LetuspassnowtowhatIhavecalledthedutiesoftheAffections，therulesthatprescribeeitherloveitselfinsomedegree，ortheservicesthatnaturallyspringfromitinthoserelationswhereitisexpectedanddesired。Here，inthefirstplace，thequestionhowfarweareboundtorendertheseserviceswhenwedonotfeeltheaffectionisanswereddifferentlyinmanycasesbydifferentpersons，andnodeterminationofthelimitseemsself-evident。Andsimilarlyifweaskwhetheraffectionitselfisaduty；forontheonehanditisatleastonlypartiallywithinthecontrolofthewill，andinsofarasitcanbeproducedbyvoluntaryeffort，thereisthoughttobesomethingunsatisfactoryandunattractiveintheresult；andontheotherhand，incertainrelationsitseemstobecommonlyregardedasaduty。OnthosepointsthedoctrineofCommonSenseisratheraroughcompromisebetweenconflictinglinesofthoughtthancapableofbeingdeducedfromaclearanduniversallyacceptedprinciple。AndifweconfineourselvestothespecialrelationswhereCommonSenseadmitsnodoubtastothebroadmoralobligationofatleastrenderingsuchservicesasaffectionnaturallyprompts，stilltherecognisedrulesofexternaldutyintheserelationsare，inthefirstplace，wantingindefinitenessandprecision:andsecondly，theydonot，whenrigorouslyexamined，appeartobe，ortobereferableto，independentintuitionssofarastheparticularityofthedutiesisconcerned。
Letustake，forexample，thedutyofparentstochildren。Wehavenodoubtaboutthisdutyasapartofthepresentorderofsociety，bywhichtheduegrowthandtrainingoftherisinggenerationisdistributedamongtheadults。Butwhenwereflectonthisarrangementitself，wecannotseeintuitivelythatitisthebestpossible。Itmaybeplausiblymaintainedthatchildrenwouldbebettertrained，physicallyandmentally，iftheywerebroughtupunderthesupervisionofphysiciansandphilosophers，inlargeinstitutionsmaintainedoutofthegeneraltaxes。Wecannotdecideaprioriwhichofthesealternativesispreferable；wehavetorefertopsychologicalandsociologicalgeneralisations，obtainedbyempiricalstudyofhumannatureinactualsocieties。If，however，weconsiderthedutyofparentsbyitself，outofconnexionwiththissocialorder，itiscertainlynotself-evidentthatweowemoretoourownchildrenthantootherswhosehappinessequallydependsonourexertions。Togetthequestionclear，letussupposethatIamthrownwithmyfamilyuponadesertisland，whereIfindanabandonedorphan。IsitevidentthatIamlessboundtoprovidethischild，asfarasliesinmypower，withthemeansofsubsistence，thanIamtoprovideformyownchildren？Accordingtosome，myspecialdutytothelatterwouldarisefromthefactthatIhavebroughtthemintobeing:but，ifso，itwouldseemthatonthisprincipleIhavearighttodiminishtheirhappiness，providedIdonotturnitintoanegativequantity；since，aswithoutmetheywouldnothaveexistedatall，theycan，asmychildren，havenoclaimuponmeformorethananexistenceonthewholeabovezeroinrespectofhappiness。Wemightevendeduceaparentalrightsofarasthisspecialclaimisconcernedtoextinguishchildrenpainlesslyatanypointoftheirexistence，ifonlytheirlifeuptothatpointhasbeenonthewholeworthhaving；forhowcanpersonswhowouldhavehadnolifeatallbutformefairlycomplainthattheyarenotallowedmorethanacertainquantity？[1]IdonotmeantoassertthatthesedoctrinesareevenimplicitlyheldbyCommonSense:butmerelytoshowthathere，aselsewhere，thepursuitofanirrefragableintuitionmayleadusunawareintoanestofparadoxes。
Itseems，then，thatwecannot，afterall，saythatthespecialdutyofparentstochildren，consideredbyitself，possessesclearself-evidence:anditwaseasytoshowcf。chap。iv。thatasrecognisedbyCommonSenseitslimitsareindeterminate。
Theruleprescribingthedutyofchildrentoparentsneednotdetainus；fortoCommonSenseitcertainlyseemsdoubtfulwhetherthisisnotmerelyaparticularcaseofgratitude；
andwecertainlyhavenoclearintuitionofwhatisduetoparentswhodonotdeservegratitude。Again，themoralrelationofhusbandandwifeseemstodependchieflyuponcontractanddefiniteunderstanding。Itis，nodoubt，usuallythoughtthatMorality，aswellaslawprescribescertainconditionsforallconnubialcontracts:andinourownageandcountryitisheldthattheyshouldbe1monogamicand2permanent。Butitseemsclearthatneitheroftheseopinionswouldbemaintainedtobeaprimaryintuition。WhethertheseoranyotherlegalregulationsoftheunionofthesexescanbededucedfromsomeintuitiveprincipleofPurity，wewillpresentlyconsider:butasforsuchconjugaldutiesasarenotprescribedbyLaw，probablynooneatthepresentdaywouldmaintainthatthereisanysuchgeneralagreementastowhattheseare，aswouldsupportthetheorythattheymaybeknownapriori。[2]