Fallacies Flaws in the Structure of an Argument. What are fallacies? Fallacies are defects in an...

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Fallacies Fallacies Flaws in the Structure of an Flaws in the Structure of an Argument Argument

Transcript of Fallacies Flaws in the Structure of an Argument. What are fallacies? Fallacies are defects in an...

Page 1: 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.

FallaciesFallaciesFlaws in the Structure of an Flaws in the Structure of an

ArgumentArgument

Page 2: 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.

What are fallacies?What are fallacies?

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

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

Page 3: 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.

Formal FallaciesFormal Fallacies Formal fallacies are only found in Formal fallacies are only found in deductive deductive

argumentsarguments..

Deductive arguments are supposed to be air-Deductive arguments are supposed to be air-tight. tight.

For a deductive argument to be valid, it must be For a deductive argument to be valid, it must be absolutely impossible for both its absolutely impossible for both its premisespremises to be to be true and its true and its conclusionconclusion to be false. With a good to be false. With a good deductive argument, that simply cannot happen; deductive argument, that simply cannot happen; the truth of the premises entails the truth of the the truth of the premises entails the truth of the conclusion.conclusion.

Page 4: 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.

Formal FallaciesFormal Fallacies

The classic example of a deductively valid The classic example of a deductively valid argument is:argument is:– 1. All men are mortal. (premise)1. All men are mortal. (premise)– 2. Socrates is a man. (premise)2. Socrates is a man. (premise)– 3. Therefore Socrates is mortal. (guaranteed conclusion)3. Therefore Socrates is mortal. (guaranteed conclusion)

It is simply not possible that both (1) and It is simply not possible that both (1) and (2) are true and (3) is false, so this (2) are true and (3) is false, so this argument is deductively valid.argument is deductively valid.

Page 5: 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.

Formal FallaciesFormal Fallacies

Any deductive argument that fails to meet this Any deductive argument that fails to meet this very highvery high standardstandard commits a logical error, and commits a logical error, and so, so, technicallytechnically, is fallacious. , is fallacious.

This includes many arguments that we would This includes many arguments that we would usually accept as good arguments, arguments usually accept as good arguments, arguments that make their conclusions that make their conclusions highly probablehighly probable but but not certain. not certain.

Arguments that aren’t deductively valid are said Arguments that aren’t deductively valid are said to commit a “formal fallacy.”to commit a “formal fallacy.”

Page 6: 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.

Formal FallaciesFormal Fallacies

Example of a deductive argument with a formal Example of a deductive argument with a formal fallacy:fallacy:

1. All humans are mammals. (premise)1. All humans are mammals. (premise)2. All cats are mammals. (premise)2. All cats are mammals. (premise)3. All humans are cats. (conclusion) 3. All humans are cats. (conclusion)

Both premises in this argument are true but the Both premises in this argument are true but the conclusion is false. The defect is a formal fallacy conclusion is false. The defect is a formal fallacy and can be demonstrated by reducing the and can be demonstrated by reducing the

argument to its bare structure:argument to its bare structure: 1. All A are C1. All A are C2. All B are C2. All B are C

3. All A are B3. All A are B

Page 7: 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.

Formal FallaciesFormal Fallacies

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

(guaranteed conclusion)(guaranteed conclusion)

Page 8: 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.

Formal FallaciesFormal Fallacies

– All chickens are feathered animals. (premise)All chickens are feathered animals. (premise)– Quacko is a feathered animal. (premise)Quacko is a feathered animal. (premise)– Therefore Quacko is a chicken. (non-Therefore Quacko is a chicken. (non-

guaranteed conclusion)guaranteed conclusion) This argument commits a formal fallacy in This argument commits a formal fallacy in

that its form doesn’t that its form doesn’t guaranteeguarantee the truth the truth of its conclusion, even if the initial of its conclusion, even if the initial premises are true.premises are true.

Page 9: 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.

The Problem of Conclusiveness in an The Problem of Conclusiveness in an ArgumentArgument

Real-world arguments address contestable Real-world arguments address contestable issues of truth and value that cannot be issues of truth and value that cannot be resolved with mathematical certainty. resolved with mathematical certainty.

Disputants can create only more or less Disputants can create only more or less persuasive arguments, never conclusive persuasive arguments, never conclusive ones.ones.

Page 10: 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.

The Problem of Conclusiveness in an The Problem of Conclusiveness in an ArgumentArgument

Real-world Arguments

Unpersuasive PersuasiveConclusive

•Logically sound•Air-tight argument

Page 11: 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.

Informal FallaciesInformal Fallacies

They are flaws in the structure of an They are flaws in the structure of an argument.argument.

They sometimes make flawed reasoning They sometimes make flawed reasoning seem deceptively persuasive.seem deceptively persuasive.

Page 12: 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.

Why Study Informal Why Study Informal Fallacies?Fallacies?

Knowledge of informal fallacies is most useful Knowledge of informal fallacies is most useful when we run across arguments that we “know” when we run across arguments that we “know” are wrong, but we cannot quite say why.are wrong, but we cannot quite say why.

Knowledge of informal fallacies can help you Knowledge of informal fallacies can help you locate specific weaknesses in others’ arguments . locate specific weaknesses in others’ arguments . . . and in your own!. . and in your own!

Page 13: 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.

Informal Fallacies: Three Informal Fallacies: Three CategoriesCategories

1.1. Fallacies of PathosFallacies of Pathos

2.2. Fallacies of EthosFallacies of Ethos

3.3. Fallacies of LogosFallacies of Logos

Page 14: 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 of PathosFallacies of Pathos Rest on flaws in the way an argument Rest on flaws in the way an argument

appeals to the audience’s appeals to the audience’s emotionsemotions and and valuesvalues– Argument to the PeopleArgument to the People– Appeal to IgnoranceAppeal to Ignorance– Appeal to PopularityAppeal to Popularity– Appeal to PityAppeal to Pity– Red HerringRed Herring

Page 15: 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.

Argument to the PeopleArgument to the PeopleAppeal to Stirring SymbolsAppeal to Stirring Symbols

Appeal to the fundamental beliefs, biases, Appeal to the fundamental beliefs, biases, and prejudices of the audience in order to and prejudices of the audience in order to sway opinion through a feeling of sway opinion through a feeling of solidarity among those of a group.solidarity among those of a group.

Page 16: 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.

Argument to the PeopleArgument to the PeopleAppeal to Stirring SymbolsAppeal to Stirring Symbols

The stirring symbol of the American flag The stirring symbol of the American flag – Allegiance to nationalistic valuesAllegiance to nationalistic values– Solidarity of American citizensSolidarity of American citizens

Ex: Joe Politician delivering a speech while Ex: Joe Politician delivering a speech while wearing a suit made out material patterned with wearing a suit made out material patterned with the American flag.the American flag.

Ex: Marilyn Manson wiping his butt on an Ex: Marilyn Manson wiping his butt on an American flag.American flag.

Page 17: 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.

Appeal to IgnoranceAppeal to Ignorance

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

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

Page 18: 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.

Appeal to IgnoranceAppeal to Ignorance

Ex: Researchers have not conclusively shown Ex: Researchers have not conclusively shown that there is no monster at the bottom of Loch that there is no monster at the bottom of Loch Ness; therefore, we should expect to see the Ness; therefore, we should expect to see the monster at any time.monster at any time.

Ex: There must be intelligent life on other Ex: There must be intelligent life on other planets. No one has proven that there isn’t.planets. No one has proven that there isn’t.

Page 19: 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.

Appeal to IgnoranceAppeal to Ignorance

Ex: Genetically modified organisms must be Ex: Genetically modified organisms must be dangerous to our health because science has not dangerous to our health because science has not proved that they are safe.proved that they are safe.

Ex: Jones must have used steroids to get those Ex: Jones must have used steroids to get those bulging muscles because he cannot prove that he bulging muscles because he cannot prove that he has not used steroids.has not used steroids.

Page 20: 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.

Appeal to PopularityAppeal to PopularityThe Bandwagon AppealThe Bandwagon Appeal

The argument rests on the assertion that since The argument rests on the assertion that since everybody else is doing something, you should do everybody else is doing something, you should do it too.it too.

These appeals are fallacious because the These appeals are fallacious because the popularitypopularity of something is irrelevant to its actual of something is irrelevant to its actual meritsmerits..

These appeals are common in advertising where These appeals are common in advertising where the claim that a product is popular substitutes for the claim that a product is popular substitutes for evidence of the product’s excellence.evidence of the product’s excellence.

Page 21: 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.

Appeal to PopularityAppeal to PopularityThe Bandwagon AppealThe Bandwagon Appeal

Ex: All the popular, cool kids have tattoos; Ex: All the popular, cool kids have tattoos; therefore, I should get a tattoo.therefore, I should get a tattoo.

Ex: Everybody who has a Facebook page has a Ex: Everybody who has a Facebook page has a lot of friends; therefore, I should make a lot of friends; therefore, I should make a Facebook page.Facebook page.

Page 22: 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.

Appeal to PopularityAppeal to PopularityThe Bandwagon AppealThe Bandwagon Appeal

Ex: Living together before marriage is the Ex: Living together before marriage is the right thing to do because most couples are right thing to do because most couples are now doing it.now doing it.

Ex: You should buy a Toyota Camry Ex: You should buy a Toyota Camry because it is the best-selling car in the because it is the best-selling car in the world.world.

Page 23: 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.

Appeal to PityAppeal to Pity

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

Page 24: 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.

Appeal to PityAppeal to Pity

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

Page 25: 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.

Appeal to PityAppeal to Pity Ex: “Honorable Judge, I should not be fined $250 Ex: “Honorable Judge, I should not be fined $250

for driving 85 mph in a 25 mph zone because I for driving 85 mph in a 25 mph zone because I was distraught from hearing the news of my was distraught from hearing the news of my brother’s illness and was rushing to see him in brother’s illness and was rushing to see him in the hospital.”the hospital.”

Page 26: 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.

Red HerringRed Herring

Refers to the practice of throwing an Refers to the practice of throwing an audience off track by raising an unrelated audience off track by raising an unrelated or irrelevant point. or irrelevant point.

The name derives from the practice of using a red The name derives from the practice of using a red herring (a very smelly fish) to throw dogs off from herring (a very smelly fish) to throw dogs off from a scent that they are supposed to be tracking.a scent that they are supposed to be tracking.

Page 27: 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.

Red HerringRed Herring

Ex: Jack’s girlfriend asks, “Where were you last Ex: Jack’s girlfriend asks, “Where were you last night?” Jack answers, “I sure am glad to see you. night?” Jack answers, “I sure am glad to see you. You look extra beautiful today!” You look extra beautiful today!”

Ex: Question to politician, “What’s your stand on Ex: Question to politician, “What’s your stand on gun control?” Politician’s reply, “I’m for family gun control?” Politician’s reply, “I’m for family values.”values.”

Page 28: 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.

Red HerringRed Herring

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

Page 29: 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 of EthosFallacies of Ethos

Fallacies of Ethos = Rest on a flawed Fallacies of Ethos = Rest on a flawed relationship between the argument and relationship between the argument and the the charactercharacter of those involved in the of those involved in the argument. argument.

Often these fallacies attack character or Often these fallacies attack character or use character instead of evidence for use character instead of evidence for proof.proof.

Page 30: 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.

Appeal to False AuthorityAppeal to False Authority

The arguer appeals to the authority of a popular The arguer appeals to the authority of a popular person rather than a knowledgeable one.person rather than a knowledgeable one.

Many advertisements are based on this fallacy.Many advertisements are based on this fallacy.

Testimony to support an argument should come Testimony to support an argument should come from a person competent in the field. from a person competent in the field.

Page 31: 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.

Appeal to False AuthorityAppeal to False Authority Kobe Bryant says that Wheaties cereal keeps him Kobe Bryant says that Wheaties cereal keeps him

on his game; therefore, Wheaties cereal is a good on his game; therefore, Wheaties cereal is a good cereal.cereal.

Real evidence about the quality of Wheaties Real evidence about the quality of Wheaties cereal would include specific information about its cereal would include specific information about its nutritional content rather than testimony from a nutritional content rather than testimony from a hired athlete.hired athlete.

Page 32: 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.

Appeal to False AuthorityAppeal to False Authority

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

Page 33: 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.

Ad HominemAd HominemAppeal to the personAppeal to the person

Arguments that attack the character Arguments that attack the character of the arguer rather than the of the arguer rather than the argument itselfargument itself– Name-calling (referring to a disputant by Name-calling (referring to a disputant by

unsavory names)unsavory names)– Appeal to prejudice (applying ethnic, racial, Appeal to prejudice (applying ethnic, racial,

gender, or religious slurs to an opponent)gender, or religious slurs to an opponent)– Guilt by association (linking the opposition to Guilt by association (linking the opposition to

extremely unpopular groups or causes)extremely unpopular groups or causes)– Poisoning the Well (discrediting an opponent or Poisoning the Well (discrediting an opponent or

an opposing view in advance)an opposing view in advance)

Page 34: 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.

Ad HominemAd HominemAppeal to the personAppeal to the person

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

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

Page 35: 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.

Ad HominemAd HominemAppeal to the personAppeal to the person

Name-callingName-calling– Ex: OJ Simpson claims that he is innocent, but Ex: OJ Simpson claims that he is innocent, but

he’s a wife beater.he’s a wife beater.

– Ex: Hugh Hefner, founder of Ex: Hugh Hefner, founder of PlayboyPlayboy magazine, has argued against the censorship magazine, has argued against the censorship of pornography. But Hefner is an immature, of pornography. But Hefner is an immature, self-indulgent millionaire who never outgrew self-indulgent millionaire who never outgrew the adolescent fantasies of his youth. His the adolescent fantasies of his youth. His argument is worthless.argument is worthless.

Page 36: 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.

Ad HominemAd HominemAppeal to the personAppeal to the person

Appeal to prejudiceAppeal to prejudice– Ex: Because he is extremely wealthy, our Ex: Because he is extremely wealthy, our

mayor cannot properly represent this city.mayor cannot properly represent this city.

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

Page 37: 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.

Ad HominemAd HominemAppeal to the personAppeal to the person

Guilt by AssociationGuilt by Association– Ex: Of course you support medical marijuana. Ex: Of course you support medical marijuana.

All of your friends are a bunch of pot-head All of your friends are a bunch of pot-head hippies.hippies.

– Ex: Professor Smith has argued against the Ex: Professor Smith has argued against the theory of evolution. But he’s a member of the theory of evolution. But he’s a member of the Communist Bikers’ Association. I refuse to Communist Bikers’ Association. I refuse to listen to him!listen to him!

Page 38: 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.

Ad HominemAd HominemAppeal to the personAppeal to the person

Poisoning the WellPoisoning the Well

Ex: You are told, prior to meeting him, that your Ex: You are told, prior to meeting him, that your friend’s boyfriend is a poseur and a mooch. friend’s boyfriend is a poseur and a mooch. When you meet him, everything you hear him say When you meet him, everything you hear him say is tainted.is tainted.

Ex: Before I leave the floor to the next speaker, I Ex: Before I leave the floor to the next speaker, I must remind you that persons who oppose my must remind you that persons who oppose my plan do not have the best interests of the working plan do not have the best interests of the working people in their hearts.people in their hearts.

Page 39: 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.

Straw ManStraw Man

Greatly oversimplifying an opponent’s Greatly oversimplifying an opponent’s argument in order to make it easier to argument in order to make it easier to refute or ridiculerefute or ridicule

Diverts attention from the real issueDiverts attention from the real issue

The name comes from the practice of stuffing dummies and The name comes from the practice of stuffing dummies and scarecrows with straw. When one attacks an opponent by scarecrows with straw. When one attacks an opponent by putting words into the opponent’s mouth, one makes up a putting words into the opponent’s mouth, one makes up a “dummy” position. But just as beating up a scarecrow “dummy” position. But just as beating up a scarecrow doesn’t demonstrate any athletic accomplishment, beating doesn’t demonstrate any athletic accomplishment, beating up a “straw man” in an argument doesn’t demonstrate up a “straw man” in an argument doesn’t demonstrate anything.anything.

Page 40: 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.

Straw Man Straw Man

Ex: You many think that levying confiscatory Ex: You many think that levying confiscatory taxes on homeless people’s cardboard dwellings taxes on homeless people’s cardboard dwellings is the surest way out of a recession, but I don’t.is the surest way out of a recession, but I don’t.

Ex: While my opponent would like to empty our Ex: While my opponent would like to empty our prisons of serial killers, I hold to the sacred prisons of serial killers, I hold to the sacred principles of compensatory justice.principles of compensatory justice.

Page 41: 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 of LogosFallacies of Logos

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

Page 42: 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.

Hasty GeneralizationHasty Generalization

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

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

Page 43: 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.

Hasty GeneralizationHasty Generalization

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

Page 44: 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.
Page 45: 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.

Post Hoc, Ergo Propter HocPost Hoc, Ergo Propter HocAfter This, Therefore Because of ThisAfter This, Therefore Because of This

Occurs when a sequential relationship is Occurs when a sequential relationship is mistaken for a causal relationshipmistaken for a causal relationship

Confusing correlation for causeConfusing correlation for cause Ex: Event A occurred before Event B; Ex: Event A occurred before Event B;

therefore, Event A must have caused therefore, Event A must have caused Event B.Event B.

Page 46: 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.

Post Hoc, Ergo Propter HocPost Hoc, Ergo Propter HocAfter This, Therefore Because of ThisAfter This, Therefore Because of This

Ex: Governor X took office in 2008. In Ex: Governor X took office in 2008. In 2009, the state suffered a severe 2009, the state suffered a severe recession. Therefore, Governor X should recession. Therefore, Governor X should not be re-elected.not be re-elected.

Page 47: 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.

Post Hoc, Ergo Propter HocPost Hoc, Ergo Propter HocAfter This, Therefore Because of ThisAfter This, Therefore Because of This

Superstition is often based on this fallacy.Superstition is often based on this fallacy.

Ex: Since I walked under that ladder yesterday, Ex: Since I walked under that ladder yesterday, I’ve lost my wallet and received a speeding ticket.I’ve lost my wallet and received a speeding ticket.

Ex: Everything was going fine until the lunar Ex: Everything was going fine until the lunar eclipse last month; that’s why the economy is in eclipse last month; that’s why the economy is in trouble.trouble.

Page 48: 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.

Begging the QuestionBegging the QuestionCircular ReasoningCircular Reasoning

Supporting a claim with a reason that Supporting a claim with a reason that simply restates the claim in different simply restates the claim in different wordswords– Ex: Bungee-jumping is dangerous because it’s Ex: Bungee-jumping is dangerous because it’s

unsafe.unsafe.

– Ex: Women should not be permitted to join Ex: Women should not be permitted to join men’s clubs because the clubs are for men men’s clubs because the clubs are for men only.only.

Page 49: 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.

Begging the QuestionBegging the QuestionCircular ReasoningCircular Reasoning

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

Page 50: 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.

False Dilemma – Either/OrFalse Dilemma – Either/Or

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

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

Often one of the choices is made to seem Often one of the choices is made to seem unacceptable , so the only remaining option is the unacceptable , so the only remaining option is the other choice.other choice.– Ex: It’s my way or the highway.Ex: It’s my way or the highway.

Page 51: 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.

False Dilemma – Either/OrFalse Dilemma – Either/Or

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

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

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

Page 52: 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.

False Dilemma – Either/OrFalse Dilemma – Either/Or

Page 53: 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.

Slippery SlopeSlippery Slope

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

Often functions as a scare tacticOften functions as a scare tactic

Page 54: 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.

Slippery SlopeSlippery Slope

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

Page 55: 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.

Slippery SlopeSlippery Slope

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

Page 56: 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.

False AnalogyFalse Analogy

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

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

Page 57: 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.

False AnalogyFalse Analogy

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

Page 58: 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.

False AnalogyFalse Analogy

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

Page 59: 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.

False AnalogyFalse Analogy

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

Page 60: 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.

False AnalogyFalse Analogy

Page 61: 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.

Non SequiturNon SequiturIt Does Not FollowIt Does Not Follow

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

The arguer seems to make an inexplicably The arguer seems to make an inexplicably illogical leap.illogical leap.

Page 62: 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.

Non SequiturNon SequiturIt Does Not FollowIt Does Not Follow

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

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

Page 63: 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.

Non SequiturNon SequiturIt Does Not FollowIt Does Not Follow

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

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

Page 64: 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.

Non SequiturNon SequiturIt Does Not FollowIt Does Not Follow

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

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

Page 65: 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.

Non SequiturNon SequiturIt Does Not FollowIt Does Not Follow

Ex: Donald Trump, the billionaire real-estate Ex: Donald Trump, the billionaire real-estate developer, in considering a run for president in developer, in considering a run for president in 2000, told an interviewer:2000, told an interviewer:– “ “My entire life, I’ve watched politicians bragging about how poor they My entire life, I’ve watched politicians bragging about how poor they

are, how they came from nothing, how poor their parents and 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 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 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. 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 Do you want someone who gets to be president and that’s literally the highest paying job he’s ever had?”highest paying job he’s ever had?”

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

Page 66: 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.
Page 67: 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.
Page 68: 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.