LOGICAL FALLACIES

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Logical fallacies are errors in reasoning. Logicians have identified dozens of specific fallacies. However, we will limit our consideration to the most common ones. Like the other problems encountered in critical thinking, these errors occur when we approach issues carelessly. (The distinction between logical fallacies and the problems discussed in Chapters 6 through 13 is not a rigid one. Some logicians would consider certain of those problems logical fallacies.)

Ø        ILLOGICAL CONCLUSION

For an argument to be valid, the conclusion must follow logically from the premises (assertions). In fact, the conclusion must be inescapable. An illogical conclusion is one that does not follow at all or that does not necessarily follow. Here are some examples.

CONCLUSION: I've got to get even with Mary because she offended me without cause.
COMMENT: Illogical conclusion. You don't have to respond as Mary did. You could choose to overlook or forgive the offense.

CONCLUSION: If guns are outlawed, only outlaws will have guns.
COMMENT: Illogical conclusion. The police and the military would still have guns and, if the law so provided, so would any other people who met the new requirements for ownership.

CONCLUSION: The Soviet government has never given their citizens any freedoms, so their recent moves toward democracy are clearly part of a plan to get us to let down our guard and become vulnerable to attack.
COMMENT: illogical conclusion. The conclusion reached here is one possible conclusion among several. But there is insufficient evidence to consider it probable, let alone certain. The Soviet government may instead be responding to internal social pressures or to harsh economic penalties of collectivism and repression.

Ø        EITHER-OR THINKING

This fallacy consists of believing that the only views one can take of an issue are extreme views. According to this belief, for example, we must be either for abortion on demand or against abortion in all cases; in favor of retaining the welfare system in its present form or abolishing it altogether. Yet it is perfectly possible to endorse abortion in some cases but not in others and to oppose welfare abuses without denying the need for welfare. To deny ourselves the opportunity even to consider moderate views on issues is to condemn ourselves to unreasonableness on most issues. Extreme views are seldom reasonable views.

This does not mean that we should be wishy-washy or compromise matters of principle. If the most sensible view of an issue is total affirmation or rejection, then that is the view we should take. But we should not allow the either-or fallacy to force us to that view.

Ø        ATTACKING THE PERSON

There are times when the character of a person is the issue under discussion; for example, in cases where a member of Congress is being investigated for alleged lawbreaking or ethical violations. In such cases, it is appropriate to focus our argument on the person. However, in cases where the issue is an idea, it is inappropriate to focus on the person.

Consider the issue of whether nuclear power plants are a danger to human beings and the environment. Among the supporters of those plants (as among the opponents) there are, presumably, informed people and uninformed, honest and dishonest, emotionally balanced and emotionally unbalanced. If we find a supporter who is uninformed, dishonest and emotionally unbalanced, what does that tell us about his side of the issue? Nothing at all. It might still be the most reasonable view. The only way to make a decision about an issue is to analyze the issue itself.

Ø        SHIFTING THE BURDEN OF PROOF

Also known as argument from ignorance, this fallacy consists of demanding that others disprove our assertions. Whenever we make an assertion, it is our responsibility to support it, not other people's to refute it. (They may, of course, choose to refute it if they wish.) And the more our assertion departs from what knowledgeable people believe, the greater is our responsibility to support it.

Ø        FALSE CAUSE

It is perfectly natural to wonder "Why did this happen?" in fact, one mark of a critical thinker is that she asks this question more frequently than others do. However, she realizes that mere closeness in time does not prove a cause and effect relationship. In other words, one event can follow another by coincidence and thus be entirely unrelated to it.

The fallacy of false cause occurs when coincidence is ignored. It consists of thinking, "If B occurred after A, A must have caused B." This error is undoubtedly the basis of most superstitions. Misfortune befalls someone shortly after he walks under a ladder, or breaks a mirror, or has a black cat cross his path, and he judges that even to be responsible for the misfortune.

Sam is in the habit of arriving late to English class. Yesterday the professor told him that the next time he was tardy, he would be refused admission. Today Sam got a composition back with a grade of D. He reasons the professor gave him a low grade out of anger over Sam's lateness. Sam has committed the fallacy of false cause. Maybe the professor did lower the grade for that reason, maybe not. Without additional evidence, Sam should withhold judgment.

Ø        STRAW MAN

As the term implies, straw man is an argument without substance. This fallacy consists of pretending one's adversary has said something false and then proceeding to demonstrate that it is false. Suppose you are debating whether legislation should be enacted restricting the sale of assault weapons. You state that you support such legislation because assault weapons are designed, not for hunting or even for self-defense but for killing people, often indiscriminately. Your opponent responds, "So you believe you should decide what weapons are acceptable and what weapons aren't. It's exactly this kind of arrogance by self-appointed social reformers that everyone who lives the constitutions should fear."

Your opponent has committed the straw man fallacy. Perhaps she did so consciously to put you on the defensive. (The best response is to point out what she has done: "First you put irresponsible words in my mouth and then you say I'm irresponsible. I'd prefer to hear your reaction to what I really said."

Ø        IRRATIONAL APPEALS

Irrational appeals urge us to accept ideas at face value or on some other basis than reasonableness. They are considered logical fallacies because they say, in effect, "You don't have to think about this matter – there is no danger of error here." And that is, itself, a serious error. The danger of error always exists, and thinking critically is the best way to minimize that danger.

Irrational appeals usually take one of the following forms:

Appeal to emotion. this appeal urges the uncritical acceptance of strong feelings; for example, love of family or country, fear, resentment, guilt.
Appeal to Tradition or Faith. This appeal urges maintaining past customs or beliefs not because they are applicable to the present situation, but merely because they have always been maintained.
Appeal to Moderation. An appeal to moderation urges a moderate view not because it is the most reasonable view, but merely because it is inoffensive to anyone.
Appeal to Authority. This appeal urges the unquestioning acceptance of an authority's view. The authority may be a person, a book or document, or an agency (such as the Supreme Court).
Appeal to Common Sense. This appeal is often accompanied by such phrases as "everyone knows that," "no reasonable person would deny that," and "it's common sense." (Many ideas that were at one time accepted as common sense – such as sacrificing young virgins to ensure a good harvest and abandoning deformed babies to die – are now recognized as uncommon nonsense or worse.)

Appeals to emotion, tradition, faith, moderation, authority, or common sense are not necessarily irrational. In many cases they are rational – that is, they invite, rather than discourage, critical thinking. Be sure to distinguish between rational and irrational appeals whenever you evaluate issues.

Ø        IDENTIFYING LOGICAL FALLACIES

It's tempting to think that if we find errors, we automatically disprove the conclusion. That's not so. The conclusion may be reasonable in spite of the errors. Whenever you examine an issue remember that, as important as it is to recognize and avoid errors, your main objective is to find the most reasonable, supportable view.

v        APPLICATIONS

1.        Examine each of the following arguments carefully. If you are uninformed about the issue it addresses, do some research. Then decide which view of the issue is most reasonable. Be alert for logical fallacies in the arguments themselves and avoid committing fallacies in your reasoning.
a.        I never vote in national elections. I figure that my vote will be canceled by someone else's. Besides, all politicians are going to rob the public so it doesn't matter who gets elected.
b.        Dog fighting is a sport in which two specially trained dogs (often, but not always, pitbull terriers) do combat until one is killed or badly maimed. It is illegal in most states. But should it be? I say no. if I own a dog, it's my property and I should be able to do whatever I wish with it.
c.        Affirmative action originated as a system to overcome the effects of years of prejudice against minorities. But it has created discrimination against the majority. I favor eliminating affirmative action requirements and returning to the old system. For all its imperfections, it's far better than what we have now.
d.        Whenever Americans buy automobiles, clothing, and electronic equipment from other countries, they undermine American business and hurt American workers. Patriotism demands that we refrain from buying from foreign competitors even when their prices are lower and their quality is higher.
e.        It's absurd to believe in life after death because no one has ever returned form the grave.
f.        Women in the military should be required to undergo the same physical training men do. They should also not be exempted from frontline duty.
g.        In 1982, New York State Social Services officials directed local adoption agencies not to reject applicants solely because they are homosexual or have a history of alcoholism or drug abuse, a criminal record, a dependency on welfare, or a severe emotional or physical handicap.
h.        Every knowledgeable person agrees that the nation's court system is seriously bogged down with cases and that something must be done to alleviate that condition. The best way to do so, I am convinced, is to dispense with the outdated concept of "innocent until proven guilty" and make all those charged with a crime prove their innocence.
i.        It's ironic that during the very time when Pete Rose was being castigated for his alleged gambling on sports events (late spring, 1989), newspapers were filled with stories about Illinois and Pennsylvania lotteries and their respective $62.5 and $115 million jackpots. Millions of people were placing bets on those lotteries, and dozens of other state lotteries, and that was regarded as perfectly legitimate. And yet a great baseball star was being threatened with disgrace and expulsion from the game he loved. The whole fiasco can be explained only in terms of monumental ignorance or hypocrisy.
j.        For the last few decades most Americans have swallowed the liberal line that everyone deserves a college education. As a result, college courses have been watered down and the college degree has been rendered meaningless. It's high time we adopt a more realistic view. College should be reserved for those who have not only taken a demanding high school program, but have excelled in it.
2.        Group discussion exercise: Select one of the cases you analyzed in application 1 and discuss it with two or three of your classmates. Try to reach a consensus, but be careful to avoid committing logical fallacies. Be prepared to present your idea(s) to the class.[/SIZE]

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书名 BEYOND FEELINGS
A GUIDE TO CRITICAL THINKING
by VINCENT RYAN RUGGIERO