Mill’sinsistenceuponthisimaginary’pluralityofcauses’
issignificant。Itindicatestheprecisestageinthedevelopmentoftheideaofcausetowhichhisdoctrinecorresponds。Takingwhatwemaycallthepopularsenseofcausation，the’plurality’
expressesanobvioustruth；andwecanunderstanditsplausibility。Wetake，infact，twoconcreteeventswhichfolloweachother，andcallthemcauseandeffect。Weuseatool——aknifetocutbread，forexample；weareforcedtoattendtothefactthateverydifferenceintheknifewillhaveaneffectontheresult。Theworkisbetterorworse，astheknifeissharperorblunter。Ifwedidnotrecognisethisineverypurposefulaction，allactionwouldbeintrinsicallyuncertain。Weare，therefore，impressedwiththenecessityofadmittingthattheeffectisdeterminedbythecause。But，ontheotherhand，theknifeisthere。Itmayhavebeenmadebyfiftydifferentmethods，andyetbethesame。Thehandlemayhavebeenfirstmadeandthentheblade，orviceversa，andsoforth。thereforewebelieve，andinthissenseofcausebelievecorrectly，thatoneeffectmaybetheproductofanynumberofdifferent’causes。’Inordertoreachthemorescientificsenseofcausation，wehavetotakeintoaccountallthatwehaveneglected。Theknifeisoneproductofanindefinitemultitudeofprocesses，andisthereforenotthetotal’effect’oftheconcreteantecedent，butonlyapartofitarbitrarilysingledout。Wedonotattendtoallthesecollateralresults，becauseforusatthemomenttheyhavenointerest；butwhenwesystematicallycarryoutthe’uniformityofnature’
principle，itisobviousthattheymustbetakenintoaccount。Wethenseethatalthoughpreciselysimilarproductsappearinaninfinitevarietyofconcreteprocesses，theycorrespondonlytoapartofthoseprocesses，andmayalwaysbeanalysedintoidenticalelements。Theeffectcannomorehavetwocausesthanacausetwoeffects，forcauseandeffectaredistinguishedbyobservingthesameprocessinadifferentorder。Itwasjustbecausemenofscienceheldthattheoneeffectmusthaveonecausethattheycouldmakeacoherenttheoryofheat。Mill，howevergoesastepfurther。Bacon’serrorwastheassumptionthattherewasonlyone’form’ofheat。Nowitisspeciallyfutile，saysMill，toseekforthecausesof’sensiblequalitiesofobjects……Inregardtoscarcelyanyofthemhasitbeenfoundpossibletotraceanyunityofcause。’Bacon，therefore，wasseekingfor’whatdidnotexist，’andtothisMilladdsthesurprisingstatementthat’thephenomenonofwhichhesoughtfortheonecausehasoftenestnocauseatall，and，whenithas，dependsasfarashithertoascertainedonanunassignablevarietyofcauses。’74*
ToexplainthisratherstartlingassertionwemusttakeonemoreofMill’stheories。Howfromthedoctrine，whichhefullyadmits，thateveryeventhasacausecanhereachtheconclusionthatsomethingshave’nocauseatall’？Oncemorewehave，I