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