Week 3

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Week 3

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Week 3

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

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