Errors in Logic Often Found in Persuasive Texts

Transcription

1 Errors in Logic Often Found in Persuasive Texts

2 A fallacy is an error in logical reasoning in an argument or a persuasive text. This isn t the same as a factual error. FALLACY FACTUAL ERROR 4 out of 5 dentists recommend Chewy Brand Gum Chewing gum is made out of Silly Putty

3 There are many different types of fallacies, and readers should be able to identify fallacies when they occur in text. Hasty Generalization Ad Hominem Exaggeration Appeal to Authority Post Hoc Appeal to Emotion Begging the Question

4 One of the most common forms of fallacy is called an ad hominem argument. Literally, ad hominem means against the person. Instead of using logic in an argument, sometimes people attack their opponent. That s effective, but fallacious!

5 EXAMPLE: Teacher: Education is important. We should spend more to improve our schools. Student: Of course you think that. You re a teacher.

6 Another common fallacy is the Hasty Generalization. That s when a person makes sweeping statements based on just a little evidence. Example: Every swan I ve ever seen was white. Therefore, all swans must be white.

7 Sometimes the breakdown in logic is just funny...

8 A post hoc fallacy involves attributing a cause and effect relationship without adequate evidence. (Which is similar to a hasty generalization.) Example: My car was running fine until Jimmy borrowed it. Now it makes a funny noise. He must have done something to it.

9 One of the most common fallacies that comes up in advertising is the Appeal to Authority. Just because somebody famous has an opinion, that doesn t make it true!

10 Similarly, just because a doctor or a dentist says something, that doesn t make it true, either!

11 This is also called the Bandwagon Fallacy, because people are encouraging you to jump on the bandwagon. Everybody else is doing it! All the cool kids are doing it! Don t you want to be like everybody else?

12 I was sick with a terrible cold for several days. Then I took some vitamin C, and I got better. Therefore vitamin C is a cure for colds.

13 I was sick with a terrible cold for several days. Then I took some vitamin C, and I got better. Therefore vitamin C is a cure for colds. This is a post hoc fallacy. If you ve been sick for several days, you probably would have gotten better soon anyway!

14 Fox News criticized a recent report on climate change, saying that they did not report their numbers accurately. But then, you d expect Fox News to find a way to attack the research on climate change.

15 Fox News criticized a recent report on climate change, saying that they did not report their numbers accurately. But then, you d expect Fox News to find a way to attack the research on climate change. This is a classic ad hominem attack! Just because Fox News has a bias doesn t mean they re wrong!

16 My opponent in this election has suggested that cutting business taxes could improve the economy. Do I really need to point out that big businesses have paid for his campaign?

17 My opponent in this election has suggested that cutting business taxes could improve the economy. Do I really need to point out that big businesses have paid for his campaign? This is another ad hominem attack. Getting money does not automatically make a person wrong!

18 Four out of five dentists who chew gum recommend Trident.

19 Four out of five dentists who chew gum recommend Trident. A classic appeal to authority. And how many dentists who DON T chew gum would recommend Trident?

20 Grades in school don t mean anything. Benny is an idiot, and he makes straight-as!

21 Grades in school don t mean anything. Benny is an idiot, and he makes straight-as! A hasty generalization. There may be a lot of reasons why Benny makes good grades.

22 There s nothing wrong with speeding. Everybody does it!

23 There s nothing wrong with speeding. Everybody does it! An appeal to popularity. If all your friends were jumping off a bridge, would you do that too???