Thechapteruponcausation59*isavigorousassertionofMill’sposition。Heacceptsthetraditionalviewofhisschool，thatcausemeansinvariablesequence；buthemakestwoveryimportantamendmentstothepreviousstatements。Asimplesequenceoftwoeventsisnotasufficientindication，howeveroftenrepeated，thattheyarecauseandeffect。Wespeak，hesays，ofaparticulardish’causing’death；buttobeaccuratewemustalsoinclude，aspartofthecause，alltheotherphenomenapresent，themanaswellasthefood，theman’sstateofhealthatthetime，andpossiblyeventhestateoftheatmosphereortheplanet。Therealcausemustincludealltherelevantphenomena。
Thecause，therefore，is，’philosophicallyspeaking，’the’sumtotaloftheconditions，’positiveandnegative，’takentogether，thewholeofthecontingenciesofeverydescription，which，beingrealised，theconsequentinvariablyfollows。’60*Mill’ssecondamendmentismadebysayingthatthecausedoesnotsignifysimply’invariableantecedence，’butalso’unconditional’
sequence。Theremaybe’invariable’sequences，suchasdayandnight——acaseoftenallegedbyReidandothers，whicharenot’unconditional。’Thesun，foranythingwecansay，mightnotrise，andthendaywouldnotfollownight。Therealcondition，therefore，isthepresenceofaluminousbodywithouttheinterpositionofanopaquescreen。61*Theseareundoubtedlymaterialimprovementsuponpreviousstatements；andthisviewbeingadmitted，itfollows，asMillsays，thatthestateofthewholeuniverseistheconsequenceofitsstateatthepreviousinstant。Knowingallthefactsandallthelawsatanytimewecouldpredictallthefuturehistoryoftheuniverse。62*Somecuriousconfusions，itmustbenoticed，resultapparentlyfromMill’suseofpopularlanguage。Themostsingularisimpliedinhisdiscussionofthequestionwhethercauseandeffectcaneverbesimultaneous。Some’causes，’hesays，leavepermanenteffects；
aswordrunsamanthrough，butitneednotremaininhisbodyinorderthathemay’continuedead。’63*The’cause’hereistakentomeanthe’thing’whichwasonceapartofasetofthings，andhasclearlyceasedtomeanthesumofalltheconditions。’Mostthings，’hecontinues，onceproduced，remainastheyaretillsomethingchangesthem。Otherthingsrequirethecontinualpresenceoftheagencieswhichproducedthem。Butsinceallchange，accordingtohim，supposesacause，itisclearthatnotonly’mostthings’butallthingsmustremainastheyaretillsomethingchangesthem。Persistenceisimpliedincausationasmuchaschange，foritismerelytheothersideofthesameprinciple。Inertiaisasmuchassumedinmechanicsasmobility；
foritisthesamethingtosaythatabodyremainsinoneplacewhenthereisnomovingforce，astosaythatwheneveritceasestoremainthereisamovingforce。ThedifferencewhichMillmeanstopointoutisthatsomechangesalterpermanentconditionsofotherchanges，aswhenamancutshisthroatandallvitalprocessescease；whilesometimesthechangeleavespermanentconditionsunaffected，aswhenamanshaveshimself，andhisvitalprocessescontinue。Butinnocaseistheeffectproduced，ashesays，afterthecausehasceased；itisalwaysproducedthroughtheactuallypresentconditions，whichmayhavecomeintotheirpresentstatethroughachangeatsomemoreorlessremoteperiod。Eachlinkinachain，accordingtothecommonmetaphor，dependsuponallthepreviouslinksandmaybesaidtohangfromthem；butthedistantlinkcanonlyactthroughtheintermediatelinks。
Theseslipsimplyavaguenesswhichleadstomoreseriousresults。Mill’saimistoconstructakindoflogicalmachinery——asieve，ifImaysayso，throughwhichwepassallthephenomenaloftheuniverseinordertofindoutwhicharereallylooseandwhichareconnectedbythetiesofcausation。Weareunweavingthecomplexwebofnaturebydiscoveringwhatisthehiddensystemofconnectionsinvirtueofwhichoneeventorthingissomehowfastenedtoanother。Everything，wemaysay，whichappearsiscalledupbysomethingelse——thethunderbythelightning，thedeathbythepoison，andsoforth。Ineverycasewecanreduceastatementofcausationtotheformofanassertionofsequenceorcoexistence。Here，asheobserves，wemeetonedifficulty。Everythingisconnectedwithsomeotherthing。Butthenitmayormustbealsoconnectedwithathird。
Thetwoconnectionsmayinterfere，andwehavetoconsiderhowtheycanbedisentangled。Thisleadstoadistinctiontowhichheattaches，veryrightly，Ithink，thehighestimportance。Insomecases，thecorrectversionofthefactscanbeobtainedbysimplysuperposingthelawsofsimplercases。Abodymovestothenorthundercertainconditions；butotherconditionsforceittomovealsoeastorsouth。Wethenhaveonlytocombinethetwo’laws，’
andtosaythatitismovingbothnorthandeast，thatis，north-east，orperhapstointerpretrestasanequalmovementtobothnorthandsouth。This，asheremarks，representsthegeneralcaseinregardtomechanicalphenomena。Wehavesimplytocombinetworulestogetwhatiscalledindynamics’thecompositionofforces’；and，inaccordancewiththisphase，heusesthegeneralphrase，’thecompositionofcauses。’64*But，asheobserves，thisprincipleisinmanycasesnotapplicable。Inchemicalcombinations，inparticular，wecannotinferthepropertiesofthecompoundfromthepropertiesofthecomponents。Thelawsofsimplesubstanceswillnotgiveusthelawsoftheproduct，andwecanonlylearnthesederivativelawsbyexperiment。Thisholds，stillmoreconspicuously，oforganisedbodies。Fromconsideringthepropertiesofitschemicalconstituentsseparatelyyoucannotdeducethepropertiesofthehumanbody。Wethuscometoakindofknotintheweb；weareatadeadlock，becausethelawsfromwhichwestartaresupersededbyanentirelydifferentsetoflaws。Millmarksthisbyspeakingof’heteropathiclaws。’65*Suchlawsarenotanalysableintosimplelaws。Hethinks，indeed，that’heteropathiclaws’are——
atleast’insomecasesmaybederivedfromtheseparatelaws，accordingtoafixedprinciple。’Thefacttowhichhecallsattentionisundeniable。Wediscovercountlesslawsastothepropertiesofbodieswhichitisimpossibleatpresenteithertoresolveintosimplerlaws，ortodeducefromthelawsoftheconstituentelements。Suchlawsareproperly’empirical。’Theobservationofthefactsassertedisthesoleguaranteeforourbeliefintheirtruth；andtheycanhereducedundernomoregeneralformula。Isthis，however，simplyachallengetothemanofsciencetoinquirefurther，ordoesitopposeaninsuperableobstacletofurtherscientificresearches？Millavowedlylimitshimselfto’ourpresentstateofknowledge。’HerecognisedthatGrove，inhisCorrelationofForces，66*madeoutastrong，thoughstillonlyaprobable，caseforbelievingthata’heteropathiclaw’mayrepresentacompletetransformationofonesetofforcesintoanother。Heat，light，andmagnetismmaybealldifferentmanifestationsofasingleforce——notsomuchcausesofoneanotheras’convertibleintooneanother。’67*Grove，asMilladds，isnot，asmightbesupposed，deviatingintoontology，butgivingastrictlyphilosophicalstatement。Millisherespeakingofagreatprinciple，imperfectlyknownatthetime，whichhasbeenacceptedbymodernscience，andheisquitereadytowelcomeit。Itis，however，noticeablethathestillguardshimselfagainstadmittinganyintrusionof’necessity。’Hewillnotallowthatthedependenceofthepropertiesofcompoundsupontheseelementsmustresultinallcases’accordingtoafixedprinciple。’Themeaningofthismayappearfromhislaterassaultuponthedoctrinethat’likeproduceslike。’Thishereckonsamongthefallacieswhichhediscoversinallmannerofpestilentaprioriphilosophising。Descartes，Spinoza，Leibniz，andColeridgehaveallbeenguiltyofitinvariousforms。68*Wearethereforeundernoobligationtogofurtherwhenwecometototallydisparatephenomenainourseries。Wehaveunravelledourwebsufficientlywhenwefindlawsdisappearingandbeingsupersededbyatotallydifferentsetoflaws，notdescribableeveninthesamelanguage。Thatwemaybeforcedtobecontentwithsucharesultisundeniable。Butitisequallytruethatonemainendofscientifictheoristsistogetroundthisdifficulty。
Withoutinquiringinwhatsensetheaxiomthat’likeproduceslike’maybefallacious，wemustatleastadmitthattogiveascientificlaw——thatis，arulebywhichonesetofeventsisdeduciblefromanother——wemustbeabletoexpressitintermsofsomesinglemeasure。TilIwecangetsuchastatement，wehavenotthecompleteformula。Thereisabreachofcontinuityinourtheories，whichwetrytoremovebyreducingalltheforcestomeasuresassignableintermsofspaceandnumber。Thehypothesisofanetherandvibratingatomsenablesustoregardphenomenaascorrespondinginsomewaytothelawswhich，asMillsays，canbecompoundedbysimplesuperposition，withoutintroducingheterogeneousterms。Thoughhedoesnotcondemnthishypothesis，Millregardsitwithacertainsuspicionasanattempttowanderintoontology，andthesearchforwhatisinitsnatureinaccessible。69*Atanyrate，itdoesnotappeartohimthatfurtherinquiryisnecessarywhenwecometoanirreduciblebreachofcontinuity。toacaseinwhichonesetofphenomenaissimplysupersededbyanother，insteadofbeingtransformableintoit。Ifacompoundismadeofcertainelementsexclusively，aphysicistwouldclearlyinferthatitspropertiesmustbearesultofthepropertiesoftheelementsaccordingto’somefixedprinciple。’Millisonlypreparedtoadmitthatthismaybethecase。Thephysicist，again，seeksforamodeofstatingtheprincipleintheoremscapableofbeingcombinedandsuperposed，whereasMillholdsthatourknowledgemayhavecometoanultimateinsuperableend。
V。PLURALITYOFCAUSES
Itisintheapplicationsofthisviewthatwecometowhatmustberegardedasdownrightfallacies。If，asMillholds，aneffectmaybesomethingabsolutelydisparatefromthecause——anewthingwhichstartsintoexistencewhenitsantecedentoccurs——weareledtoanotherresult。Thereis，then，noapparentreasonwhythesamethingshouldnotspringupinanswertodifferentsummonses。Notonlyisthispossible，but，asMillthinks，itconstantlyoccurs。Thisishisdoctrineofthe’PluralityofCauses。’Agivencause，heholds，canonlyproduceoneeffect。Butagiveneffectmayfollowvariouscauses。Solongastherelationismerelyoneofarbitrarysuccession，notofcontinuity，thisisobviouslypossible。Thefullyscientificview，Itakeit，wouldbethatwhenwespeakof’causeandeffect’wearereallythinkingofasingleprocessregardedindifferentways。Wemayanalysetheprocessdifferentlyfordifferentpurposes，andinferthepastfromthefutureorthefuturefromthepast；butweassumethat，ifwecouldperfectlyunderstandthewholeprocess，therewouldbethoroughcontinuity，andnoabruptsupersessionofonethingoronesetof’laws’byanother。ThiscontinuityispreciselywhatMillsystematicallydenies。Acause，heholds，meansanabsolutebeginningofaneweffect。70*Theprocessbecomesaseriesofdistinctterms——asetof’links’inachain，notaflowofastream。Oneremarkablecaseisenoughtoillustratethepoint。WhenBacon’sclaimstohavefoundedatrulyscientifictheoryareconsidered，itisgenerallysaidthathisguessastothenatureofheatisapointinhisfavour。71*Mill，however，takesthisparticularcaseasaninstanceofBacon’serrors。Bacon，hesays，72*’entirelyoverlookedthePluralityofCauses。Allhisrulesimplytheassumption，socontrarytowhatwenowknowofnature，thataphenomenoncannothavemorethanonecause。’Baconwasmisguidedenoughtoapplythistoheat。Now，asMillhadalreadyargued，heatmayhaveseveralcauses：the’sun，’or’friction，’or’percussion，’or’electricity，’or’chemicalaction。’73*
Consequently，theattempttofindasinglecauseisdoomedtofailure。Weshallfind，notthatoneantecedentbut，thatoneofseveralantecedentsisalwayspresent。Clearlythe’sun’isnot’friction，’noris’percussion’’electricity。’Eachofthosephrasesindicatesconcretefactsinvolvingvariousprocesses。
Heat，asa’modeofmotion，’occursinthemall，becauseallinvolveparticularphasesofmovement。Fromthe’raw’fact，asitpresentsitself——’Thisbodyishot’——Icannotsaywhichofvariouslawsrepresentsthetrueantecedentsinthatcase。Theheatmayhavebeencausedbyexposuretofireorbyfriction。Inthatsense，undoubtedly，oneeffectmayreallyhaveanynumberof’causes。’Butreplacealltheconditions，anditisevidentthattherecanbeonlyonetrueanalysisofthewholeprocess。