Critical Thinking Lecture 5 1Informal fallacies 1 o

批判性思维 Critical Thinking 第五讲（Lecture 5） 非形式谬误（1）（Informal fallacies 1）

o It is easy for us to make mistakes in our reasoning because we are easily affected by psychological emotions, social and political circumstances (including our interests), and customs and public opinion, and complexity of reasoning itself. o One of the purposes of this course is to learn how to avoid mistakes or fallacies in reasoning. o The first thing we need to do is to identify fallacies.

1. Fallacies in general o A fallacy is a defect in an argument that consists in something other than merely false premises. o A fallacy that involves a mistake in reasoning is sometimes called a non sequitur (which, in Latin, means “it does not follow”).

Two kinds of fallacies: formal and informal o If an argument is unsound or uncogent, then either it has one or more false premises or it commits a fallacy, or both. o A formal fallacy is one that may be identified by merely examining the form or structure of an argument. Fallacies of this kind are found only in deductive arguments.

Example of Formal Fallacies o If apes are intelligent, then apes can solve the puzzles. o Apes can solve the puzzles. o Therefore, apes are intelligent. o This is an invalid argument.

Formal fallacies are identified purely by analyzing the form. o o It has the following form: If P, then Q. Q. Therefore, P. o o Counterexample: If it is a rose, then it is a flower. It is a flower. Therefore, it is a rose.

o Informal fallacies are those that can be detected only by examining the content of the argument.

Examples of informal fallacies o A chess player is a person. o Therefore, a bad chess player is a bad person. o The Brooklyn Bridge is made of atoms. o Atoms are invisible. o Therefore, the Brooklyn Bridge is invisible.

Fallacies of Relevance o The common feature to all the fallacies of relevance is that the premises are logically irrelevant to the conclusion, though they might be psychologically relevant.

1. Appeal to Force o The arguer tries to get his conclusion accepted by a person or persons by threatening that person or those persons. o A girl to her boyfriend: “You should buy me a diamond necklace, otherwise I will end our relationship. ”

o Secretary to boss: I deserve a raise in salary for the coming year. After all, you know how friendly I am with your wife, and I’m sure you wouldn’t want her to find out what’s been going on between you and that sexpot client of yours.

2. Appeal to Pity o Instead of providing the relevant evidence or reason, the arguer tries to evoke sympathy from the audience or the reader to get his conclusion accepted.

o Taxpayer to judge: Your Honor, I admit that I declared thirteen children as dependents on my tax return, even though I have only two. But if you find me guilty of tax evasion, my reputation will be ruined. I’ll probably lose my job, my poor wife will not be able to have the operation that she desperately needs, and my kids will starve. Surely I am not guilty.

3. The Appeal to the People (Emotion) o The arguer tries to get the conclusion accepted by playing on the listeners’ or readers’ desire to be loved, esteemed, admired, valued, or accepted by others or included in a group of people. o Play on/upon 利用

o There are direct and indirect appeal to the people. o Let us concentrate on indirect appeal.

The bandwagon argument o If you don’t do such and such, so and so, you will be left behind or out of the group. o Example: o Of course you want to buy Crest [佳洁士] toothpaste, because 90 percent of Americans brush with Crest.

The appeal to vanity o If you do such and such, so and so, you will be admired, pursued or imitated. o Example: o The Few, the Proud, the Marine.

The appeal to the snobbery o Similar to the appeal to vanity. o A Rolls-Royce [劳斯莱斯] is not for everyone. If you qualify as one of the select few, this distinguished classic may be seen and driven at British Motor Cars, Ltd. (By appointment only, please. )

o Mother to child: You want to grow up and be just like Wonder Woman, don’t you? Then eat your liver and carrots.

4. Argument Against the Person (Argumentum Ad Hominem) o The arguer commits this fallacy if in his argument, he directs his attention to another arguer rather than the second arguer’s argument or position. o There are three kinds of such fallacy: circumstantial, abusive and tu quoque

Ad hominem-abusive o The arguer verbally abuses or attacks another arguer. (offensively or verbal abuse) o Poet Allen Ginsberg has argued in favor of abolishing censorship of pornographic literature. But his arguments are nothing but trash. Ginsberg, you know, is a marijuana -smoking homosexual and a thoroughgoing advocate of the drug culture.

Ad hominem-circumstantial o The arguer discredit the opponent’s argument by alluding to certain circumstances about the opponent. o President George W. Bush argues that we should open up the Arctic National Wildlife Refuge for oil drilling. But Bush just wants to reward his rich cronies in the oil industry who got him elected. Thus, we can hardly take Bush’s argument seriously.

Tu quoque (you too) o Child to parent: Your argument that I should stop stealing candy from the corner store is no good. You told me yourself just a week ago that you, too, stole candy when you were a kid. o The judge has ruled that we are not paying our employees well enough. How can this be right when the judge’s own secretary doesn’t get paid well either?

5. Accident o One commits Accident if one misapplies (incorrectly applies) a general principle to a specific case. o Dogs have four legs. Fido just had one of his legs amputated. So, Fido is not a dog any more.

6. Straw Man o This fallacy is committed when an arguer distorts an opponent’s argument for the purpose of more easily attacking it.

o Mr. Goldberg has argued against prayer in the public schools. Obviously Mr. Goldberg advocates atheism. But atheism is what they used to have in Russia. Atheism leads to the suppression of all religions and the replacement of God by an omnipotent state. Is that we want for this country? I hardly think so. Clearly, Mr. Goldberg’s argument is nonsense.

7. Missing the point (Irrelevant Conclusion) o The premises are supposed to lead to one conclusion but a totally different conclusion is drawn. o Crimes of theft and robbery have been increasing at an alarming rate lately. The conclusion is obvious: we must reinstate the death penalty immediately.

o Certainly Miss Malone will be a capable and efficient manager. She has a great figure, a gorgeous face, and tremendous poise, and she dresses very fashionably.

8. Red Herring o It is committed when the arguer diverts the attention of the reader or listener by changing the subject to a different but sometimes subtly related one. o The arguer tries to draw the audience or readers off right track and then draw a conclusion on a different issue. ).

o There is a good deal of talk these days about the need to eliminate pesticides from our fruits and vegetables. But many of these foods are essential to our health. Carrots are an excellent source of vitamin A, broccoli is rich in iron, and oranges and grapefruits have lots of vitamin C.

o We’ve all heard the argument that too much television is the reason our students can’t read and write. Yet, many of today’s TV shows are excellent. “Seinfeld” explores important issues facing single people, “E. R. ” presents medical professionals in life-and-death situations, and “ 60 minutes” exposes a great variety of scams and illegal practices. Today’s TV is just great!

o. Thank you!