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Informal Fallacies

Informal Fallacies. Chapter 5. Formal vs. Informal fallacy. Formal The logic is wrong– Not sound Bad reason fallacy : error in the way the argument is structured or built (invalid set up, 9 rules ) Doesn't force a true conclusion with all true premise Informal

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Informal Fallacies

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  1. Informal Fallacies Chapter 5

  2. Formal vs. Informal fallacy • Formal • The logic is wrong– Not sound • Bad reason fallacy: error in the way the argument is structured or built (invalid set up, 9 rules) • Doesn't force a true conclusion with all true premise • Informal • Mask Man fallacy: subjective, emotional language in propositions. The masked man is Mr. Hyde. TThe witness believes the masked man committed the crime. TTherefore, Mr. Hyde committed the crime. F

  3. Informal Fallacy • Error with the content of arguments • Words chosen • Phrases chosen • How we express our arguments • Can be formally valid, built logically • Allows you to notice irrational thought Informal fallacies are defects found in the content of the argument, which could be inductive or deductive.

  4. Major types of informal fallacies • Fallacies of ambiguity (Cleaner) • The words or phrases need to be defined- or are vague- or change meaning in the argument • Fallacies of relevance (Connection) • The considerations that are offered in support of the conclusion are irrelevant to determining whether that conclusion is true. It makes it possible for the premises to all be true and conclusion to be false. • Fallacies of assumption (Conjecture) • Have false (or at least unwarranted) assumptions, which fails to establish inference to the conclusion (must be true). Assume one premise to be true

  5. Fallacies of ambiguity Word choices makes a confusing premise

  6. Equivocation • Words often have more than one meaning • Different definition of word or phrase • Use subjective or relative words or phrases • Tall/Short • Hot/Cold • What are rights? • What’s a good salary? • What’s a good mate? • “I’m to see the Doctor…………………”

  7. Amphiboly • Grammatical error leads to confusion. • Bad or unclear writing/speaking • A man shot himself after making a fond farewell to his family with a shotgun • Is it the man shot himself with a shot gun or that he gave his family a fond farewell with a shotgun • Ad for an apartment: 3 rooms, river view, private phone, bath, kitchen, utilities included • Is it just a private phone or private phone, bath and kitchen?

  8. Accent • Different emphasis on certain words changes meaning or context • THESE (!) are your friends • These are YOUR(!) friends You misinterpret the meaning because of and accent on a word or phrase • Can be cultural or regional • Automobile story

  9. Composition • The whole is like the individual • Buses use more gas then cars • True one bus to one car BUT NOT ALL buses to ALL cars (more cars) • Can be fixed by clarifying wording Most buses uses more gas than automobiles, but there are more automobiles. Thus, as a whole- automobiles use more gas

  10. Division • The pieces are like the whole • This hotel must have nice suites because the outside and lobby is so nice. • The whole car is of quality means every part in the car is of quality • ALL men are DOGS. Mr. V is a man, therefore Mr. V is a DOG!

  11. Name that Fallacy

  12. Fallacies of relevance Premises are unrelated to conclusion

  13. Emotion • Rely on the feelings of the audience to influence one’s argument • Patriotic speeches (Hitler) • Ads on TV (Shoes-- Athlete) • Appeal to pity (Court Cases) • I was late for work that is why I was speeding

  14. Red Herring- distraction • Distract the other person from real argument or too ambiguous of a connection. • Loose(n) focus. • Gambling is good because taxes are too high • We need to be in Iraq, only 800 Iraqi soldiers (T/F?) • Duke (2006): Three students accused of rape, one professor defended the prosecutor’s indictment by saying that the real bad thing is that 18% of the population was below the poverty line.

  15. Straw Man • Change opponents argument. Putting words in opponents mouth to make it easier to refute or beat • When you talk about universal health care you are talking about Socialism. • When you are talking about same sex marriage you are saying we need to destroy the family dynamics in the US.

  16. Against the personLatin: ad hominem • You don’t attack argument you attack the person who is arguing with you • Abusive: Direct attack on the person • If against affirmed action, then you are a racist • If you are a liberal, then you are part of the “Loony Left” • Circumstantial: Attack a person’s status/group. Also called Poisoning the well • If you go to that school, then you are not smart • If those are your friends then you are bad too

  17. Appeal to force • To force someone to accept a claim with a physical or physiological confrontation • Physical force • Lawsuits to scare • Symbols to influence • Nazi • American Flag • Police shield

  18. From Ignorance • Assume true because not proven false OR • Assume false because not proven true • You have to make your own argument • You can’t prove UFOs are false so they must be true • You can’t prove I’m guilty so I must be Innocent.

  19. Name that Fallacy

  20. Fallacies of Assumptions Assume premise to be true without proof

  21. Begging the question • The conclusion is just a rewording of one of the premises. Also called circular logic • Freedom of speech is good because everyone is free to say what they want. • Capital punishment is wrong because you are putting someone to death is wrong. • God exists because the bible says so (which is the word of God)

  22. Inappropriate Authority • Use testimony of expert (credibility) in an area that they are not an expert in. • Politics • The president thinks genetic engineer is wrong/right • Is he/she a scientists? • Ads • Tiger Woods Drives this car • Does he race or engineer cars?

  23. Loaded (Complex) Question • Suppose the truth of another question in a premise to justify the conclusion • How did you feel when you took all that money from the bank? • Assumes you did take it and the question asks about your emotions • You support the right to bear arms and the Republican Party. • Assumes you support both causes

  24. False Dilemma • Forces the argument into two choices when there are many. Limits your options. • Very popular in Politics, sports and relationships • Either you are with us or against us • Either you like the team or hate the team • Either you love me or you don’t

  25. False Cause • The casual relationship in a premise is not a true relationship. • Less religion in school causes gangs • Death penalty decreases crime Could be plenty of other factors that cause gangs and decreases crime. Could be one factor, but maybe not the most important one

  26. Name that Fallacy

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