；for，althoughwehaveamoralassuranceofthesethings，whichissostrongthatthereisanappearanceofextravaganceindoubtingoftheirexistence，yetatthesametimenoone，unlesshisintellectisimpaired，candeny，whenthequestionrelatestoametaphysicalcertitude，thatthereissufficientreasontoexcludeentireassurance，intheobservationthatwhenasleepwecaninthesamewayimagineourselvespossessedofanotherbodyandthatweseeotherstarsandanotherearth，whenthereisnothingofthekind。Forhowdoweknowthatthethoughtswhichoccurindreamingarefalseratherthanthoseotherwhichweexperiencewhenawake，sincetheformerareoftennotlessvividanddistinctthanthelatter？
Andthoughmenofthehighestgeniusstudythisquestionaslongastheyplease，Idonotbelievethattheywillbeabletogiveanyreasonwhichcanbesufficienttoremovethisdoubt，unlesstheypresupposetheexistenceofGod。For，inthefirstplaceeventheprinciplewhichIhavealreadytakenasarule，viz。，thatallthethingswhichweclearlyanddistinctlyconceivearetrue，iscertainonlybecauseGodisorexistsandbecauseheisaPerfectBeing，andbecauseallthatwepossessisderivedfromhim：whenceitfollowsthatourideasornotions，whichtotheextentoftheirclearnessanddistinctnessarereal，andproceedfromGod，musttothatextentbetrue。Accordingly，whereaswenotinfrequentlyhaveideasornotionsinwhichsomefalsityiscontained，thiscanonlybethecasewithsuchasaretosomeextentconfusedandobscure，andinthisproceedfromnothing（participateofnegation），thatis，existinusthusconfusedbecausewearenotwhollyperfect。Anditisevidentthatitisnotlessrepugnantthatfalsityorimperfection，insofarasitisimperfection，shouldproceedfromGod，thanthattruthorperfectionshouldproceedfromnothing。ButifwedidnotknowthatallwhichwepossessofrealandtrueproceedsfromaPerfectandInfiniteBeing，howeverclearanddistinctourideasmightbe，weshouldhavenogroundonthataccountfortheassurancethattheypossessedtheperfectionofbeingtrue。
ButaftertheknowledgeofGodandofthesoulhasrendereduscertainofthisrule，wecaneasilyunderstandthatthetruthofthethoughtsweexperiencewhenawake，oughtnotintheslightestdegreetobecalledinquestiononaccountoftheillusionsofourdreams。Forifithappenedthatanindividual，evenwhenasleep，hadsomeverydistinctidea，as，forexample，ifageometershoulddiscoversomenewdemonstration，thecircumstanceofhisbeingasleepwouldnotmilitateagainstitstruth；andasforthemostordinaryerrorofourdreams，whichconsistsintheirrepresentingtousvariousobjectsinthesamewayasourexternalsenses，thisisnotprejudicial，sinceitleadsusveryproperlytosuspectthetruthoftheideasofsense；forwearenotinfrequentlydeceivedinthesamemannerwhenawake；aswhenpersonsinthejaundiceseeallobjectsyellow，orwhenthestarsorbodiesatagreatdistanceappeartousmuchsmallerthantheyare。For，infine，whetherawakeorasleep，weoughtnevertoallowourselvestobepersuadedofthetruthofanythingunlessontheevidenceofourreason。AnditmustbenotedthatIsayofourreason，andnotofourimaginationorofoursenses：thus，forexample，althoughweveryclearlyseethesun，weoughtnotthereforetodeterminethatitisonlyofthesizewhichoursenseofsightpresents；andwemayverydistinctlyimaginetheheadofalionjoinedtothebodyofagoat，withoutbeingthereforeshutuptotheconclusionthatachimaeraexists；
foritisnotadictateofreasonthatwhatwethusseeorimagineisinrealityexistent；butitplainlytellsusthatallourideasornotionscontaininthemsometruth；forotherwiseitcouldnotbethatGod，whoiswhollyperfectandveracious，shouldhaveplacedtheminus。Andbecauseourreasoningsareneversoclearorsocompleteduringsleepaswhenweareawake，althoughsometimestheactsofourimaginationarethenaslivelyanddistinct，ifnotmoresothaninourwakingmoments，reasonfurtherdictatesthat，sinceallourthoughtscannotbetruebecauseofourpartialimperfection，thosepossessingtruthmustinfalliblybefoundintheexperienceofourwakingmomentsratherthaninthatofourdreams。
PARTV
IwouldherewillinglyhaveproceededtoexhibitthewholechainoftruthswhichIdeducedfromtheseprimarybutaswithaviewtothisitwouldhavebeennecessarynowtotreatofmanyquestionsindisputeamongtheearned，withwhomIdonotwishtobeembroiled，Ibelievethatitwillbebetterformetorefrainfromthisexposition，andonlymentioningeneralwhatthesetruthsare，thatthemorejudiciousmaybeabletodeterminewhetheramorespecialaccountofthemwouldconducetothepublicadvantage。IhaveeverremainedfirminmyoriginalresolutiontosupposenootherprinciplethanthatofwhichIhaverecentlyavailedmyselfindemonstratingtheexistenceofGodandofthesoul，andtoacceptastruenothingthatdidnotappeartomemoreclearandcertainthanthedemonstrationsofthegeometershadformerlyappeared；andyetIventuretostatethatnotonlyhaveIfoundmeanstosatisfymyselfinashorttimeonalltheprincipaldifficultieswhichareusuallytreatedofinphilosophy，butIhavealsoobservedcertainlawsestablishedinnaturebyGodinsuchamanner，andofwhichhehasimpressedonourmindssuchnotions，thatafterwehavereflectedsufficientlyuponthese，wecannotdoubtthattheyareaccuratelyobservedinallthatexistsortakesplaceintheworldandfarther，byconsideringtheconcatenationoftheselaws，itappearstomethatIhavediscoveredmanytruthsmoreusefulandmoreimportantthanallIhadbeforelearned，orevenhadexpectedtolearn。
ButbecauseIhaveessayedtoexpoundthechiefofthesediscoveriesinatreatisewhichcertainconsiderationspreventmefrompublishing，Icannotmaketheresultsknownmoreconvenientlythanbyheregivingasummaryofthecontentsofthistreatise。Itwasmydesigntocompriseinitallthat，beforeIsetmyselftowriteit，IthoughtIknewofthenatureofmaterialobjects。Butlikethepainterswho，findingthemselvesunabletorepresentequallywellonaplainsurfaceallthedifferentfacesofasolidbody，selectoneofthechief，onwhichalonetheymakethelightfall，andthrowingtherestintotheshade，allowthemtoappearonlyinsofarastheycanbeseenwhilelookingattheprincipalone；so，fearinglestIshouldnotbeabletocompenseinmydiscourseallthatwasinmymind，Iresolvedtoexpoundsingly，thoughatconsiderablelength，myopinionsregardinglight；thentotaketheopportunityofaddingsomethingonthesunandthefixedstars，sincelightalmostwhollyproceedsfromthem；ontheheavenssincetheytransmitit；ontheplanets，comets，andearth，sincetheyreflectit；andparticularlyonallthebodiesthatareupontheearth，sincetheyareeithercolored，ortransparent，orluminous；andfinallyonman，sinceheisthespectatoroftheseobjects。
Further，toenablemetocastthisvarietyofsubjectssomewhatintotheshade，andtoexpressmyjudgmentregardingthemwithgreaterfreedom，withoutbeingnecessitatedtoadoptorrefutetheopinionsofthelearned，Iresolvedtoleaveallthepeopleheretotheirdisputes，andtospeakonlyofwhatwouldhappeninanewworld，ifGodwerenowtocreatesomewhereintheimaginaryspacesmattersufficienttocomposeone，andweretoagitatevariouslyandconfusedlythedifferentpartsofthismatter，sothatthereresultedachaosasdisorderedasthepoetseverfeigned，andafterthatdidnothingmorethanlendhisordinaryconcurrencetonature，andallowhertoactinaccordancewiththelawswhichhehadestablished。Onthissupposition，I，inthefirstplace，describedthismatter，andessayedtorepresentitinsuchamannerthattomymindtherecanbenothingclearerandmoreintelligible，exceptwhathasbeenrecentlysaidregardingGodandthesoul；forIevenexpresslysupposedthatitpossessednoneofthoseformsorqualitieswhicharesodebatedintheschools，noringeneralanythingtheknowledgeofwhichisnotsonaturaltoourmindsthatnoonecansomuchasimaginehimselfignorantofit。Besides，Ihavepointedoutwhatarethelawsofnature；
and，withnootherprincipleuponwhichtofoundmyreasoningsexcepttheinfiniteperfectionofGod，Iendeavoredtodemonstrateallthoseaboutwhichtherecouldbeanyroomfordoubt，andtoprovethattheyaresuch，thatevenifGodhadcreatedmoreworlds，therecouldhavebeennoneinwhichtheselawswerenotobserved。Thereafter，Ishowedhowthegreatestpartofthematterofthischaosmust，inaccordancewiththeselaws，disposeandarrangeitselfinsuchawayastopresenttheappearanceofheavens；howinthemeantimesomeofitspartsmustcomposeanearthandsomeplanetsandcomets，andothersasunandfixedstars。And，makingadigressionatthisstageonthesubjectoflight，Iexpoundedatconsiderablelengthwhatthenatureofthatlightmustbewhichisfoundinthesunandthestars，andhowthenceinaninstantoftimeittraversestheimmensespacesoftheheavens，andhowfromtheplanetsandcometsitisreflectedtowardstheearth。TothisIlikewiseaddedmuchrespectingthesubstance，thesituation，themotions，andallthedifferentqualitiesoftheseheavensandstars；sothatIthoughtIhadsaidenoughrespectingthemtoshowthatthereisnothingobservableintheheavensorstarsofoursystemthatmustnot，oratleastmaynotappearpreciselyalikeinthoseofthesystemwhichIdescribed。Icamenexttospeakoftheearthinparticular，andtoshowhow，eventhoughI
hadexpresslysupposedthatGodhadgivennoweighttothematterofwhichitiscomposed，thisshouldnotpreventallitspartsfromtendingexactlytoitscenter；howwithwaterandaironitssurface，thedispositionoftheheavensandheavenlybodies，moreespeciallyofthemoon，mustcauseaflowandebb，likeinallitscircumstancestothatobservedinourseas，asalsoacertaincurrentbothofwaterandairfromeasttowest，suchasislikewiseobservedbetweenthetropics；howthemountains，seas，fountains，andriversmightnaturallybeformedinit，andthemetalsproducedinthemines，andtheplantsgrowinthefieldsandingeneral，howallthebodieswhicharecommonlydenominatedmixedorcompositemightbegeneratedand，amongotherthingsinthediscoveriesalludedtoinasmuchasbesidesthestars，Iknewnothingexceptfirewhichproduceslight，Isparednopainstosetforthallthatpertainstoitsnature，——
themannerofitsproductionandsupport，andtoexplainhowheatissometimesfoundwithoutlight，andlightwithoutheat；toshowhowitcaninducevariouscolorsupondifferentbodiesandotherdiversequalities；
howitreducessometoaliquidstateandhardensothers；howitcanconsumealmostallbodies，orconvertthemintoashesandsmoke；andfinally，howfromtheseashes，bythemereintensityofitsaction，itformsglass：forasthistransmutationofashesintoglassappearedtomeaswonderfulasanyotherinnature，Itookaspecialpleasureindescribingit。Iwasnot，however，disposed，fromthesecircumstances，toconcludethatthisworldhadbeencreatedinthemannerIdescribed；foritismuchmorelikelythatGodmadeitatthefirstsuchasitwastobe。
Butthisiscertain，andanopinioncommonlyreceivedamongtheologians，thattheactionbywhichhenowsustainsitisthesamewiththatbywhichheoriginallycreatedit；sothatevenalthoughhehadfromthebeginninggivenitnootherformthanthatofchaos，providedonlyhehadestablishedcertainlawsofnature，andhadlentithisconcurrencetoenableittoactasitiswonttodo，itmaybebelieved，withoutdiscredittothemiracleofcreation，that，inthiswayalone，thingspurelymaterialmight，incourseoftime，havebecomesuchasweobservethematpresent；andtheirnatureismuchmoreeasilyconceivedwhentheyarebeheldcominginthismannergraduallyintoexistence，thanwhentheyareonlyconsideredasproducedatonceinafinishedandperfectstate。
Fromthedescriptionofinanimatebodiesandplants，Ipassedtoanimals，andparticularlytoman。ButsinceIhadnotasyetsufficientknowledgetoenablemetotreatoftheseinthesamemannerasoftherest，thatistosay，bydeducingeffectsfromtheircauses，andbyshowingfromwhatelementsandinwhatmannernaturemustproducethem，IremainedsatisfiedwiththesuppositionthatGodformedthebodyofmanwhollyliketooneofours，aswellintheexternalshapeofthemembersasintheinternalconformationoftheorgans，ofthesamematterwiththatIhaddescribed，andatfirstplacedinitnorationalsoul，noranyotherprinciple，inroomofthevegetativeorsensitivesoul，beyondkindlingintheheartoneofthosefireswithoutlight，suchasIhadalreadydescribed，andwhichI
thoughtwasnotdifferentfromtheheatinhaythathasbeenheapedtogetherbeforeitisdry，orthatwhichcausesfermentationinnewwinesbeforetheyarerunclearofthefruit。For，whenIexaminedthekindoffunctionswhichmight，asconsequencesofthissupposition，existinthisbody，Ifoundpreciselyallthosewhichmayexistinusindependentlyofallpowerofthinking，andconsequentlywithoutbeinginanymeasureowingtothesoul；inotherwords，tothatpartofuswhichisdistinctfromthebody，andofwhichithasbeensaidabovethatthenaturedistinctivelyconsistsinthinking，functionsinwhichtheanimalsvoidofreasonmaybesaidwhollytoresembleus；butamongwhichIcouldnotdiscoveranyofthosethat，asdependentonthoughtalone，belongtousasmen，while，ontheotherhand，IdidafterwardsdiscovertheseassoonasIsupposedGodtohavecreatedarationalsoul，andtohaveannexedittothisbodyinaparticularmannerwhichIdescribed。
But，inordertoshowhowItherehandledthismatter，Imeanheretogivetheexplicationofthemotionoftheheartandarteries，which，asthefirstandmostgeneralmotionobservedinanimals，willaffordthemeansofreadilydeterminingwhatshouldbethoughtofalltherest。AndthattheremaybelessdifficultyinunderstandingwhatIamabouttosayonthissubject，Iadvisethosewhoarenotversedinanatomy，beforetheycommencetheperusaloftheseobservations，totakethetroubleofgettingdissectedintheirpresencetheheartofsomelargeanimalpossessedoflungs（forthisisthroughoutsufficientlylikethehuman），andtohaveshowntothemitstwoventriclesorcavities：inthefirstplace，thatintherightside，withwhichcorrespondtwoveryampletubes，viz。，thehollowvein（venacava），whichistheprincipalreceptacleoftheblood，andthetrunkofthetree，asitwere，ofwhichalltheotherveinsinthebodyarebranches；andthearterialvein（venaarteriosa），inappropriatelysodenominated，sinceitisintruthonlyanartery，which，takingitsriseintheheart，isdivided，afterpassingoutfromit，intomanybrancheswhichpresentlydispersethemselvesalloverthelungs；inthesecondplace，thecavityintheleftside，withwhichcorrespondinthesamemannertwocanalsinsizeequaltoorlargerthanthepreceding，viz。，thevenousartery（arteriavenosa），likewiseinappropriatelythusdesignated，becauseitissimplyaveinwhichcomesfromthelungs，whereitisdividedintomanybranches，interlacedwiththoseofthearterialvein，andthoseofthetubecalledthewindpipe，throughwhichtheairwebreatheenters；andthegreatarterywhich，issuingfromtheheart，sendsitsbranchesalloverthebody。Ishouldwishalsothatsuchpersonswerecarefullyshowntheelevenpellicleswhich，likesomanysmallvalves，openandshutthefourorificesthatareinthesetwocavities，viz。，threeattheentranceofthehollowveinswheretheyaredisposedinsuchamannerasbynomeanstopreventthebloodwhichitcontainsfromflowingintotherightventricleoftheheart，andyetexactlytopreventitsflowingout；threeattheentrancetothearterialvein，which，arrangedinamannerexactlytheoppositeoftheformer，readilypermitthebloodcontainedinthiscavitytopassintothelungs，buthinderthatcontainedinthelungsfromreturningtothiscavity；and，inlikemanner，twoothersatthemouthofthevenousartery，whichallowthebloodfromthelungstoflowintotheleftcavityoftheheart，butprecludeitsreturn；andthreeatthemouthofthegreatartery，whichsufferthebloodtoflowfromtheheart，butpreventitsreflux。Nordoweneedtoseekanyotherreasonforthenumberofthesepelliclesbeyondthisthattheorificeofthevenousarterybeingofanovalshapefromthenatureofitssituation，canbeadequatelyclosedwithtwo，whereastheothersbeingroundaremoreconvenientlyclosedwiththree。Besides，Iwishsuchpersonstoobservethatthegrandarteryandthearterialveinareofmuchharderandfirmertexturethanthevenousarteryandthehollowvein；andthatthetwolastexpandbeforeenteringtheheart，andthereform，asitwere，twopouchesdenominatedtheauriclesoftheheart，whicharecomposedofasubstancesimilartothatoftheheartitself；andthatthereisalwaysmorewarmthintheheartthaninanyotherpartofthebody—andfinally，thatthisheatiscapableofcausinganydropofbloodthatpassesintothecavitiesrapidlytoexpandanddilate，justasallliquorsdowhenallowedtofalldropbydropintoahighlyheatedvessel。
For，afterthesethings，itisnotnecessaryformetosayanythingmorewithaviewtoexplainthemotionoftheheart，exceptthatwhenitscavitiesarenotfullofblood，intothesethebloodofnecessityflows，—
—fromthehollowveinintotheright，andfromthevenousarteryintotheleft；becausethesetwovesselsarealwaysfullofblood，andtheirorifices，whichareturnedtowardstheheart，cannotthenbeclosed。Butassoonastwodropsofbloodhavethuspassed，oneintoeachofthecavities，thesedropswhichcannotbutbeverylarge，becausetheorificesthroughwhichtheypassarewide，andthevesselsfromwhichtheycomefullofblood，areimmediatelyrarefied，anddilatedbytheheattheymeetwith。Inthiswaytheycausethewholehearttoexpand，andatthesametimepresshomeandshutthefivesmallvalvesthatareattheentrancesofthetwovesselsfromwhichtheyflow，andthuspreventanymorebloodfromcomingdownintotheheart，andbecomingmoreandmorerarefied，theypushopenthesixsmallvalvesthatareintheorificesoftheothertwovessels，throughwhichtheypassout，causinginthiswayallthebranchesofthearterialveinandofthegrandarterytoexpandalmostsimultaneouslywiththeheartwhichimmediatelythereafterbeginstocontract，asdoalsothearteries，becausethebloodthathasenteredthemhascooled，andthesixsmallvalvesclose，andthefiveofthehollowveinandofthevenousarteryopenanewandallowapassagetoothertwodropsofblood，whichcausetheheartandthearteriesagaintoexpandasbefore。And，becausethebloodwhichthusentersintotheheartpassesthroughthesetwopouchescalledauricles，itthencehappensthattheirmotionisthecontraryofthatoftheheart，andthatwhenitexpandstheycontract。Butlestthosewhoareignorantoftheforceofmathematicaldemonstrationsandwhoarenotaccustomedtodistinguishtruereasonsfrommereverisimilitudes，shouldventure。withoutexamination，todenywhathasbeensaid，IwishittobeconsideredthatthemotionwhichIhavenowexplainedfollowsasnecessarilyfromtheveryarrangementoftheparts，whichmaybeobservedintheheartbytheeyealone，andfromtheheatwhichmaybefeltwiththefingers，andfromthenatureofthebloodaslearnedfromexperience，asdoesthemotionofaclockfromthepower，thesituation，andshapeofitscounterweightsandwheels。
Butifitbeaskedhowithappensthatthebloodintheveins，flowinginthiswaycontinuallyintotheheart，isnotexhausted，andwhythearteriesdonotbecometoofull，sinceallthebloodwhichpassesthroughtheheartflowsintothem，Ineedonlymentioninreplywhathasbeenwrittenbyaphysician1ofEngland，whohasthehonorofhavingbrokentheiceonthissubject，andofhavingbeenthefirsttoteachthattherearemanysmallpassagesattheextremitiesofthearteries，throughwhichthebloodreceivedbythemfromtheheartpassesintothesmallbranchesoftheveins，whenceitagainreturnstotheheart；sothatitscourseamountspreciselytoaperpetualcirculation。Ofthiswehaveabundantproofintheordinaryexperienceofsurgeons，who，bybindingthearmwithatieofmoderatestraitnessabovethepartwheretheyopenthevein，causethebloodtoflowmorecopiouslythanitwouldhavedonewithoutanyligature；whereasquitethecontrarywouldhappenweretheytobinditbelow；thatis，betweenthehandandtheopening，orweretomaketheligatureabovetheopeningverytight。Foritismanifestthatthetie，moderatelystraightened，whileadequatetohinderthebloodalreadyinthearmfromreturningtowardstheheartbytheveins，cannotonthataccountpreventnewbloodfromcomingforwardthroughthearteries，becausethesearesituatedbelowtheveins，andtheircoverings，fromtheirgreaterconsistency，aremoredifficulttocompress；andalsothatthebloodwhichcomesfromthehearttendstopassthroughthemtothehandwithgreaterforcethanitdoestoreturnfromthehandtotheheartthroughtheveins。
Andsincethelattercurrentescapesfromthearmbytheopeningmadeinoneoftheveins，theremustofnecessitybecertainpassagesbelowtheligature，thatis，towardstheextremitiesofthearmthroughwhichitcancomethitherfromthearteries。Thisphysicianlikewiseabundantlyestablisheswhathehasadvancedrespectingthemotionoftheblood，fromtheexistenceofcertainpellicles，sodisposedinvariousplacesalongthecourseoftheveins，inthemannerofsmallvalves，asnottopermitthebloodtopassfromthemiddleofthebodytowardstheextremities，butonlytoreturnfromtheextremitiestotheheart；andfarther，fromexperiencewhichshowsthatallthebloodwhichisinthebodymayflowoutofitinaveryshorttimethroughasinglearterythathasbeencut，evenalthoughthishadbeencloselytiedintheimmediateneighborhoodoftheheartandcutbetweentheheartandtheligature，soastopreventthesuppositionthatthebloodflowingoutofitcouldcomefromanyotherquarterthantheheart。