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1、11BasicConcepts1.1Arguments,Premises,andConclusionsLogicmaybedefinedastheorganizedbodyofknowledge,orscience,thatevaluatesarguments.Allofusencounterargumentsinourday-to-dayexperience.Wereadtheminbooksandnewspapers,hearthemontelevision,andformulatethemwhencommunicat-ingwithfriendsa
2、ndassociates.Theaimoflogicistodevelopasystemofmethodsandprinciplesthatwemayuseascriteriaforevaluatingtheargumentsofothersandasguidesinconstructingargumentsofourown.Amongthebenefitstobeexpectedfromthestudyoflogicisanincreaseinconfidencethatwearemakingsensewhenwecriticizetheargument
3、sofothersandwhenweadvanceargumentsofourown.Anargument,asitoccursinlogic,isagroupofstatements,oneormoreofwhich(thepremises)areclaimedtoprovidesupportfor,orreasonstobelieve,oneoftheothers(theconclusion).Allargumentsmaybeplacedinoneoftwobasicgroups:thoseinwhichthepremisesreallydosu
4、pporttheconclusionandthoseinwhichtheydonot,eventhoughtheyareclaimedto.Theformeraresaidtobegoodarguments(atleasttothatextent),thelatterbadarguments.Thepurposeoflogic,asthesciencethatevaluatesarguments,isthustodevelopmethodsandtechniquesthatallowustodistinguishgoodargumentsfrombad
5、.Asisapparentfromtheabovedefinition,theterm‘‘argument’’hasaveryspecificmean-inginlogic.Itdoesnotmean,forexample,amereverbalfight,asonemighthavewithone’sparent,spouse,orfriend.Letusexaminethefeaturesofthisdefinitioningreaterdetail.Firstofall,anargumentisagroupofstatements.Astatementi
6、sasentencethatiseithertrueorfalse—inotherwords,typicallyadeclarativesentenceorasentencecom-ponentthatcouldstandasadeclarativesentence.Thefollowingsentencesarestatements:Aluminumisattackedbyhydrochloricacid.BroccoliisagoodsourceofvitaminA.ArgentinaislocatedinNorthAmerica.Napoleon
7、prevailedatWaterloo.RembrandtwasapainterandShelleywasapoet.Thefirsttwostatementsaretrue,thesecondtwofalse.Thelastoneexpressestwostatements,bothofwhicharetrue.Truthandfalsityarecalledthetwopossibletruth112BasicConceptsvaluesofastatement.Thus,thetruthvalueofthefirsttwostatementsistr
8、ue,thetruthvalueofthesecondtwoisfalse,andthetru
