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Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
Week 3
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Week 3

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Week 3

Week 3

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  • 1. LOGICProf Roy Shaff
    Week 3
    1
  • 2. Key Terms for Ch 4
  • 3. Objectives
    3
    When you complete this lesson, you will be able to recognize:
    Fallacies of relevance
    Fallacies of defective induction
    Fallacies of presumption
    Fallacies of ambiguity
  • 4. What is a Fallacy?
    4
    A type of argument that may seem to be correct but contains a mistake in reasoning
    Known to be deceptive
    YouTube - Monty Python - Argument Clinic
  • 5. The Classifications of Fallacies
    5
    Fallacies of relevance
    Premises are simply not relevant to the conclusion drawn
    Fallacies of defective induction
    Premises of the argument are so weak and ineffective that reliance upon them is wrong
    Fallacies of presumption
    Too much has been assumed in the premises
    Fallacies of ambiguity
    Use of words or phrases where a critical term has different senses in different parts of the argument
  • 6. Fallacies of Relevance
    6
    Appeal to emotion
    Relies on expressive language and other devices calculated to excite enthusiasm for or against some cause in place of evidence and rational argument
    YouTube - Advertising Fallacies
  • 7. Fallacies of Relevance, continued
    7
    Appeal to pity
    Argument relies on generosity, altruism, or mercy, rather than reason
    http://www.youtube.com/watch?v=7-YpcrJEe78
  • 8. Fallacies of Relevance, continued
    8
    Appeal to force
    Argument relies on the threat of force
    The threat may be veiled
  • 9. Fallacies of Relevance, continued
    9
    Argument against the person (argument ad hominem)
    Argument relies on character assassination of the individual taking the opposing position
    Abusive
    Denies opponent’s intelligence, reasonableness, seriousness, or integrity
    Circumstantial
    Opponent is obliged to accept or reject some conclusion merely because of employment, nationality, political affiliation, or other circumstances
  • 10. Fallacies of Relevance, continued
    10
    Irrelevant conclusion
    The premises go in one direction, and the conclusion goes in another direction
    Straw man
    The opponent’s position is misrepresented
    YouTube - The "Straw Man" Fallacy
    Red herring
    A distracting element is introduced to obscure an opponent’s position
    YouTube - The "Red Herring" Fallacy
    Non sequitor (“does not follow”)is a term often applied to irrelevant conclusions
  • 11. Fallacies of Defective Induction
    11
    Argument from ignorance (argument ad ignorantiam)
    Proposition is held to be true just because it is not been proved false, or false just because it has not been proved true
  • 12. Fallacies of Defective Induction, continued
    12
    Appeal to inappropriate authority
    Conclusion is based on the judgment of a supposed authority who has no legitimate claim to expertise in the matter
  • 13. Fallacies of Defective Induction, continued
    13
    False cause
    Something that is not really a cause is treated like a cause
    Fallacy of post hoc ergo propter hoc
    “After the thing, therefore because of the thing”
    Slippery slope
    Any change in a particular direction is sure to lead to further changes in the same direction, and on to grave consequences
    http://www.youtube.com/watch?v=DtmAw9Ia7LA
  • 14. Fallacies of Defective Induction, continued
    14
    Hasty generalization (converse accident)
    Moving carelessly from individual cases to generalization
    A leap is made to a broad generalization on the basis of very little evidence
  • 15. Fallacies of Presumption
    15
    Accident
    Opposite of hasty generalization
    Moving carelessly or unjustifiably from a generalization to some particulars that it does not cover in fact
  • 16. Fallacies of Presumption, continued
    16
    Complex question
    A question is asked in a way that presupposes the truth of some proposition buried within the question
  • 17. Fallacies of Presumption, continued
    17
    Begging the question (petitioprincipii)
    Conclusion is stated or assumed within one of the premises
    Circular argument
    http://www.youtube.com/watch?v=YoOd7QfRW5s
  • 18. Fallacies of Ambiguity
    18
    Equivocation
    Two or more meanings of a word or phrase are used in different parts of an argument
    Use of relative terms
    http://www.youtube.com/watch?v=sShMA85pv8M
  • 19. Fallacies of Ambiguity, continued
    19
    Amphiboly
    Loose or awkward combination of words can be interpreted more than one way
    Argument contains a premise based on one interpretation while the conclusion relies on a different interpretation
  • 20. Fallacies of Ambiguity, continued
    20
    Accent
    Phrase is used to convey two different meanings within an argument, and the difference is based on changes in emphasis given to the words within the phrase
  • 21. Fallacies of Ambiguity, continued
    21
    Composition
    Inference is drawn mistakenly from the attributes of the parts to the attributes of the whole
    Reasoning fallaciously from the attributes of the parts of a whole to the attributes of the whole itself
    Reasoning from attributes of the individual elements or members of a collection to attributes of the collection or totality of those elements
  • 22. Fallacies of Ambiguity, continued
    22
    Division
    Inference is drawn from the attributes of a whole to the attributes of the parts
    Arguing fallaciously that what is true of a whole must be true of its parts
    Arguing from the attributes of a collection of elements to the attributes of the elements themselves
  • 23. Case Study
    23
    YouTube - CAS 100B - 12 Angry Men clips
  • 24. Summary
    24
    Fallacies of relevance
    Fallacies of defective induction
    Fallacies of presumption
    Fallacies of ambiguity

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