FALLACIES CHAPTERS 8 & 9. DEDUCTIVE REASONING From general to specific; have a law, premise, or...
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Transcript of FALLACIES CHAPTERS 8 & 9. DEDUCTIVE REASONING From general to specific; have a law, premise, or...
FALLACIESCHAPTERS 8 & 9
DEDUCTIVE REASONING
• From general to specific; have a law, premise, or principle
• Insert a specific fact or event regarding that law
• Come to a conclusion about that specific fact or event
• Stated in the form of SYLLOGISM
FORMAT OF SYLLOGISM
• Major premise = statement of law or principle• Minor premise = application of law to specific facts• Conclusion = derived from premises
DEDUCTIVE SYLLOGISMS
• DENYING THE CONSEQUENT
• AFFIRMING THE ANTECEDENT
• DISJUNCTIVE SYLLOGISM
• APPLYING A GENERALIZATION
• APPLYING AN EXCEPTION
• TRANSITIVITY RELATIONSHIP (HYOTHETICAL SYLLOGISM)
• REFLEXIVITY RELATIONSHIP
• IDENTITY RELATIONSHIP
DENYING THE CONSEQUENT
• Major Premise: If A then B
• Minor Premise: Not B
• Conclusion: Therefore, not A
• If Richard graduate with honors, then Richard maintained a GPA of 3.2 or higher.
• Richard did not maintain a GPA of 3.2 or higher
• Richard did not graduate with honors
AFFIRMING THE ANTECEDENT• Major Premise: If A then B
• Minor Premise: A
• Conclusion: Therefore, B
• If you are eligible to graduate with honors, you will get a Registrar’s notification
• You are eligible to graduate with honors
• So you will get a Registrar’s notification
• If the sun shines on the far side of the moon, then carrier pigeons are raised in Denver
• The sun shines on the far side of the moon
• Therefore, carrier pigeons are raised in Denver.
DISJUNCTIVE SYLLOGISM
• Either A or B• Not A• Therefore, B
• Either Romney won the presidency in 2012 or Obama did.• Romney didn’t win.• Therefore, Obama did win.
APPLYING A GENERALIZATION
• Major Premise: Every member of F is a member of G.
• Minor Premise: Individual object X is a member of F.
• Conclusion: So, X is a member of G.
• Every student in this class is a Medical Assisting Major.
• Janelly is in this class.
• So Janelly is a Medical Assisting major.
APPLYING AN EXCEPTION
• Major Premise: Every F is a G.
• Minor Premise: The object X is not a G.
• Conclusion: So X is not an F.
• Attic insulation installers run the risk of lung disease.
• Angela and Jennifer do not run the risk of lung disease.
• So Angela and Jennifer do not install attic insulation.
TRANSITIVITY RELATIONSHIP (HYPOTHETICAL SYLLOGISM)
• If A then B
• If B then C
• If A then C
• If I do not wake up, then I cannot go to work.
• If I cannot go to work, then I will not get paid.
• Therefore, if I do not wake up, then I will not get paid.
• Tom is taller than John.
• John is taller than Mark.
• So Tom is taller than Mark.
• All men are mortal
• Socrates is a man
• Therefore Socrates is mortal.
REFLEXIVITY RELATIONSHIP
• If X has a reflexive relationship to Y
• Then Y has the same reflexive relationship to X.
• Meryl Streep played Julia Child in the film Julie and Julia
• The actress who played Julia child in that film was nominated for an Oscar.
• Therefore Meryl Streep received an Oscar nomination for her performance in that film.
IDENTITY RELATIONSHIPS
• If X has a reflexive relationship to Y• Then Y has the same reflexive relationship to X.
• If all bachelors are unmarried males, then all unmarried males are bachelors.
DEDUCTIVE FALLACIES
• Affirming the Consequent• Denying the Antecedent• False Classification• Composition• Division• False Reference
AFFIRMING THE CONSEQUENT (THE HOUSE M.D. FALLACY)• Major Premise: If A then B
• Minor Premise: B
• Conclusion: Therefore, A
• If we put a human on Mars, then we have a successful space program.
• We have a successful space program.
• Therefore we have put a human on Mars.
• All dogs eat meat.
• Bob (a human) eats meat.
• Therefore, Bob is dog.
DENYING THE ANTECEDENT
• Major Premise: If A then B
• Minor Premise: Not A
• Conclusion: Therefore, not B
• If we see a light in the window then someone is home.
• No light is in the window.
• Therefore, no one is home.
• If all college students drank red wine the wine industry would be booming.
• The wine industry is booming.
• Therefore, all college students drink red wine
FALSE CLASSIFICATION FALLACY
• Major Premise: A has quality X
• Minor Premise: B has quality X
• Conclusion: Therefore, A is B.
• Criminals enjoy mafia movies
• Cassandra enjoys mafia movies.
• Therefore, Cassandra is a criminal.
• See P. 159 for more examples
COMPOSITION AND DIVISION FALLACIES
• Mistaking a whole for the part: Attributing characteristics to the whole which are true for the part.
• Mistaking a whole for the part: Attributing characteristics to the whole which are true for the part.
• See page 160.
FALSE REFERENCE FALLACY
• My Cousin Vinny: Vinny gets arrested for confessing to murder when he thought he was confessing to shoplifting a can of tuna fish.
• “I lost hope.”
• I hear that the Tour de France winter used banned performance enhancing drugs. I also heard that Cadel Evans won the 2011 Tour de France. Therefore, Evans used banned performance enhancing drugs.
EVALUATING ARGUMENTS
• Page 163