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LOGICAL REASONING Study Unit 5 – eLearning RPK 214

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Cannot engage in logical reasoning? o Poor legal arguments o Loss of cases And if you cannot win cases... You MUST learn logical reasoning… Base arguments on emotion / feeling?

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Convine your audience of your case, including your interpretation of the law Solve legal problems Test the acceptability of conclusions Initial assumption (premise) Interim conclusions (inferences) Final conclusion Rules of logic

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PREMISE / STARTING ASSUMPTION MUST BE TRUE / ACCEPTABLE VALID INFERENCE / INTERIM CONCLUSION MUST BE VALID FINAL CONCLUSION MUST FOLLOW LOGICALLY FROM THE ABOVE If NOT follow logically: INVALID reasoning / non sequitur If DOES follow: argument SOUND!

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PREMISE / STARTING ASSUMPTION MUST BE TRUE / ACCEPTABLE All men are liars Thapelo is a man VALID INFERENCE / INTERIM CONCLUSION MUST BE VALID Thapelo is a liar FINAL CONCLUSION MUST FOLLOW LOGICALLY FROM THE ABOVE Premises = Untrue / unacceptable BUT: Conclusion = Valid – follows logically from premises Argument is unsound

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PREMISE / STARTING ASSUMPTION MUST BE TRUE / ACCEPTABLE 1: Fingerprints were found on the gun 2: The fingerprints belong to Jimmy VALID INFERENCE / INTERIM CONCLUSION MUST BE VALID Jimmys finger touched the gun FINAL CONCLUSION MUST FOLLOW LOGICALLY FROM THE ABOVE Premises = True / acceptable Conclusion = Valid – follows logically from premises Argument is sound

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PREMISE / STARTING ASSUMPTION MUST BE TRUE / ACCEPTABLE 1: Fingerprints were found on the gun 2: The fingerprints belong to Jimmy VALID INFERENCE / INTERIM CONCLUSION MUST BE VALID Jimmy shot the victim FINAL CONCLUSION MUST FOLLOW LOGICALLY FROM THE ABOVE ?

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PREMISE / STARTING ASSUMPTION MUST BE TRUE / ACCEPTABLE 1: Fingerprints were found on the gun 2: The fingerprints belong to Jimmy VALID INFERENCE / INTERIM CONCLUSION MUST BE VALID Jimmy may have shot the victim FINAL CONCLUSION MUST FOLLOW LOGICALLY FROM THE ABOVE Premises = True / acceptable Conclusion = Valid – follows logically from premises Argument is sound

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CONCLUSIVE INFERENCE Jimmy touched the weapon vs PROBABILITY INFERENCE Jimmy shot the victim DEDUCTIVE REASONING INDUCTIVE REASONING

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CONCLUSIVE INFERENCES Premise = TRUE Inference = ALSO TRUE Argument = VALID (an argument is valid if conclusions follows premises) PROBABLE INFERENCES The higher the PROBABILITY, the more persuasive the argument Syllogism

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PREMISE 1:JOHN COMMITTED FRAUD PREMISE 2:PEOPLE WHO COMMIT FRAUD ARE INTELLIGENT CONCLUSION:JOHN IS INTELLIGENT PROCESS OF REASONING / INFERENCE PREMISEREASONING CONCLUSION

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IF... PREMISES = True / acceptable PROCESS OF REASONING = Valid Final conclusions MUST BE ACCEPTED Argument is 100% concusive

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BUT... Practice of law... Premises & inferences cannot always be proven to be 100% conclusive

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Argument made using inductive reasoning Prove argument by relying on different starting premises to prove argument = PROBABLY true Proven on balance of probabilities < persuasive than deductive reasoning > persuasive than nothing! degree of probability, persuasive effect

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PREMISE 1:A group of 30 armed men is gathered outside the courtroom PREMISE 2:Many members of the group are threatening to kill Bill Conclusion:It is, therefore, PROBABLE that Bills life will be in danger if he is released on bail

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PREMISE False / unacceptable PROCESS OF REASONING / inferences drawn…flawed (Logical fallacy – causative / preconceptions / Tautologous) Final conclusion does not follow series of inferences (non sequitur)

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If you argue deductively & your opponent refuses to accept your premises... Switch to inductive reasoning... If fail: opponent must prove his assertions

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When is premises true / accepted? EVIDENCE! Logical fallacies – When the evidence fails us Causal fallacy Preconceived ideas Appealing to authority Tautologous arguments

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Not understanding the correct meaning of words / concepts fuzzy thinking & fuzzy writing Using words without understanding meaning properly opportunity for the opposition to attack reasoning on premise Understanding words & concepts will allow YOU to attack oppositions premises

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Remember to complete class exercise 8…

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