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. . What is a fallacy?. A fallacy is an error in reasoningNot the same as being factually wrong.. . . What is a fallacy?. It's possible to draw a false conclusion from factually correct premises. Fallacy = an argument in which the premises do not support the conclusion.. . . Building a Strong Chair (argument).
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1. Argument: Fallacious Arguments
2. What is a fallacy? A fallacy is an error in reasoning
Not the same as being factually wrong.
3. What is a fallacy? It’s possible to draw a false conclusion from factually correct premises.
Fallacy = an argument in which the premises do not support the conclusion.
4. Building a Strong Chair (argument)
Chair legs=premises or reasons
Chair seat = claim or conclusion
5. Building a Strong Chair (argument) The chair can be weak because the wood of the chair legs is rotten (factual error)
OR
Because the legs are not securely attached to the seat of the chair.
6. Deductive argument Premises provide complete support for the conclusion
If all premises are true, conclusion must be true.
7. Example of Deductive Argument All men are mortal
Socrates is a man
Socrates is mortal
A deductive argument is valid if it is impossible for both its premises to be true and its conclusion to be false.A deductive argument is valid if it is impossible for both its premises to be true and its conclusion to be false.
8. Example of Valid, But Unsound Deductive Argument All Greeks are philosophers
Socrates is a Greek
Socrates is a philosopher
An argument can be valid even though the premises are false. This argument is valid, but it is not sound.
An argument can be valid even though the premises are false. This argument is valid, but it is not sound.
9. Example of a deductive fallacy Premise 1: All mammals give birth to live young
Premise 2: The seahorse gives birth to live young
Conclusion: the seahorse is a mammal A fallacy is an error in reasoning - the argument is invalid.A fallacy is an error in reasoning - the argument is invalid.
10. Inductive Argument The premises of an inductive argument provide some degree of support for the conclusion, but they do not guarantee its truth.
11. Example of Inductive Argument- strong or cogent Premise 1: X% percentage of males are color-blind
Premise 2: Dan is male
Conclusion: The probability that Dan is color-blind corresponds to X. Inductive arguments cannot be valid, but they can be strong or “cogent.” This one is strong.Inductive arguments cannot be valid, but they can be strong or “cogent.” This one is strong.
12. Example of Inductive Argument- weak Premise 1: In our study, 80% of women preferred the pink widget to an identical blue widget, compared to 24% of men.
Conclusion: Women like pink. Inductive arguments cannot be valid, but they can be strong or “cogent.” This one is strong.Inductive arguments cannot be valid, but they can be strong or “cogent.” This one is strong.
13. An Inductive Fallacy Premise: I have seen lots of swans and they were all white
Conclusion: There are no black swans
14. Common Rhetorical Fallacies See nizkor.org/features/fallacies for a more complete list
Review WLTC section on fallacies
The following are the ones you should especially guard against.
15. Appeal to Authority Joe: Vitamin C cures baldness
Fred: That’s a ridiculous claim!
Joe: I read it here in this book by a Nobel prize-winning nuclear physicist. He’s really smart, so it must be true.
16. Appeal to Authority is likely a fallacy if: The authority has insufficient expertise in the area in question
There is not a sufficient consensus among experts in the area in question
The authority appealed to has a significant bias
Authority must be named, the area of expertise must be legitimate (e.g. not tarot reader)
Appeal to Authority can be a good argument, but is not usually the strongest or best.Authority must be named, the area of expertise must be legitimate (e.g. not tarot reader)
Appeal to Authority can be a good argument, but is not usually the strongest or best.
17. Personal Attack (ad hominem) An ad hominem is an argument in which a claim is rejected based on an irrelevant fact about the person making the claim.
18. Personal Attack (ad hominem) Jane: I believe this health care bill will help small business and the working poor.
Joe: All you Democrats want is a handout!
19. Equivocation (Doublespeak,Bait and Switch) Misleading use of a word or phrase that has more than one meaning or sense.
20. Equivocation “I don’t believe in evolution, because it’s only a theory.”
21. Straw Man Ignoring the actual argument and arguing against a distorted version of the position.
22. Straw Man Evolution says that everything evolves from something else. So if we evolved from monkeys, why are there still monkeys?
23. Appeal to Fear/Emotion Buy our green product. (picture of cute fluffy bunny)
I think critics of the Iraq war should support our troops. Think of all the returning vets who were yelled at and spat on during the Vietnam war.
If this health care bill passes, it will be a sign that the End Times are near.
24. Begging the Question The premises used to support the claim include a claim that the conclusion is true, or assume that the conclusion is true.
25. Begging the Question Jane is innocent, because she would never do something like that.
Bo is the cutest White House pet ever, because all the other ones were unappealing.
26. Begging the Question A better name for this fallacy might be “assuming the initial point” or “circular reasoning” because the phrase is often used informally to mean “suggests the question.”
Joe’s Facebook status begged the question of what I should get him for his birthday.
(not a fallacy or even an argument)
27. Hasty Generalization Make an inductive conclusion based on too small a sample.
“Your inductive leap is too great.”
28. Hasty Generalization 16 out of 20 Asians preferred higher income over more time for leisure, compared to 8 out of 20 Europeans. Therefore, Europeans are more fun-loving, and Asians are more industrious.
29. Poisoning the Well Providing information, usually negative, as an attempt to bias the audience against the speaker.
Unfavorable definitions that prevent disagreement. Usually pre-emptive - offering an argument that invalidates any further argument.Usually pre-emptive - offering an argument that invalidates any further argument.
30. Poisoning the Well “Only a heartless, selfish person would oppose universal health care.”
“As a man, you can’t possibly understand the questions surrounding abortion.”