Chapter 5 Fallacies - Lecture notes 4 PDF

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Chapter 5 Fallacies  A fallacy is a defect in an argument. Fallacies occur in both deductive and inductive arguments. An argument that has a fallacy is unsound or uncogent.  A formal fallacy results from an invalid argument form. Only deductive arguments can have formal fallacies. If the citizens of a country are to be free then they must arm themselves for protection. The citizens of this country have armed themselves for protection. Therefore, the citizens of this country are free. If A then B. B Therefore, A. (Affirming the Consequent) An informal fallacy is detected by looking at the content of the argument. The Brooklyn Bridge is made of atoms. Atoms are invisible. Therefore, the Brooklyn Bridge is invisible.

Fallacies of Irrelevant Premises  These arguments have premises that are logically irrelevant to the conclusion (even though they may seem psychologically relevant). Genetic Fallacy The reason given to believe that a claim is true or false is because of its origin. Russell’s idea about tax hikes came to him in a dream so it must be worthless.

You cannot trust what Chloe says about her family, she’s a pathological liar.

Ad Hominem (Appeal to the Person)  An ad hominem fallacy occurs when one claims that we shouldn’t believe an argument because of some property about the arguer himself.  Character Jack says that smoking in bars should be legal but he’s an idiot.

Motives Jack says that smoking in bars should be legal but he’s just worried that he’ll lose his job if the smokers go elsewhere. Circumstances Jack says that smoking in bars should be legal but he’s a smoker so of course he’d say that. Tu quoque (“you too”) Jack says that smoking in bars should be legal but he doesn’t allow smoking in his home so you shouldn’t believe him. Composition  The fallacy of composition occurs when one falsely claims that the attributes of the parts can be transferred to the attribute of the whole.  Each atom in this piece of chalk is invisible. Therefore, the chalk is invisible.  Each atom in this piece of chalk has mass. Therefore, the chalk has mass. Division  With the fallacy of division one incorrectly attributes the property of the class to the individuals in the class. Wild apes are going extinct so this wild ape is going extinct. The average Canadian family has 2.3 children. The Smith family is an average Canadian family. The Smith family has 2.3 children. The fallacies of composition and division are often found in statistical arguments. The average small investor invests $2000/year in the stock market. The average large investor invests $100 000/year. Therefore, large investors as a group invest more than the group of small investors.

Equivocation When our belief in the conclusion depends on the fact that a word or phrase is used in two different senses, then the fallacy of equivocation has been committed. I have a right to smoke outdoors if I want to.

Therefore, smoking outdoors is the right thing to do. Six is an odd number of legs for a horse. Odd numbers cannot be divided by two. Six cannot be divided by two. Newspapers should print stories that are in the public interest. Rumors about sex scandals are in the public interest. Newspapers should print rumors about sex scandals. Man is the only rational animal, and no woman is a man, so women are not rational. Appeal to Popularity In this fallacy the arguer claims that a statement is true because a substantial number of people believe it to be true. The vast majority of Canadians believe that the long gun registry is a waste of money. So it is. Sherry received the most votes so she should be crowned prom queen. - Not a fallacy because she needs votes to be prom queen Appeal to Common Practice In this case the fallacy occurs because of what people do instead of what they believe. Fords are the most reliable cars on the road. Most people own a Ford. - Appeal to their actions/behavior

Appeal to Tradition This fallacy occurs when we are asked to believe that a claim is true or false simply because it is part of a tradition. -

Appeal to belief or action done for a long time

Acupuncture has been used for a thousand years in China. It must work.

Note: It is also not reasonable to reject a claim solely because it is part of a tradition. Children have always be given few rights under the law. Its time to throw out oldfashioned ideas and bring in the new.

Appeal to Ignorance  In an appeal to ignorance one concludes that something is true just because it has never been proven false. - You can’t have evidence/ haven’t looked for evidence (doesn’t mean it’s true)  People have tried to prove the claims of astrology true, but have failed. Thus, the claims of astrology must be false.  People have tried to prove the claims of astrology false, but have failed. Thus, the claims of astrology must be true. My wife must be having an affair, because I can’t prove that she isn’t. My wife doesn’t keep a Winnebego in our garage, because I’ve never seen one there. (NOT an appeal to ignorance because you do know you’ve never seen one in your garage) Members of the jury, the prosecution has failed to prove my client guilty beyond a reasonable doubt. Therefore, he is not guilty.

Appeal to Emotion  The arguer attempts to support the conclusion by evoking emotion from the reader. I shouldn’t be found guilty because I have four children to support. There is no one to care for them if I go to jail. I shouldn’t be found guilty because I have a documented mental illness that causes me to make rash decisions. - Only a fallacy when strictly using emotion (no good reasoning)

Rhetoric is the artful use of non-argumentative language to persuade. If the passage contains reasons as well as emotion then it will not contain a fallacy. I lost my father to cancer. He started smoking when he was young and missed out on so many good years. If only he could have quit smoking. Smoking is deadly and addictive. We should enact laws to prohibit children from seeing advertisements for cigarettes.

Red Herring The Red Herring fallacy occurs when the arguer (often subtly) changes the topic of the argument but then claims that the original conclusion follows. - Distraction from the real issue There is a lot of talk about the need to eliminate pesticides from our vegetables. But vegetables are a necessary part of a healthy diet. So, we shouldn’t ban pesticides.

Straw Man  The Straw Man fallacy occurs when someone criticizes a position that was not originally held by the arguer. The argument has been either distorted, weakened or oversimplified. - Argument to cut down an argument that you made up which is similar to someone else’s argument (but worse/dumbed down) Atheists think that God does not exist, so everything is permitted. But even atheists must admit that I would not be permitted to kill them! So atheism is nonsense.  In the Straw Man fallacy one is distorting another’s argument and criticizing that.  In the Red Herring fallacy one is changing the subject, ignoring the first argument. In both a Straw Man and the Red Herring fallacy new premises are added to the argument. Examples Since he is a member of the National Rifle Association we shouldn’t believe what he says about animals rights.

Justice demands the death penalty for those that have murdered others. He killed our friend so now he must die! We are all here to see that justice is done.  People who want to ban dogs from running on beaches just want to ban dogs altogether. I have a right to own a dog so don’t listen to what they say.

Switzerland is 48 percent Protestant. Heidi is a Swiss. Therefore, Heidi is 48 percent Protestant.

Robert doesn’t know what he’s talking about. He’s mean-spirited and vulgar. Of course, he’d think children should not be able to play on the street.

All men are mortal. Therefore, some day man will disappear from the earth.

Jack should fail the course. He was too lazy to go to class, he didn’t study for the tests, and he isn’t a serious student, resulting in a poor performance.

If Thomas gives Marie a ring, then Thomas and Marie will be engaged. Thomas did give Marie a ring. In fact, he phoned her just the other night. Therefore, Thomas and Marie are engaged.

Victoria should enact a curfew for teenagers. Teenagers who spend quality time with their family do better in school and have healthy personal relationships.

The North American Free Trade Act is ruining the country. Just ask anyone working in manufacturing; they’ll tell you.

John is always late for meetings and he never finishes his reports on time. John is an irresponsible worker and a drain on the companies resources.

When asked whether or not they believe that a Green Party candidate should win in this riding, 75% of UVic students responded yes. Thus, the Green Party candidate must be the best person for the job.

No one has ever been able to prove the existence of extrasensory perception. We must therefore conclude that ESP is a myth.

The study found that 80 per cent of women who took the drug daily had no recurrence of breast cancer. But that doesn’t mean anything. The study was funded in part by the company that makes the drug.

Of course there is a God. Almost every civilization in history has believed in a deity of some kind.

Geraldo says that students who cheat on exams should not automatically be expelled from school. But it’s ridiculous to insist that students should never be punished for cheating.

Every player on the team is the best in the league. So the team itself is the best in the league.

Begging the Question  One can beg the question by using a premise that is essentially a restatement of the conclusion or providing a premise that is not known to be true independent of the conclusion. Abortion is murder, so abortion is wrong. Capital punishment is justified for the crime of kidnapping since it is legitimate that someone be put to death for such an inhuman act.  Also, one commits the fallacy of begging the question if one argues in a circle. General Motors clearly produces the finest cars in Canada. We know they produce the finest cars because they have the best design engineers. This is true because they can afford to pay them more than the other manufacturers. Obviously, they can afford to pay them more because they produce the finest cars in Canada. In all cases of begging the question, the arguer uses some linguistic device to create the illusion that inadequate premises provide adequate support for a conclusion. If no such attempt at illusion is made then there is no fallacy.

No dogs are cats. Thus, no cats are dogs. Valid and sound - Same sentence twice, no fallacy False Dilemma  A false dilemma occurs in an argument when one of the premises has an “or” statement but there are in fact more alternatives than the two presented in the disjunction. - Good form, bad content because the second option is unreasonable and there should be more options You should let me go to Anna’s after school or I will be miserable for the rest of my life. You don’t want me to be miserable for the rest of my life. So you should let me go to Anna’s. If you don’t let me go to Anna’s after school then I will be miserable for the rest of my life. You don’t want me to be miserable for the rest of my life. So you should let me go to Anna’s.  If one of the disjuncts is true then no fallacy is committed. Tofino is on Vancouver Island or it is on mainland BC. Tofino is not on mainland BC. Thus, Tofino is on Vancouver Island.

Slippery Slope  An argument commits the fallacy of the slippery slope when there is the assumption that a chain reaction of events will take place when it is not reasonable to assume so. Usually, the result of the argument is disaster. - Assumed that things are linked when they are not Genetic testing on embryos should be outlawed. If we start testing on embryos then we’ll do testing on fetuses and eventually we’ll be using children as guinea pigs. If you take that step off of the roof, you’ll fall ten feet down and then another ten feet down and eventually you’ll go splat on the cement sidewalk. - Not SS because it is reasonable to assume this will happen

If we allow Communism to thrive in Vietnam then Communism will spread to its neighbours and will soon infect the entire region. - Spacial slippery slope; countries’ political situations don’t necessarily spread to geographically close countries Hasty Generalization  A hasty generalization is a fallacy that occurs in inductive arguments when the sample used as evidence for the conclusion is not representative of the group.  For instance, the sample size may be too small or not randomly selected.  100 000 people from Calgary were asked what party they would vote for in the next election. 75% of them said they would vote Conservative. Therefore, the Conservatives will have a majority government.

 At the last three parties that I went to, I found the Figowitz beer flat and bitter. Probably, I would find every bottle of Figowitz beer flat and bitter. - NOT a fallacy because the beer should always taste the same/similar - Only talking about a personal opinion Careful! Composition may be confused with Hasty Generalization Fleas are small. (applies to each individual flea – general statement) Fleas are numerous. (applies to group of fleas) If the conclusion is general statement then fallacy is hasty generalization. If the conclusion is a claim about a class (group) of objects then the fallacy committed is composition. These bricks are small, so all of the bricks are small. (HG) These bricks are small, so the wall will be small. (Composition)

Faulty Analogy  In an inductive argument from analogy one uses the common features between two examples to conclude that they also share another feature.  The fallacy of faulty analogy occurs when the analogy made is not strong enough to support the conclusion.

 Bill’s new mountain bike has disk brakes, is blue in colour and was on sale. Chad’s new mountain bike has disk brakes and is blue in colour, so it must be on sale as well. - Properties they share don’t say whether or not it will be on sale, too vague - Fallacy  Bill’s mother taught him how to mountain bike and now he is good enough to win many of his races. Bill’s younger brother Chad was taught how to mountain bike by their mother as well. Thus, Chad is probably good enough to win his races. - Not a fallacy - Relevant between two cases: brothers (similar build), same coach

Examples Either we require forced sterilization of Third World peoples or world populations will explode and all of us will die. (false dilemma) People who lack humility have no sense of beauty because everyone who has a sense of beauty also has humility. (begging the question) The secretaries have asked us to provide lounge areas where they can spend their coffee breaks. This request will have to be refused. Next they’ll want spas and swimming pools and we will go bankrupt. (slippery slope) Tom and his brother Evan both like scuba diving. Therefore, it is likely that the rest of their family likes scuba diving as well. (hasty generalization; family is composed on individuals, not one group) Tom and Sue both run marathons and have arthritis in their knees. Therefore, anyone who starts running marathons can expect to get arthritis in his or her knees. (hasty generalization) Tom and Sue both run marathons and have arthritis in their knees. Therefore, if Cody starts running marathons, he too can expect to get arthritis in his knees. (faulty analogy: one person in conclusion) No one would buy a pair of shoes without trying them on. Why should anyone be expected to get married without premarital sex?

(Faulty analogy: not similar) Victoria should enact a curfew for teenagers. According to documents from the Victoria Police Department, 80% of thefts and acts of vandalism committed in Victoria are done by teenagers after 10pm.

On Friday I drank 10 rum and Cokes and woke up the next morning with a headache. On Saturday I drank 10 gin and Cokes and woke up the next morning with a headache. If I want to avoid waking up with a headache, I better give up drinking Coke. (Faulty analogy: picking out the irrelevant feature)...