Is，then，thisobligationintuitivelyseentobeindependentandcertain？
Itisoftensaidtobeso:andperhapswemaysaythatitseemssotounreflectivecommonsense。Butreflectionseemsatleasttodiscloseaconsiderablenumberofqualificationsoftheprinciple；
someclearandprecise，whileothersaremoreorlessindefinite。
Inthefirstplace，thoughtfulpersonswouldcommonlyadmitthattheobligationofapromiseisrelativetothepromisee，andmaybeannulledbyhim。Andthereforeifthepromiseebedead，orotherwiseinaccessibleandincapableofgrantingrelease，thereisconstitutedanexceptionalcase，ofwhichthesolutionpresentssomedifficulty。[1]
Secondly，apromisetodoanimmoralactisheldnottobebinding，becausethepriorobligationnottodotheactisparamount；justasinlawacontracttodowhatamanisnotlegallyfreetodo，isinvalid:otherwiseonecouldevadeanymoralobligationbypromisingnottofulfilit，whichisclearlyabsurd。[2]
Andthesameprincipleisofcourseapplicabletoimmoralomissionsorforbearancestoact:herehowever，acertaindifficultyarisesfromthenecessityofdistinguishingbetweendifferentkindsordegreesofobligatorinessinduties；sinceitisclearthatapromisemaysometimesmakeitobligatorytoabstainfromdoingwhatitwouldotherwisehavebeenadutytodo。ThusitbecomesmydutynottogivemoneytoameritorioushospitalifIhavepromisedallIcansparetoanundeservingfriend；thoughapartfromthepromiseitmighthavebeenmydutytopreferthehospitaltothefriend。
Wehave，however，alreadyseenthedifficultyofdefiningthelimitsofstrictdutyinmanycases:thuse。g。itmightbedoubtedhowfarthepromiseofaidtoafriendoughttooverridethedutyofgivingone’schildrenagoodeducation。Theextent，therefore，towhichtheobligationofapromiseoverridespriorobligationsbecomespracticallysomewhatobscure。
Furtherqualificationsofthedutyoffidelitytopromises，theconsiderationofwhichisinvolvedinmoredifficultyanddispute，aresuggestedwhenweexaminemorecloselytheconditionsunderwhichpromisesaremade，andtheconsequencesofexecutingthem。Inthefirstplace，itismuchdisputedhowfarpromisesobtainedby`fraudorforce’arebinding。Asregardsfraud，ifthepromisewasunderstoodtobeconditionalonthetruthofastatementwhichisfoundtobefalse，itisofcoursenotbinding，accordingtotheprincipleIoriginallylaiddown。Butapromisemaybemadeinconsequenceofsuchafraudulentstatement，andyetmadequiteunconditionally。Evenso，ifitwereclearlyunderstoodthatitwouldnothavebeenmadebutforthefalsestatement，probablymostpersonswouldregarditasnotbinding。Butthefalsestatementmaybeonlyoneconsiderationamongothers，anditmaybeofanydegreeofweight；anditseemsdoubtfulwhetherweshouldfeeljustifiedinbreakingapromise，becauseasinglefraudulentstatementhadbeenapartoftheinducementtomakeit:stillmoreiftherehasbeennoexplicitassertion，butonlyasuggestionofwhatisfalse:ornofalsehoodatall，statedorsuggested，butonlyaconcealmentofmaterialcircumstances。Wemayobservethatcertainkindsofconcealmentaretreatedaslegitimatebyourlaw:inmostcontractsofsale，forexample，thelawadoptstheprincipleof’caveatemptor’，anddoesnotrefusetoenforcethecontractbecausethesellerdidnotdisclosedefectsinthearticlesold，unlessbysomewordsoractsheproducedthebeliefthatitwasfreefromsuchdefects。
Still，thisdoesnotsettlethemoralquestionhowfarapromiseisbindingifanymaterialconcealmentisshowntohavebeenusedtoobtainit。Wehavealsotoconsiderthecaseinwhichanerroneousimpressionhasnotbeenwilfullyproduced，butwaseithersharedbythepromiseeorproducedinsomewayunintentionally。Perhapsinthislastcasemostwouldsaythatthebindingnessofthepromiseisnotaffected，unlessitwasexpresslyconditional。ButonallthesepointsCommonSenseseemsdoubtful:andsomewhatsimilardifficultiespresentthemselveswhenweendeavourtodefinetheobligationofpromisespartlyobtainedbysomedegreeofillegalviolenceandintimidation。
But，secondly，evenifapromisehasbeenmadequitefreelyandfairly，circumstancesmayaltersomuchbeforethetimecomestofulfilitthattheeffectsofkeepingitmaybequiteotherthanthosewhichwereforeseenwhenitwasmade。Insuchacaseprobablyallwouldagreethatthepromiseeoughttoreleasethepromiser。Butifhedeclinestodothis，itseemsdifficulttodecidehowfarthelatterisbound。Somewouldsaythatheisinallcases:whileotherswouldconsiderthataconsiderablealterationofcircumstancesremovedtheobligation——perhapsaddingthatallengagementsmustbeunderstoodtobetakensubjecttoageneralunderstandingthattheyareonlybindingifmaterialcircumstancesremainsubstantiallythesame。Butsuchaprincipleverymuchimpairsthetheoreticaldefinitenessoftheduty。
Thisdifficultyassumesanewaspectwhenweconsiderthecasealreadynoticed，ofpromisesmadetothosewhoarenowdeadortemporarilyoutofthereachofcommunications。Forthenthereisnomeansofobtainingreleasefromthepromise，whileatthesametimeitsperformancemaybereallyopposedtothewishes——orwhatwouldhavebeenthewishes——ofbothparties。Thedifficultyissometimesconcealedbysayingthatitisourdutytocarryoutthe`intention’ofthepromise。ForassousedthewordIntentionis，incommonparlance，ambiguous:itmayeithermeanthesignificationwhichthepromiseeattachedtothetermsemployed，asdistinctfromanyothersignificationwhichthecommonusageofwordsmightadmit:
oritmayincludeulteriorconsequencesoftheperformanceofthepromise，whichhehadinviewinexactingit。Nowwedonotcommonlythinkthatthepromiserisconcernedwiththelatter。Hecertainlyhasnotpledgedhimselftoaimgenerallyattheendwhichthepromiseehasinview，butonlysofarassomeparticularmeansareconcerned:andifheconsidersthesemeansnotconducivetotheend，beisnottherebyabsolvedfromhispromise，underordinarycircumstances。Butinthecasesupposed，whencircumstanceshavemateriallychanged，andthepromisedoesnotadmitofrevision，probablymostpersonswouldsaythatweoughttotakeintoconsiderationtheulteriorwishesofthepromisee，andcarryoutwhatwesincerelythinkwouldhavebeenhisintention。Buttheobligationthusbecomesveryvague:sinceitisdifficulttotellfromaman’swishesunderonesetofcircumstanceswhathewouldhavedesiredundercircumstancesvaryingfromtheseinacomplexmanner:andpracticallythisviewoftheobligationofapromisegenerallyleadstogreatdivergenceofopinion。Henceitisnotsurprisingthatsomeholdthateveninsuchacasetheobligationoughttobeinterpretedstrictly:whileothersgototheotherextreme，andmaintainthatitceasesaltogether。
Butagainitwassaidthatapromisecannotabrogateapriorobligation；and，asaparticularapplicationofthisrule，itwouldbegenerallyagreedthatnopromisecanmakeitrighttoinflictharmonanyone。Onfurtherconsideration，however，itappearsdoubtfulhowfarthepersonsbetweenwhomthepromisepassedareincludedinthescopeofthisrestriction。For，first，itdoesnotseemtobecommonlyheldthatamanisasstrictlyboundnottoinjurehimselfasheistoavoidharmingothers；andsoitisscarcelythoughtthatapromiseisnotbindingbecauseitwasafoolishone，andwillentailanamountofpainorburdenonthepromiseroutofproportiontothegooddonetothepromisee。Still，ifwetakeanextremecase，wherethesacrificeisverydisproportionatetothegain，manyconscientiouspersonswouldthinkthatthepromiseoughtrathertobebrokenthankept。And，secondly，adifferentquestionariseswhenweconsiderthepossibilityofinjuringthepromiseebyfulfillingthepromise。Forwhenitissaidtobewrongtodoharmtoanyone，wedonotcommonlymeanonlywhathethinksharm，butwhatreallyisso，thoughhemaythinkitabenefit；foritseemsclearlyacrimeformetogiveanyonewhatIknowtobepoison，eventhoughhemaybestubbornlyconvincedthatitiswholesomefood。ButnowsupposethatIhavepromisedAtodosomethingwhich，beforeIfulfilthepromise，Iseereasontoregardaslikelytoinjurehim。Thecircumstancesmaybepreciselythesame，andonlymyviewofthemhavechanged。IfAtakesadifferentviewandcallsonmetofulfilthepromise，isitrighttoobeyhim？Surelynoonewouldsaythisinanextremecase，suchasthatofthepoison。Butiftheruledoesnotholdforanextremecase，wherecanwedrawtheline？atwhatpointoughtItogiveupmyjudgmenttoA，unlessmyownconvictionisweakened？CommonSenseseemstogivenoclearanswer。
1havelaiddownthatapromiseisbindinginsofarasitisunderstoodonbothsidessimilarly:andsuchanunderstandingisordinarilyattainedwithsufficientclearness，asfarastheapprehensionofexpresswordsorsignsisconcerned。Still，evenhereobscurityandmisapprehensionsometimesoccur；andinthecaseofthetacitunderstandingswithwhichpromisesareoftencomplicated，alackofdefiniteagreementisnotimprobable。Itbecomes，therefore，ofpracticalimportancetodecidethequestionpreviouslyraised:Whatdutyrestsonthepromiserofsatisfyingexpectationswhichhedidnotintendtocreate？IcalledthisadutynotsomuchofGoodFaithasofJustice，whichprescribesthefulfilmentofnormalexpectations。Howthenshallwedeterminewhattheseare？Themethodbywhichwecommonlyascertainthemseemstobethefollowing。Weformtheconceptionofanaverageornormalman，andconsiderwhatexpectationshewouldformunderthecircumstances，inferringthisfromthebeliefsandexpectationswhichmengenerallyentertainundersimilarcircumstances。
Werefer，therefore，tothecustomaryuseoflanguage，andcustomarytacitunderstandingscurrentamongpersonsintheparticularrelationsinwhichpromiserandpromiseestand。Suchcustomaryinterpretationsandunderstandingsareofcoursenotobligatoryuponpersonsenteringintoanengagement:
buttheyconstituteastandardwhichwethinkwemaypresumetobeknowntoallmen，andtobeacceptedbythem，exceptinsoforasitisexplicitlyrejected。Ifoneofthepartiestoanengagementhasdeviatedfromthiscommonstandardwithoutgivingexpressnotice，wethinkitrightthatlieshouldsufferanylossthatmayresultfromthemisunderstanding。Thiscriterionthenisgenerallyapplicable:butifcustomisambiguousorshiftingitcannotbeapplied；andthenthejustclaimsofthepartiesbecomeaproblem，thesolutionofwhichisverydifficult，ifnotstrictlyindeterminate。
Sofarwehavesupposedthatthepromisercanchoosehisownwords，andthatifthepromiseefindsthemambiguousbecangetthemmodified，orwhatcomestothesamethingexplained，bythepromiser。
Butwehavenowtoobservethatinthecaseofpromisesmadetothecommunity，asaconditionofobtainingsomeofficeoremolument，acertainunalterableformofwordshastobeusedifthepromiseismadeatall。Herethedifficultiesofmoralinterpretationaremuchincreased。Itmaybesaid，indeed，thatthepromiseoughttobeinterpretedinthesenseinwhichitstermsareunderstoodbythecommunity:and，nodoubt，iftheirusageisquiteuniformandunambiguous，thisruleofinterpretationissufficientlyobviousandsimple。Butsincewordsareoftenusedindifferentwaysbydifferentmembersofthesamesociety，andespeciallywithdifferentdegreesofstrictnessandlaxity，itoftenhappensthatapromisetothecommunitycannotstrictlybesaidtobeunderstoodinanyonesense:thequestionthereforearises，whetherthepromiserisboundtokeepitinthesenseinwhichitwillbemostcommonlyinterpreted，orwhetherhemayselectanyofitspossiblemeanings。Andiftheformulaisoneofsomeantiquity，itisfurtherquestioned，whetheritoughttobeinterpretedinthesensewhichitswordswouldnowgenerallybear，orinthatwhichtheyborewhenitwasdrawnup；or，iftheywerethenambiguous，inthesensewhichappearstohavebeenattachedtothembythegovernmentthatimposedthepromise。OnallthesepointsitisdifficulttoelicitanyclearviewfromCommonSense。Andthedifficultyisincreasedbythefactthatthereareusuallystronginducementstomaketheseformalengagements，whichcauseeventolerablyconscientiouspersonstotaketheminastrainedandunnaturalsense。Whenthishasbeendonecontinuallybymanypersons，anewgeneralunderstandinggrowsupastothemeaningoftheengagements:sometimestheycometoberegardedas`mereforms’，or，iftheydonotreachthispointofdegradation，theyareatleastunderstoodinasensedifferingindefinitelyfromtheiroriginalone。Thequestionthenarises，bowfarthisprocessofgradualillegitimaterelaxationorperversioncanmodifythemoralobligationofthepromiseforathoroughlyconscientiousperson。Itseemsclearthatwhentheprocessiscomplete，wearerightinadoptingthenewunderstandingsofarasGoodFaithisconcerned，evenifitpalpablyconflictswiththenaturalmeaningoflanguage；althoughitisalwaysdesirableinsuchcasesthattheformofthepromiseshouldbechangedtocorrespondwiththechangedsubstance。
Butwhen，asisordinarilythecase，theprocessisincomplete，sinceaportionofthecommunityunderstandstheengagementintheoriginalstrictsense，theobligationbecomesdifficulttodetermine，andthejudgmentsofconscientiouspersonsrespectingitbecomedivergentandperplexed。
Tosumuptheresultsofthediscussion:itappearsthataclearconsensuscanonlybeclaimedfortheprinciplethatapromise，expressortacit，isbinding，ifanumberofconditionsarefulfilled:viz。ifthepromiserhasaclearbeliefastothesenseinwhichitwasunderstoodbythepromisee，andifthelatterisstillinapositiontograntreleasefromit，butunwillingtodoso，ifitwasnotobtainedbyforceorfraud，ifitdoesnotconflictwithdefinitepriorobligations，ifwedonotbelievethatitsfulfilmentwillbeharmfultothepromisee，orwillinflictadisproportionatesacrificeonthepromiser，andifcircumstanceshavenotmateriallychangedsinceitwasmade。Ifanyoftheseconditionsfails，theconsensusseemstobecomeevanescent，andthecommonmoralperceptionsofthoughtfulpersonsfallintoobscurityanddisagreement。