第五章Meaning（课堂PPT）

1,ChapterFiveMeaning,2,Meaninghasbeenstudiedforthousandsofyearsbyphilosophers,logiciansandlinguists.E.g.Plato(2)writesredredeyes:whiteofeyesisredblueeyes:irisisblue,51,9.PropositionalLogic,Truthcondition:conditionswhichmustholdforthesentencetobeusedtomakeatruestatement(atleastifitisusedliterally).Thus,beforewecantruthfullysay,onsomeoccasion,Thecatisonthemat,theremustbesomerelevantfelineoccupyingaspecificpositionrelativetoanappropriateitemoffloorcovering.,52,Thoseaspectsofthemeaningofasentencewhichdetermineitstruthconditionsarecollectivelyknownasthepropositionalcontentofthesentence.Twosentenceswithidenticalpropositionalcontentwillyieldstatementswiththesametruthvaluesonalloccasionsofuse,asforinstance,JohncaressedMaryandMarywascaressedbyJohn.Bythesametoken,iftwosentenceshavedifferentpropositionalcontent,therewillnecessarilyexistsomeconceivablesituationinwhichtheywillyieldstatementswithoppositetruthvalues.,53,Proposition:astatement,withatruthvalue(trueorfalse),egTheearthisflat.Theearthgoesaroundthesun.Allteachersarefemale.,54,9.1Logicalrelations,Not/:PAnd:PQOr:PQ,PQIfthen:PQEqualsto:PQ,55,Truthvalue:Not,56,Truthvalue:And,57,Truthvalue:Or:PQ,58,Truthvalue:Or:PQ,59,Truthvalue:Ifthen,60,Truthvalue:Equalsto,61,9.2PredicateLogic,ArgumentandPredicateJohnruns.runs(John)orR(j)JohnlovesMary.loves(John,Mary)orL(j,m)JohngaveMaryabook.gave(John,Mary,book)orG(j,m,b),62,One-placepredicate:runTwo-placepredicate:loveThree-placepredicate:give,63,Quantifiers:all,someAllteachersarefemale.x(T(x)F(x)=Forallx,ifxisateacher,xisfemale.Someteachersarefemale.x(T(x)F(x)=Therearesomexsthatarebothteachersandf