Introduction to Logic

1. Second Grading Period, S.Y. 2013-2014 Introduction to Logic

2. Topics • Inductive Reasoning • Informal Fallacies • Fallacies of Relevance • Fallacies of Defective Induction • Fallacies of Presumption • Fallacies of Ambiguity

3. Task • Fallacies in Media (December 2 to 6, 2013)

4. Copy the notes on Fallacies of Relevance and Fallacies of Defective Induction. • For next week: • Prepare for a quiz on 1st Grading Period concepts and terms (premise and conclusion, incomplete arguments, and deductive argument forms) • Bring the summaries and discussion of the significance of your three articles. Be ready to write your letter to the editor.

5. INFORMAL FALLACIES Plato “Arguments, like men, are often pretenders.”

6. Informal Fallacies • Patterns of mistake that are made in the everyday uses of language • Errors in reasoning that arise from the content of the argument, not its form

7. Classes of Informal Fallacies • Fallacies of Relevance • Fallacies of Defective Induction • Fallacies of Presumption • Fallacies of Ambiguity

8. Fallacies of Relevance The conclusion is logically irrelevant to the premises, even if it is psychologically or emotionally relevant.

9. Appeal to Emotion (Ad Populum) • Reliance is made on expressive language and other devices to excite the emotions for or against some cause [1]

10. Argument Against the Person(Ad Hominem) • The attack is directed not at the argument but at the person who defends it [2]

11. Argument Against the Person(Ad Hominem) • May be abusive (mocking the character of one’s opponent) or circumstantial (calling attention to the special circumstances of one’s opponent) [2]

12. Appeal to Force (Ad Baculum) • Threats or strong-arm methods are used to persuade others to accept an argument • May involve physical or psychological harm, and may be direct or veiled [3]

13. The Red Herring • A distraction or deliberately misleading trail • Attention is drawn to some other aspect of the topic and led away from the issue [4]

14. The Straw Man • The position of one’s opponent is misrepresented, distorted, exaggerated or oversimplified [5]

15. Fallacies of Defective Induction The premises are inadequate or insufficient to reach the conclusion drawn.

16. Appeal to Ignorance (Ad ignorantiam) • When it is argued that a proposition is true because it has not been proved false (or it is false because it has not been proved true) [1]

17. Appeal to Inappropriate Authority (Ad Verecundiam) • When the argument appeals to the judgment of a person who has no legitimate claim to authority in the matter at hand [2]

18. False Cause • When one treats as the cause of a thing something which is not really its cause • Often relies merely on fact that the two events happen one after another [3]

19. Hasty Generalization (Converse Accident) • When one moves carelessly or too quickly from one or a very few instances to a broad or universal claim [4]