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

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Fallacies

Fallacies

Flaws in the Structure of an Argument


What are fallacies

What are fallacies?

  • Fallacies are defects in an argument that cause it to be invalid, unsound, or weak.

  • Fallacies can be separated into two general groups: formal and informal.


Formal fallacies

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.


Formal fallacies1

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.


Formal fallacies2

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.”


Formal fallacies3

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


Formal fallacies4

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)


Formal fallacies5

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.


  • The problem of conclusiveness in an argument

    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.


    The problem of conclusiveness in an argument1

    The Problem of Conclusiveness in an Argument


    Informal fallacies

    Informal Fallacies

    • They are flaws in the structure of an argument.

    • They sometimes make flawed reasoning seem deceptively persuasive.


    Why study informal fallacies

    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!


    Informal fallacies three categories

    Informal Fallacies: Three Categories

    • Fallacies of Pathos

    • Fallacies of Ethos

    • Fallacies of Logos


    Fallacies of pathos

    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


    Argument to the people appeal to stirring symbols

    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.


    Argument to the people appeal to stirring symbols1

    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.


    Appeal to ignorance

    Appeal to Ignorance

    • Presenting assumptions, assertions, or evidence that the audience is incapable of examining or judging.

    • In other words, maintaining that because a claim has not been disproved, it must be true.


    Appeal to ignorance1

    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.


    Appeal to ignorance2

    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.


    Appeal to popularity the bandwagon appeal

    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.


    Appeal to popularity the bandwagon appeal1

    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.


    Appeal to popularity the bandwagon appeal2

    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.


    Appeal to pity

    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.


    Appeal to pity1

    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.”


    Appeal to pity2

    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.”


    Red herring

    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.


    Red herring1

    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.”


    Red herring2

    Red Herring

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


    Fallacies of ethos

    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.


    Appeal to false authority

    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.


    Appeal to false authority1

    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.


    Appeal to false authority2

    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.


    Ad hominem appeal to the person

    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)


    Ad hominem appeal to the person1

    Ad HominemAppeal to the person

    • In politics, Ad Hominem can be found on the first page--nay, the first few words--of every politician's playbook. Why debate the pros and cons of universal health care when you can just call your opponent a socialist and get a cheer from the conservatives in the audience?

    • There are lots of words that get thrown around in political ad hominem arguments, leading to the common charge of "name-calling" and "mud-slinging": racist, nazi, hippy, teabagger, anti-christ, etc.


    Ad hominem appeal to the person2

    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.


    Ad hominem appeal to the person3

    Ad HominemAppeal to the person

    • Appeal to prejudice

      • Ex: Because he is extremely wealthy, our mayor cannot properly represent this city.

      • Ex: Of course she is in favor of Affirmative Action. What do you expect from a black woman?


    Ad hominem appeal to the person4

    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!


    Ad hominem appeal to the person5

    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.


    Straw man

    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.


    Straw man1

    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.


    Fallacies of logos

    Fallacies of Logos

    • Rest on flaws in the relationship among statements in an argument


    Hasty generalization

    Hasty Generalization

    • Making a broad generalization on the basis of too little evidence

    • Ex: Yesterday I met the most remarkable person. He is kind, considerate, sensitive, and thoughtful.


    Hasty generalization1

    Hasty Generalization

    • Ex: Jean writes poetry, and she’s very sensitive and frequently depressed. People who write poetry are sensitive and prone to depression.


    Post hoc ergo propter hoc after this therefore because of this

    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.


    Post hoc ergo propter hoc after this therefore because of this1

    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.


    Post hoc ergo propter hoc after this therefore because of this2

    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.


    Begging the question circular reasoning

    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.


    Begging the question circular reasoning1

    Begging the QuestionCircular Reasoning

    • Ex: Abortion is murder because it is the intentional taking of the life of a human being.


    False dilemma either or

    False Dilemma – Either/Or

    • Oversimplifying a complex issue so that only two choices appear possible

    • No alternative, middle-ground, or compromise positions are acknowledged.

    • Often one of the choices is made to seem unacceptable , so the only remaining option is the other choice.

      • Ex: It’s my way or the highway.


    False dilemma either or1

    False Dilemma – Either/Or

    • Ex: Love football or you’re not a man.

    • Ex: A woman can either be a mother or have a career.

    • Ex: Either we get tough with drug users, or we legalize all drugs.


    False dilemma either or2

    False Dilemma – Either/Or


    Slippery slope

    Slippery Slope

    • Based on the fear that once we put a foot on a slippery slope heading in the wrong direction, we will have to keep going.

    • Often functions as a scare tactic


    Slippery slope1

    Slippery Slope

    • Ex: Look, Joe, no one feels worse about your need for open-heart surgery than I do. But I still cannot let you turn this essay in late. If I were to let you do it, then Iwould have to let everyone turn essays in late.


    Slippery slope2

    Slippery Slope

    • Ex: We don’t dare legalize marijuana. If we do, we’ll have to legalize cocaine, then ecstasy, and then heroin. Finally, all hard hard drugs will be available anywhere to anybody.


    False analogy

    False Analogy

    • Arguments by analogy use a comparison as though it were evidence to support a claim.

    • An argument by analogy is only as strong as the comparison on which it rests. The false analogy fallacy is committed when the comparison is not strong enough.


    False analogy1

    False Analogy

    • Ex: There is no convincing evidence to show that cigarette smoking is harmful. Too much of anything is harmful. Too much Jell-O is harmful.


    False analogy2

    False Analogy

    • Ex: Mountain climber talking to his mother, “I don’t want to die falling off a rock. But you can kill yourself falling in the bathtub, too.”


    False analogy3

    False Analogy

    • Ex: In his autobiography, Tommy Chong writes that when DEA (Drug Enforcement Administration) agents raided his house he saw himself as “Anne Frank talking to Herr Mengele. . . For the first time, I felt like I could understand what the Jews suffered under Hitler, and this was happening in America in 2003.”


    False analogy4

    False Analogy


    Non sequitur it does not follow

    Non SequiturIt Does Not Follow

    • Making a claim that does not follow logically from the premises or is supported by irrelevant premises.

    • The arguer seems to make an inexplicably illogical leap.


    Non sequitur it does not follow1

    Non SequiturIt Does Not Follow

    • Ex: Violent video games have some social value because the Army uses them for recruiting.

    • There may be an important idea emerging here, but too many logical steps are missing.


    Non sequitur it does not follow2

    Non SequiturIt Does Not Follow

    • Ex: Our university has one of the best faculties in the U.S. because a Nobel Prize winner used to teach here.

    • How does the fact that a Nobel Prize winner used to teach at our university make its present faculty one of the best in the U.S.?


    Non sequitur it does not follow3

    Non SequiturIt Does Not Follow

    • Ex: It’s a beautiful day! We don’t need to be in class.

    • Ex: The professor in the Hawaiian shirt and flip flops must be an easy grader.


    Non sequitur it does not follow4

    Non SequiturIt Does Not Follow

    • Ex: Donald Trump, the billionaire real-estate developer, in considering a run for president in 2000, told an interviewer:

      • “My entire life, I’ve watched politicians bragging about how poor they are, how they came from nothing, how poor their parents and grandparents were. And I said to myself, if they can stay so poor for so many generations, maybe this isn’t the kind of person we want to be electing to a higher office. How smart can they be? They’re morons. Do you want someone who gets to be president and that’s literally the highest paying job he’s ever had?”

    • As a brief glance at U.S history shows, it does not follow that men of small success in the world of commerce are unfit to make sound decisions about matters of state.


    Fallacies

    The End


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