Before，however，weattempttodefineparticularvirtuesordepartmentsofduty，itwillbewelltoexaminefurtherthenotionsofDutyandVirtueingeneral，andtherelationsbetweenthetwo，aswefindthemimplicitlyconceivedbythecommonsenseofmankind，whichweareendeavouringtoexpress。HithertoIhavetakenDutytobebroadlyconvertiblewithRightconduct:Ihavenoticed，however，thattheformerterm——like``ought’’and``moralobligation’’——impliesatleastthepotentialpresenceofmotivespromptingtowrongconduct；andisthereforenotapplicabletobeingstowhomnosuchconflictofmotivescanbeattributed。ThusGodisnotconceivedasperformingduties，thoughHeisconceivedasrealisingJusticeandotherkindsofRightnessinaction。Forasimilarreason，wedonotcommonlyapplytheterm`duty’torightactions——howevernecessaryandimportant——whenwearesostronglyimpelledtothembynon-moralinclinationsthatnomoralimpulseisconceivedtobenecessaryfortheirperformance。
Thuswedonotsaygenerallythatitisadutytoeatanddrinkenough:
thoughwedooftensaythistoinvalidswhohavelosttheirappetite。WeshouldthereforeperhapskeepmostclosetousageifwedefinedDutiesas`thoseRightactionsorabstinences，fortheadequateaccomplishmentofwhichamoralimpulseisconceivedtobeatleastoccasionallynecessary’。
Butasthislineofdistinctionisvague，andcontinuallyvarying，Ishallnotthinkitnecessarytodrawattentiontoitinthedetaileddiscussionofduties:itseemssufficienttopointoutthatweshallbechieflyconcernedwithsuchrightconductascomeswithinthedefinitionjustsuggested。
Itmaybesaid，however，thatthereisanotherimplicationintheterm``duty’’whichIhavesofaroverlooked，butwhichitsderivation-andthatoftheequivalentterm`obligation’plainlyindicates: