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Fallacies. Flaws in the Structure of an Argument. What are fallacies?. Fallacies are defects in an argument. Fallacies cause an argument to be invalid, unsound, or weak. Fallacies can be separated into two general groups: formal and informal . . Formal Fallacies.

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  1. Fallacies Flaws in the Structure of an Argument

  2. What are fallacies? • Fallacies are defects in an argument. • Fallacies cause an argument to be invalid, unsound, or weak. • Fallacies can be separated into two general groups: formal and informal.

  3. Formal Fallacies • Formal fallacies are only found in deductive arguments. • Deductive arguments are supposed to be air-tight. • For a deductive argument to be valid, it must be absolutely impossible for both its premises to be true and its conclusion to be false. With a good deductive argument, that simply cannot happen; the truth of the premises entails the truth of the conclusion.

  4. Formal Fallacies • The classic example of a deductively valid argument is: • 1. All men are mortal. (premise) • 2. Socrates is a man. (premise) • 3. Therefore Socrates is mortal. (guaranteed conclusion) • It is simply not possible that both (1) and (2) are true and (3) is false, so this argument is deductively valid.

  5. Formal Fallacies • Any deductive argument that fails to meet this very highstandard commits a logical error, and so, technically, is fallacious. • This includes many arguments that we would usually accept as good arguments, arguments that make their conclusions highly probable but not certain. • Arguments that aren’t deductively valid are said to commit a “formal fallacy.”

  6. Formal Fallacies • Example of a deductive argument with a formal fallacy: 1. All humans are mammals. (premise)2. All cats are mammals. (premise)3. All humans are cats. (conclusion) • Both premises in this argument are true but the conclusion is false. The defect is a formal fallacy and can be demonstrated by reducing the argument to its bare structure: 1. All A are C2. All B are C3. All A are B

  7. Formal Fallacies • With deductive arguments, it can be helpful to reduce an argument to its structure. • All chickens are feathered animals. (premise) • Clucko is a chicken. (premise) • Therefore Clucko is a feathered animal. (guaranteed conclusion)

  8. Formal Fallacies • All chickens are feathered animals. (premise) • Quacko is a feathered animal. (premise) • Therefore Quacko is a chicken. (non-guaranteed conclusion) • This argument commits a formal fallacy in that its form doesn’t guarantee the truth of its conclusion, even if the initial premises are true.

  9. The Problem of Conclusiveness in an Argument • Real-world arguments address contestable issues of truth and value that cannot be resolved with mathematical certainty. • Disputants can create only more or less persuasive arguments, never conclusive ones.

  10. The Problem of Conclusiveness in an Argument

  11. Informal Fallacies • They are flaws in the structure of an argument. • They are embedded in many everyday arguments. • They sometimes make fallacious reasoning seem deceptively persuasive

  12. Why Study Informal Fallacies? • Knowledge of informal fallacies is most useful when we run across arguments that we “know” are wrong, but we cannot quite say why. • Knowledge of informal fallacies can help you locate specific weaknesses in others’ arguments . . . and in your own!

  13. Warning! • Most students who study fallacies begin to find them plentiful in the arguments of those with whom they disagree. • Realize that fallacies are most likely being used with equal frequency by you, as well as your friends. • Test your integrity by diligently seeking fallacies in your own arguments.

  14. Informal Fallacies: Three Categories • Fallacies of Pathos • Fallacies of Ethos • Fallacies of Logos

  15. Fallacies of Pathos • Rest on flaws in the way an argument appeals to the audience’s emotions and values • Argument to the People • Appeal to Ignorance • Appeal to Popularity • Appeal to Pity • Red Herring

  16. Argument to the PeopleAppeal to Stirring Symbols • Appeal to the fundamental beliefs, biases, and prejudices of the audience in order to sway opinion through a feeling of solidarity among those of a group.

  17. Argument to the PeopleAppeal to Stirring Symbols • The stirring symbol of the American flag • Allegiance to nationalistic values • Solidarity of American citizens • Ex: Joe Politician delivering a speech while wearing a suit made out material patterned with the American flag. • Ex: Marilyn Manson wiping his butt on an American flag.

  18. Appeal to Ignorance • Presenting assumptions, assertions, or evidence that the audience is incapable of examining or judging. • Maintaining that because a claim has not been disproved, it must be true.

  19. Appeal to Ignorance • Ex: Researchers have not conclusively shown that there is no monster at the bottom of Loch Ness; therefore, we should expect to see the monster at any time. • Ex: There must be intelligent life on other planets. No one has proven that there isn’t.

  20. Appeal to Ignorance • Ex: Genetically modified organisms must be dangerous to our health because science has not proved that they are safe. • Ex: Jones must have used steroids to get those bulging muscles because he cannot prove that he has not used steroids.

  21. Appeal to PopularityThe Bandwagon Appeal • The argument rests on the assertion that since everybody else is doing something, you should do it too. • These appeals are fallacious because the popularity of something is irrelevant to its actual merits. • These appeals are common in advertising where the claim that a product is popular substitutes for evidence of the product’s excellence.

  22. Appeal to PopularityThe Bandwagon Appeal • Ex: All the popular, cool kids have tattoos; therefore, I should get a tattoo. • Ex: Everybody who has a Facebook page has a lot of friends; therefore, I should make a Facebook page.

  23. Appeal to PopularityThe Bandwagon Appeal • Ex: Living together before marriage is the right thing to do because most couples are now doing it. • Ex: You should buy a Toyota Camry because itis the best-selling car in the world.

  24. Appeal to Pity • The arguer appeals to the audience’s sympathetic feelings in order to support a claim that should be decided on more relevant or objective grounds.

  25. Appeal to Pity • Ex: “Professor Rose, I’m sorry I couldn’t finish my essay. You don’t understand how difficult my life is right now. My parents could not afford to send me to college, and I have to work two part-time jobs to pay for my classes and books.”

  26. Appeal to Pity • Ex: “Honorable Judge, I should not be fined $250 for driving 85 mph in a 25 mph zone because I was distraught from hearing the news of my brother’s illness and was rushing to see him in the hospital.”

  27. Red Herring • Refers to the practice of throwing an audience off track by raising an unrelated or irrelevant point. • The name derives from the practice of using a red herring (a very smelly fish) to throw dogs off from a scent that they are supposed to be tracking.

  28. Red Herring • Ex: Jack’s girlfriend asks, “Where were you last night?” Jack answers, “I sure am glad to see you. You look extra beautiful today!” • Ex: Question to politician, “What’s your stand on gun control?” Politician’s reply, “I’m for family values.”

  29. Red Herring • Ex: I don’t believe we should elect this candidate because she would have to put her children in daycare.

  30. Fallacies of Ethos • Fallacies of Ethos = Rest on a flawed relationship between the argument and the character of those involved in the argument. • Often these fallacies attack character or use character instead of evidence for proof.

  31. Appeal to False Authority • The arguer appeals to the authority of a popular person rather than a knowledgeable one. • Many advertisements are based on this fallacy. • Testimony to support an argument should come from a person competent in the field.

  32. Appeal to False Authority • Kobe Bryant says that Wheaties cereal keeps him on his game; therefore, Wheaties cereal is a good cereal. • Real evidence about the quality of Wheaties cereal would include specific information about its nutritional content rather than testimony from a hired athlete.

  33. Appeal to False Authority • My favorite actor, who appeared in a movie about AIDS, has testified that the HIV virus doesn’t really cause AIDS and that there has been a cover-up. So, I think that AIDS must be caused by something other than HIV, and the drug companies are hiding it so that they can make money from expensive anti-HIV drugs. • The above argument bases its conclusion on the testimony of an actor, apparently because he appeared in a movie on the topic. Legitimate testimony on the nature of AIDS would have to come from doctors or scientists.

  34. Appeal to False Authority • Tom Cruise says that postpartum depression can be best treated with vitamins because anti-depressant drugs are dangerous. Therefore, all women who claim they have postpartum depression should stop taking anti-depressants and start taking vitamins.

  35. Ad HominemAppeal to the person • Arguments that attack the character of the arguer rather than the argument itself • Name-calling (referring to a disputant by unsavory names) • Appeal to prejudice (applying ethnic, racial, gender, or religious slurs to an opponent) • Guilt by association (linking the opposition to extremely unpopular groups or causes) • Poisoning the Well (discrediting an opponent or an opposing view in advance)

  36. Ad HominemAppeal to the person • Name-calling • Ex: OJ Simpson claims that he is innocent, but he’s a wife beater. • Ex: Hugh Hefner, founder of Playboy magazine, has argued against the censorship of pornography. But Hefner is an immature, self-indulgent millionaire who never outgrew the adolescent fantasies of his youth. His argument is worthless. • Ex: All wars are not wrong. The people who say so are cowards.

  37. Ad HominemAppeal to the person • Appeal to prejudice • Ex: Because he is extremely wealthy, our mayor cannot properly represent this city. • Ex: I reject what Father Rolly has to say about the ethical issues of abortion because he is a Catholic priest. After all, Father Rolly is required to hold such views. • Ex: Of course she is in favor of Affirmative Action. What do you expect from a black woman?

  38. Ad HominemAppeal to the person • Guilt by Association • Ex: Of course you support medical marijuana. All of your friends are a bunch of pot-head hippies. • Ex: Professor Smith has argued against the theory of evolution. But he’s a member of the Communist Bikers’ Association. I refuse to listen to him!

  39. Ad HominemAppeal to the person • Poisoning the Well • Ex: You are told, prior to meeting him, that your friend’s boyfriend is a poseur and a mooch. When you meet him, everything you hear him say is tainted. • Ex: Before I leave the floor to the next speaker, I must remind you that persons who oppose my plan do not have the best interests of the working people in their hearts.

  40. Straw Man • Greatly oversimplifying an opponent’s argument in order to make it easier to refute or ridicule • Diverts attention from the real issue • The name comes from the practice of stuffing dummies and scarecrows with straw. When one attacks an opponent by putting words into the opponent’s mouth, one makes up a “dummy” position. But just as beating up a scarecrow doesn’t demonstrate any athletic accomplishment, beating up a “straw man” in an argument doesn’t demonstrate anything.

  41. Straw Man • Ex: You many think that levying confiscatory taxes on homeless people’s cardboard dwellings is the surest way out of a recession, but I don’t. • Ex: While my opponent would like to empty our prisons of serial killers, I hold to the sacred principles of compensatory justice.

  42. Fallacies of Logos • Rest on flaws in the relationship among statements in an argument

  43. Hasty Generalization • Making a broad generalization on the basis of too little evidence • Traditionally, faulty generalizations have been labeled either “hasty” or “unrepresentative.”

  44. Hasty Generalization • Ex: Yesterday I met the most remarkable person. He is kind, considerate, sensitive, and thoughtful. • Ex: I talked to five people in my neighborhood, and all of them said they had guns. The whole city must be armed.

  45. Hasty Generalization • Ex: My cousin is a college student, and he doesn’t care the least bit about politics. Students these days are terribly apathetic. • Ex: Jean writes poetry, and she’s very sensitive and frequently depressed. People who write poetry are sensitive and prone to depression.

  46. Post Hoc, Ergo Propter HocAfter This, Therefore Because of This • Occurs when a sequential relationship is mistaken for a causal relationship • Confusing correlation for cause • Ex: Event A occurred before Event B; therefore, Event A must have caused Event B.

  47. Post Hoc, Ergo Propter HocAfter This, Therefore Because of This • Ex: Governor X took office in 2008. In 2009, the state suffered a severe recession. Therefore, Governor X should not be re-elected. • Ex: Cramming for a test really helps. Last week I crammed for a psychology test, and I got an A on it.

  48. Post Hoc, Ergo Propter HocAfter This, Therefore Because of This • Superstition is often based on this fallacy. • Ex: Since I walked under that ladder yesterday, I’ve lost my wallet and received a speeding ticket. • Ex: Everything was going fine until the lunar eclipse last month; that’s why the economy is in trouble.

  49. Begging the QuestionCircular Reasoning • Supporting a claim with a reason that simply restates the claim in different words • Ex: Bungee-jumping is dangerous because it’s unsafe. • Ex: Women should not be permitted to join men’s clubs because the clubs are for men only.

  50. Begging the QuestionCircular Reasoning • Ex: Abortion is murder because it is the intentional taking of the life of a human being. • Because “murder” is defined as the “intentional taking of the life of a human being,” the argument is circular.

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