逻辑错误-Logical+Fallacies

LogicalFallacies(1)LogicalFallacies(A)Source:Fowler,H.RamseyandJaneE.Aar.TheLittle,BrownHandbook.NewYork:PearsonEducation,2007.214-218.Fallacies—errorsinargument—eitherevadetheissueoftheargumentortreattheargumentasifitweremuchsimplerthanitis.EvasionsAneffectiveargumentsquarelyfacesthecentralissueorquestionitaddresses.Anineffectiveargumentmaydodgetheissueinoneofthefollowingways:•Beggingthequestion:treatinganopinionthatisopentoquestionasifitwerealreadyprovedordisproved.Thecollegelibrary’sexpensesshouldbereducedbycuttingsubscriptionstouselessperiodicals.[Beggedquestions:Aresomeofthelibrary’speriodicalsuseless?Uselesstowhom?]•onsequitur(Latin:“Itdoesnotfollow”):linkingtwoormoreideasthatinfacthavenologicalconnection.IfhighschoolEnglishwereeasier,fewerstudentswouldhavetroublewiththecollegeEnglishrequirement.[Presumably,ifhighschoolEnglishwereeasier,studentswouldhavemoretrouble.]•Redherring:introducinganirrelevantissueintendedtodistractreadersfromtherelevantissues.Acampusspeechcodeisessentialtoprotectstudents,whoalreadyhaveenoughproblemscopingwithrisingtuition.[Tuitioncostsandspeechcodesaredifferentsubjects.Whatprotectionsdostudentsneedthataspeechcodewillprovide?]•Appealtoreaders’fearorpity:substitutingemotionsforreasoning.Sheshouldnothavetopaytaxesbecausesheisanagedwidowwithnofriendsorrelatives.[Appealstopeople’spity.Shouldageandloneliness,ratherthanincome,determineaperson’staxobligation?]•Bandwagon:invitingreaderstoacceptaclaimbecauseeveryoneelsedoes.Aseveryoneknows,marijuanauseleadstoheroinaddiction.[Whatistheevidence?]LogicalFallacies(2)•Adhominem(Latin:“totheman”):attackingthequalitiesofthepeopleholdinganopposingviewratherthanthesubstanceoftheviewitself.Oneofthescientistshasbeentreatedforemotionalproblems,sohispessimismaboutnuclearwastemeritsnoattention.[Dothescientist’spreviousemotionalproblemsinvalidatehiscurrentviews?]OversimplificationsInavainattempttocreatesomethingneatlyconvincing,anineffectiveargumentmayconcealorignorecomplexitiesinoneofthefollowingways:•Hastygeneralization:makingaclaimonthebasisofinadequateevidence.Itisdisturbingthatseveraloftheyouthswhoshotupschoolswereusersofviolentvideogames.Obviously,thesegamescanbreedviolence,andtheyshouldbebanned.[Afewcasesdonotestablishtherelationbetweenthegamesandviolentbehavior.Mostyouthswhoplayviolentvideogamesdonotbehaveviolently.]•Sweepinggeneralization:makinganinsupportablestatement.Manysweepinggeneralizationsareabsolutestatementsinvolvingwordssuchasall,always,never,andnoonethatallownoexceptions.Othersarestereotypes,conventionalandoversimplifiedcharacterizationsofagroupofpeople:Peoplewholiveincitiesareunfriendly.Californiansarefad-crazy.Womenareemotional.Mencan’texpresstheirfeelings.•Reductivefallacy:oversimplifying(reducing)therelationbetweencausesandeffects.Povertycausescrime.[Ifso,thenwhydopeoplewhoarenotpoorcommitcrimes?Andwhyaren’tallpoorpeoplecriminals?]•Posthocfallacy(fromLatin,posthoc,ergopropterhoc:“afterthis,thereforebecauseofthis”):assumingthatbecauseAprecededB,thenAmusthavecausedB.Thetowncouncilerredinpermittingtheadultbookstoretoopen,forshortlyafterwardtwowomenwereassaulted.[Itcannotbeassumedwithoutevidencethatthewomen’sassailantsvisitedorwereinfluencedbythebookstore.]•Either/orfallacy:assumingthatacomplicatedquestionhasonlytwoanswers,onegoodandonebad,bothgood,orbothbad.Eitherwepermitmandatorydrugtestingintheworkplaceorproductivitywillcontinuetodecline.[Productivityisnotnecessarilydependentondrugtesting.]LogicalFallacies(3)LogicalFallacies(B)Source:Kirszner,LaurieG.andStephenR.Mandell.TheWadsworthHandbook,8thed.Beijing:ChinaReminUniversityPress,2008.121-122.HastyGeneralizationDrawingaconclusionbasedontoolittleevidenceThepersonIvotedforisnotdoingagoodjobinCongress.Therefore,votingisawasteoftime.[Onedisappointingexperiencedoesnotwarrantthestatementthatyouwillnevervoteagain.]SweepingGeneralization(OversimplifiedGeneralization)MakingageneralizationthatcannotbesupportednomatterhowmuchevidenceissuppliedEveryoneshouldexercise.[Somepeople,forexamplethosewithsevereheartconditions,mightnotbenefitfromexercise.]EquivocationShiftingthemeaningofakeywordorphraseduringanargumentItisnotinthepublicinterestforthepublictoloseinterestinpolitics.[Althoughclever,theshiftinthemeaningoftheterm“publicinterest”cloudstheissue.]onSequiturArrivingataconclusionthatdoesnotlogicallyfollowfromwhatcomebefore.KimWilliamsisagoodlawyer,soshewillmakeagoodmayor.[KimWilliamsmaybeagoodlawyer,butitdoesnotnecessarilyfollowthatshewillmakeagoodsenator.]Either/OrFallacy(FalseDilemma)TreatingacomplexissueasifithasonlytwosidesEitherweinstituteuniversalhealthcare,orthehealthofallAmericanswilldecline.[Goodhealthdoesnotnecessarilydependonuniversalhealthcare.]PostHocEstablishinganunjustifiedlinkbetweencauseandeffectTheUnitedStatessoldwheattoRussia.Thismustbewhatcausedthepriceofwheattorise.[Otherfactors,unrelatedtothesale,couldhavecausedthepriceofwheattorise.]BeggingtheQuestion(circularreasoning)StatingadebatablepremiseasifitweretrueStem-cellresearchshouldbebannedbecausenothinggoodcancomefroms