Chapter-4-Presupposition-and-entailment(课堂PPT)

1Chapter4PresuppositionandentailmentNowwelookattwokindsofinference.Entailmentemphasizestherelationshipbetweensentencesthatformsthebasisforsomeotherinferences.Presuppositionemphasizestheinferencethatismorecontext-dependent.2Presuppositionandentailmentaretechnicaltermsusedtodescribetwodifferentaspectsoftheinformationthatspeakersassumethatlistenersalreadyknow.3Presuppositionissomethingthespeakerassumestobethecasepriortomakinganutterance.Speakers,notsentences,havepresuppositions.Entailmentissomethingthatlogicallyfollowsfromwhatisassertedintheutterance.Sentences,notspeakers,haveentailments.4PresuppositionIntheUSA,anaccusedmuggerratherfoolishlychosetodefendhimselfatthetrial.Thefollowingisoneofthequestionsheputtohisvictim.DidyougetagoodlookatmyfacewhenItookyourpurse?Whydoyouthinktheaccusedmuggerissofoolish?5PresuppositionLookattherelationshipbetweenthefollowingtwopropositions.a.Mary’sdogiscut.(=p)b.Maryhasadog.(=q)c.pq(ppresupposesq)a.Mary’sdogisn’tcute.(=NOTp)b.Maryhasadog.(=q)c.NOTpq6Presuppositiona.EverybodyknowsthatJohnisgay.(=p)b.Everybodydoesn’tknowthatJohnisgay.(=NOTp)c.Johnisgay.(=q)d.pq&NOTpqConstancyundernegation:Thepresuppositionofastatementwillremainconstant(i.e.stilltrue)evenwhenthatstatementisnegated.7TypesofpresuppositiontriggerLexicalExamplesExistential’s,the,that,this,these,those…factiveRealize,regret,know…NonfactiveDream,imagine,pretend…StructuralExamples“if”conditionalstructureIfyouweremyfriend,youwouldhavehelpedme.Youarenotmyfriend.Wh-question/subordinateclauseWhendidheleave?Heleft.8TypesofpresuppositiontriggerDecidewhichonescontainthepresuppositionthatatthetimetheutterancewasmade“Therewasachocolatecake”.Whatdothoseutteranceshaveincommon?1.(a)Mikemightfindthechocolatecakeinthekitchen.(b)Mikemightfindachocolatecakeinthekitchen.2.(a)IsMikegivingAnniethatchocolatecake?(b)IsMikegivingAnnieachocolatecake?3.(a)DidMikehideachocolatecake?(b)DidMikehideAnnie’schocolatecake?9TypesofpresuppositiontriggerShedidn’trealizehewasill.(Hewasill.)Iwasn'tawarethatshewasmarried.(Shewasmarried.)IdreamedthatIwasrich.(Iwasnotrich.)Ifyouweremyfriend,youwouldhavehelpedme.(Youarenotmyfriend.)10TypesofpresuppositiontriggerDecidewhichonescontainthepresuppositionthat“Mikesmashedthetelevision”.Whatdothoseutteranceshaveincommon?a.DidMikesmashthetelevision?b.WhendidMikesmashthetelevision?c.IwaseatingpopcornwhenMikesmashedthetelevision.d.WhydidMikesmashthetelevision?e.Idon’tunderstandwhyMikesmashedthetelevision.f.IwonderifMikesmashedthetelevision.g.IwonderhowMikesmashedthetelevision.11Theprojectionproblemseepp30-31[12][14]Themeaningofsomepresuppositions(asparts)doesn’tsurvive(project)tobecomethemeaningofsomecomplexsentences(aswholes).Howtoexplaintheprojectionproblem?Itisdestroyedbyentailment.Theentailment(anecessary/logicalconsequenceofwhatissaid)issimplymorepowerfulthanthepresupposition(anearlierassumption).12TheprojectionproblemThepowerofentailmentcanalsobeusedtocancelexistentialpresupposition.a.TheKingofEnglandvisitedus.(theexistenceofking)b.TheKingofEnglanddoesn’texist!(‖-Thereisnotaking.)Thepresuppositionof“theexistenceofking”iscancelledbytheentailmentofb.13SummaryWehavedescribedpresuppositionsasinferencesaboutwhatisassumedinanutteranceratherthandirectlyasserted.Presuppositionsarecloselylinkedtothewordsandgrammaticalstructuresthatareactuallyusedintheutteranceandourknowledgeaboutthewaylanguageusersconventionallyinterpretthem.Presuppositionscanbecancelledbyentailment.14EntailmentSupposethatsentence(a)ineachpairistrue.Thenlookatsentence(b)anddecideifyoucanassumethatitisautomaticallytrue.1.(a)Anniecaughtatrout.(b)Anniecaughtafish.2.(a)Annieisthin.(b)Annieisnotfat.3.(a)Anniebakedacake.(b)Anniebakedsomething.15EntailmentOncesentence(a)istrue,sentence(b)becomesautomaticallytrue.Sentence(b)isanentailmentofsentence(a).Thiskindofinferenceis“forfree”.Itrequiresonlyaknowledgeofthesemantics.Trout/fish,thin/fat,cake/something.16OrderedentailmentsOneutterancemayinvolveverylargenumberofbackgroundentailments.Thespeakerwillindicatehowtheseentailmentsaretobeordered.Thespeakerwillcommunicatebystress,whichentailmentisassumedtobeintheforeground.a.RoverchasedTHREEsquirrels.(threeisforegrounded.)b.ROVERchasedthreeaquirrels.(ROVERisforegrounded.)17OrderedentailmentsUsing“it-cleft”constructionThisisparticularlyusefulinwrittenlanguagewherestressisnotavailable.a.ThePAINTERSbrokethewindow.(spoken)b.Itwasthepainterswhobrokethewindow.(written)Whenthecleftconstructionisusedinspokenlanguagecombinedwithheavystress,someinterestingmeaningdifferencescanemerge.Compare:a.Itwasn'tMEwhoburntthetoast.(itisanybodyelse…)b.ItWANSN’Tmewhoburntthetoast.(Itwasme…)18SummaryAllsentenceshaveanumberofentailments---othersentenceswhichareautomaticallytrueiftheoriginalsentenceistrue.Entailmentsareinferencesthatcanbedrawnsolelyfromourknowledgeabutthesemanticrelationshipinalanguage.Thisknowledgeallowsustocommunicatemuchmorethanweactually“say”.19ExercisesHerearethreedifferentstresspatternsforAnnieruinedthesweater.Trytotellwhich