What is a logical fallacy?

Transcription

1 Logical Fallacies

2 What is a logical fallacy? An error in reasoning that undermines or invalidates an argument. Logical fallacies are fairly common but must be avoided in order to produce strong, reliable arguments.

3 Common Fallacies There are many fallacies, but let s just look at a few.

4 Post Hoc Other names: Faulty Causality Definition: Confusing correlation with causation Formula: because B comes after A, A caused B Example: After the teacher starting giving more tests, cheating in class became more common. Therefore, having more tests causes more cheating.

5 Slippery Slope Other names: The Camel s Nose Fallacy Definition: Assuming one action will lead to a set chain of consequences Formula: If A, then B, and if B, then C Example: If he does not study for this test, he will fail it, and then he will fail the class. If he fails the class, he will never get into a good college or get a good job.

6 Begging the Question Other names: Circular Reasoning is one way to do this Definition: asks the audience to simply accept the conclusion without providing real evidence for the premise Formula: A is B because A. Example: Freedom of speech is important because people should be able to speak freely.

7 Hasty Generalization Other names: Dicto Simpliciter or Jumping to Conclusions Definition: Drawing a conclusion based on insufficient or biased evidence Formula: Based on A, B, and C, D-Z must also be the same. Example: I heard that three other people made an A on their project. Therefore, most people in the class must have made an A on the project.

8 PATHOS Appeal to Fear Other names: Scare Tactics Definition: Using fear as the primary reason a claim should be accepted as true Formula: A is a something to fear; therefore B should be implemented to prevent A. Example: If your candidate is elected, this country will go to pieces. Therefore, you should elect my candidate instead!

9 Argument from Ignorance Other names: Appeal to a Lack of Evidence Definition: Saying that since you cannot disprove something, it must be true. Formula: A must be true because no one can prove it is not. Example: Ghosts must be real because no one has been able to prove that they are not!

10 Red Herring Other names: Ignorantio Elenchi Definition: Distracting from the claim or counterclaims by bringing up a side issue Formula: A might be true, but B is also an issue. Example: Yes, I probably should have done my homework, but there are so many other students out there breaking all kinds of school rules!

11 Straw Man Other names: A kind of Red Herring argument Definition: Oversimplifying an opponent's viewpoint and then knocking down that hollow argument Formula: My opposition s position A is extreme or absurd and must be untrue. Example: Speaker 1: "The state should increase funding to unemployed single mothers because they need money to provide medical care for their children." Speaker 2: "My opponent believes that lazy, jobless parasites should get a free ride from the tax money of hard-working honest citizens. He s wrong because

12 PATHOS Appeal to Ridicule Other names: Appeal to Mockery, Horse Laugh Definition: Similar to Straw Man, an opposing view is presented as absurd or ridiculous Formula: Person 1 claims that A is true. Person 2 makes A look ridiculous, by misrepresenting A. Therefore, A is false. Example: Sure, you can join that club...if you want to look like an idiot!

13 False Dichotomy Other names: False Dilemma, Either/Or Fallacy Definition: Oversimplifying an argument by saying there are only two options Formula: We can either do A, or B will happen. Example: You can either go to the party or never have a chance at a social life.

14 ETHOS Ad Hominem Other names: Poisoning the Well, Personal Attack Definition: Attacking the person who makes an argument instead of the argument itself Formula: Because my opponent is -negative trait-, his claim must be untrue. Example: Jason can t be the team captain because he is unattractive and a little overweight.

15 ETHOS Argument from Authority Other names: Appeal to Improper Authority Definition: Assuming an argument is true because of who is saying it when their status suggests no expertise Formula: Because -authority- says so, A must be true. Example: I m going to vote for that candidate because my favorite band said that people should!

16 PATHOS Ad Populum Other names: Bandwagon is a common type Definition: Assuming people should do/believe something in order to be accepted by the majority Formula: Because so many people believe A, A must be true Example: 70% of people say they would vote for this candidate, so you should vote for her too!

17 Testing for Logical Fallacies Some guidelines from UNC Chapel Hill s Writing Center

18 When looking... Pretend you disagree with the conclusion you see. What parts of the argument would now seem fishy to you? List the main points; under each one, list the evidence for it. You realize there is no good evidence for a particular claim, or it may help you look more critically at the evidence used. Be aware that broad claims need more proof than narrow ones. Claims that use sweeping words like all, none, every, always, never, etc. require a lot more proof than less-sweeping claims Double check characterizations of others, especially opponents, to be sure they are accurate and fair.