210Validity.html

Whether an argument is valid has nothing to do with whether any of it's premises are actually true. 10. No sound deductive argument has a false premise. B. Philosophy210: PracticeWith Validity       NOTE: Theanswerstotheexercisesare givenbelow. A. UNDERSTANDINGDEDUCTIVEARGUMENTS Using thedefinitionsof'deductive', 'inductive', 'valid','invalid','sound','unsound','strong',and'weak'givenin class, indicatewhetherthefollowingaretrueorfalse. 1.A deductiveargumentcanhaveall falsepremises. 2.A deductiveargumentcanhavefalse premises andatrueconclusion. 3.A validdeductiveargumentcanhave allfalse premises. 4. Aninvaliddeductiveargumentcan haveall falsepremisesandatrueconclusion. 5.A validdeductiveargumentcannot haveall falsepremisesandatrueconclusion. 6. Noinductiveargumentsarevalid. 7. Nodeductiveargumentsarestrong. 8.A validdeductiveargumentcanhave allfalse premisesandafalseconclusion. 9. Whetheranargumentisvalidhas nothingto dowithwhetheranyofit'spremisesareactuallytrue. 10. Nosounddeductiveargumenthasa falsepremise. B. EVALUATINGDEDUCTIVEARGUMENTS Relying onyournaturalsenseofwhat follows fromvariousstatementsandyourcommonsenseknowledgeoftheworld, determine foreachofthefollowingarguments(1)whetherthepremisesaretrue, (2)whethertheargumentisvalidorinvalidand(3)whetherthe argument issoundorunsound. 1. P1TherearebananastandsinBolivia andAfghanistan. C ThereisanAfghanistanbananastand. 2. P1AlaskaisbiggerthanNewYork state. P2 NewYorkstateisbiggerthanRhode Island. C AlaskaisbiggerthanRhodeIsland. 3. P1Ifpeoplefindsomething offensive,then it'simmoral. P2 Peoplefindhomosexualityoffensive. C Homosexualityisimmoral. 4. P1SomeAlbanianshailfromAlbania. C WealthyAlbanianshailfromAlbania 5. P1BarryLarkinplaysfortheReds. P2 MarkMcGuireplaysfortheCardinals. C TheRedsandtheCardinalsarebaseball teams. 6. P1EitherDescarteswasFrenchor Socrates wasGreek. P2 SocrateswasnotGreek. C DescarteswasFrench. ANSWERS TOLOGICEXERCISES: A. UNDERSTANDINGDEDUCTIVEARGUMENTS All aretrueexceptnumber5. B. EVALUATINGDEDUCTIVEARGUMENTS 1. P1&Caretrue.Valid.Sound. 2. P1,P2&Caretrue.Valid.Sound. 3. P1isfalse(e.g.scrubbingtoilets maybe offensive,butit'snotimmoral).P2istrue,Cisfalse(though controversial). Valid(becauseIFthepremisesWEREtrue,theconclusionwouldhaveto betrue-thisisanexampleofthevalidargumentformaffirmingthe antecedent). Unsound,becauseP1isfalse. 4. P1&Caretrue.Invalid(The factthat someAlbanianshailfromAlbaniadoesnotmakeittruethatwealthy ones do.EvenifsomeAlbanianshailedfromAlbania,itcouldhavebeenthe casethatallthewealthyoneshailedfromsomeothercountry). Unsound, becausetheargumentisinvalid. 5. P1,P2&Caretrue.Invalid(The premises saynothingaboutwhethertheRedsortheCardinalsarebaseballteams, soitcouldhavebeenthecasethatbothpremisesweretrueyetthe Reds andtheIndiansweresoccerteams).Unsound,becausetheargumentis invalid. 6. P1&Caretrue,P2isfalse. Valid(because IFthepremisesWEREtrue,theconclusionwouldhavetobetrue). Unsound (becauseP2isfalse).