Thelastsentencesuggestsonemoreexplanation，which，forclearness’sake，itseemsdesirabletomake:anexplanation，however，ratheroftheplanandpurposeofthepresenttreatisethanofthenatureandboundariesofthesubjectofEthicsasgenerallyunderstood。
Thereareseveralrecognisedwaysoftreatingthissubject，noneofwhichIhavethoughtitdesirabletoadopt。Wemaystartwithexistingsystems，andeitherstudythemhistorically，tracingthechangesinthoughtthroughthecenturies，orcompareandclassifythemaccordingtorelationsofresemblance，orcriticisetheirinternalcoherence。
Orwemayseektoaddtothenumberofthesesystems:andclaimaftersomanyunsuccessfuleffortstohaveatlastattainedtheonetruetheoryofthesubject，bywhichallothersmaybetested。Thepresentbookcontainsneithertheexpositionofasystemnoranaturalorcriticalhistoryofsystems。IhaveattemptedtodefineandunfoldnotoneMethodofEthics，butseveral:atthesametimethesearenotherestudiedhistorically，asmethodsthathaveactuallybeenusedorproposedfortheregulationofpractice；butratherasalternativesbetweenwhich——sofarastheycannotbereconciled——thehumanmindseemstomenecessarilyforcedtochoose，whenitattemptstoframeacompletesynthesisofpracticalmaximsandtoactinaperfectlyconsistentmanner。Thus，theymightperhapsbecallednaturalmethodsrationalised；becausemencommonlyseemtoguidethemselvesbyamixtureofdifferentmethods，moreorlessdisguisedunderambiguitiesoflanguage。Theimpulsesorprinciplesfromwhichthedifferentmethodstaketheirrise，thedifferentclaimsofdifferentendstoberational，areadmitted，tosomeextent，byallminds:andasalongwiththeseclaimsisfelttheneedofharmonisingthem——sinceitis，aswassaid，apostulateofthePracticalReason，thattwoconflictingrulesofactioncannotbothbereasonable——theresultisordinarilyeitheraconfusedblending，oraforcedandprematurereconciliation，ofdifferentprinciplesandmethods。
Norhavethesystemsframedbyprofessedmoralistsbeenfreefromsimilardefects。Thewritershaveusuallyproceededtosynthesiswithoutadequateanalysis；thepracticaldemandfortheformerbeingmoreurgentlyfeltthanthetheoreticalneedofthelatter。ForhereasinotherpointsthedevelopmentofthetheoryofEthicswouldseemtobesomewhatimpededbythepreponderanceofpracticalconsiderations；andperhapsamorecompletedetachmentofthetheoreticalstudyofrightconductfromitspracticalapplicationistobedesiredforthesakeevenofthelatteritself:sinceatreatmentwhichisacompoundbetweenthescientificandthehortatoryisapttomissboththeresultsthatitwouldcombine；themixtureisbewilderingtothebrainandnotstimulatingtotheheart。Soagain，Iaminclinedtothinkthathere，asinothersciences，itwouldbeanadvantagetodrawasdistinctalineaspossiblebetweentheknownandtheunknown；astheclearindicationofanunsolvedproblemisatanyrateasteptoitssolution。
Inethicaltreatises，however，therehasbeenacontinualtendencytoignoreandkeepoutofsightthedifficultiesofthesubject；eitherunconsciously，fromalatentconvictionthatthequestionswhichthewritercannotanswersatisfactorilymustbequestionswhichoughtnottobeasked；orconsciously，thathemaynotshaketheswayofmoralityoverthemindsofhisreaders。