Informal Logic, Famous Fallacies - PowerPoint Presentation

Informal Logic, Famous Fallacies Don’t Be Fooled by Bad Arguments

First, what are arguments? Distinguish arguments from explanations: Arguments are the assertion of a conclusion from reasons that are better known than the conclusion.Explanations are the assertion of reasons for a conclusion that is better known than those reasons. Bill punched Bob in the nose. Bob is in pain. Warm, moist air hit a cold front. It is raining.

Classification of Fallacies Fallacies of Relevance: Appeal to Force Appeal to Pity Appeal to the PeopleAd HominemAccidentStraw man Missing the PointRed Herring Weak Induction:Appeal to Unqualified AuthorityAppeal to IgnoranceHasty GeneralizationFalse CauseSlippery SlopeWeak Analogy Fallacies of Presumption: Begging the QuestionComplex QuestionFaulty Dilemma Fallacies of Ambiguity: Equivocation Amphibole Fallacies of Grammatical Analogy: Composition Division

8 Fallacies of Relevance* 1. Appeal to Force (ad Baculum … appeal to the stick): Supporting or avoiding a conclusion by threats Worst case: when debates get derailed by jeering or “shouting down” an arguer. “I think we should choose xBox over Playstation because its online multiplayer stuff is better.”“How about I stomp your guts out? How would that be?” Committing Appeal to Force is less an error in reasoning, more a bullying tactic. Either way, the response is irrelevant to the quality of the argument or idea.

Fallacies of Relevance, cont. 2. Appeal to Pity (Argumentum ad Misericordiam): “I’m afraid going 70 in a 25mph zone means you deserve this ticket, Ms. Garcia.” “No, Judge, I have three kids, late bills, and work two jobs … I can’t deserve this speeding ticket!”Is the sorry state of the arguer logically relevant to deserving the ticket? Might the judge considering it in sentencing?

Fallacies of Relevance, cont. 3. Appeal to the People (Argumentum ad Populum): Ad Populum has the form: X is popular X is trueDirect Approach: appeal directly to the crowd of people … use emotive language to create mob mentality support for a conclusion. Political speeches? Twitchfork mob incitement?Indirect Approach : appeal indirectly to the crowd by appealing directly to individuals and their relationship to the crowd … sometimes called a “Bandwagon Argument”: “Come on … everyone in this class smokes crack ... you should take a hit!”Individual crowd

Fallacies of Relevance, cont. 4. Argument to the Person (Argumentum ad Hominem): Attacking the arguer instead of their argument. Famous response to an ad hominem attack: “I may be the devil’s brother, but you still haven’t answered my argument.”3 Kinds of ad Hominem arguments:Abusive ad Hominem :“I believe murderers should die for the sake of their victim’s family.”“Only a stupid jerk-face would want anyone to die!”…does the speaker being a jerk have anything to do with whether capital punishment is justified based on concern for the victim’s family?

Fallacies of Relevance, cont. Circumstantial ad Hominem : “I believe murderers should die for the sake of the victim’s family.” “Well, since your cousin was murdered, it isn’t hard to see why you feel that way.”Tu Quoque (you too): “I believe murderers should die for the sake of the victim’s family.” “Well, I recall you defending your Uncle when he was convicted … you weren’t suggesting he die for the family of the guy he shot!”

Fallacies of Relevance, cont. 5. Accident: (Misapplying a Rule): “Yes I told the axe murderer where the little girl was! … if you check your bible, you’ll find Thou Shalt Not Lie ”

Fallacies of Relevance, cont. 6. Straw Man (Straw Position ):Famous quote: “If the defendant be a man of straw, who is to pay the penalty?”Distorting your opponent’s view or position by exaggerating or diminishing it, then attacking the distorted position rather than the one the opponent holds. Universal health care?! Well that’s just plain, old-fashioned Communism! (exaggeration)Intelligent Design? Well, that’s just plain old churchy creationism! (diminishment)

Fallacies of Relevance, cont. 7. Missing the Point: “So, you say Bill punched Bob in the nose? All right, better get Bob straight to the emergency room!” Sometimes MtP is jumping to a distant conclusion.Sometimes MtP is just missing the point.“That’s a priceless Steinway!” “Not anymore.” http://www.youtube.com/watch?v=LwtIKdCWXls“If you’re not out of here in 5 seconds…!” “Ah, I could easily be out of here in three!”

Fallacies of Relevance, cont. 8. Red Herring: Leading listeners off track with a related, enticing or distracting line of thought. “I don’t think God exists. To me, there’s just too much evil in the world to believe that.” “Ah. Yes, evil is bad. But the best way to handle it, if it upsets you, is to seek out a therapist, or perhaps pastoral care. Therapy has been shown to work wonders; I don’t see why you would avoid it … see you in church!”

Quick Quiz: We should give that new position to Frank Thompson. Frank has six hungry kids to feed, and his wife needs an operation to save her eyesight. AF = Appeal to Force APi = Appeal to Pity Ape = Appeal to the People aH = ad Hominem A = AccidentSM = Straw ManMP = Missing the PointRH = Red Herring NF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: Professor Pearson’s arguments in favor of the theory of evolution should be discounted. Pearson is a cocaine-snorting sex pervert and, according to some reports, a member of the communist party. AF = Appeal to Force APi = Appeal to Pity Ape = Appeal to the People aH = ad Hominem A = AccidentSM = Straw ManMP = Missing the PointRH = Red Herring NF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: Some of you oppose the appointment of David Cole as new sales manager. Upon further consideration, I am sure you will find him suitable for the job. If not confirmed, it may be necessary to make severe personnel cutbacks in your department. AF = Appeal to Force APi = Appeal to Pity Ape = Appeal to the People aH = ad Hominem A = AccidentSM = Straw ManMP = Missing the PointRH = Red Herring NF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: You should read Irving Stone’s latest novel right away. It has sold over a million copies, and nearly everyone in the Manhattan cocktail circuit is talking about it. AF = Appeal to Force APi = Appeal to Pity Ape = Appeal to the People aH = ad Hominem A = AccidentSM = Straw ManMP = Missing the PointRH = Red Herring NF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: Animal rights activists say that animals are abused in biomedical research labs. But consider this: Pets are abused by their owners every day. Probably 25 percent of pet owners should never get near animals. Some cases of abuse are enough to make you sick! AF = Appeal to Force APi = Appeal to Pity Ape = Appeal to the People aH = ad Hominem A = AccidentSM = Straw ManMP = Missing the PointRH = Red Herring NF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: Actress Andie MacDowell says that it’s healthy to drink milk. But the dairy industry pays MacDowell thousands of dollars to make these ads. Therefore, we shouldn’t take her testimonials too seriously. AF = Appeal to Force APi = Appeal to Pity Ape = Appeal to the People aH = ad Hominem A = AccidentSM = Straw ManMP = Missing the PointRH = Red Herring NF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: Dr. Morrison has argued that smoking is responsible for the majority of health problems in this country and that every smoker concerned about his or her health should quit. Unfortunately, however, we must consign Dr. Morrison’s argument to the trash bin. Only yesterday I saw none other than Dr. Morrison himself smoking a cigar. AF = Appeal to Force APi = Appeal to Pity Ape = Appeal to the People aH = ad Hominem A = AccidentSM = Straw ManMP = Missing the PointRH = Red Herring NF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Fallacies of Weak Induction 9. Appeal to Unqualified Authority (ad Verecundiam): “My Econ professor said to never scold my dog, so, now I’m a 100% positive feedback dog trainer.” A PhD in Economics doesn’t imply dog training skill.2 things: Perhaps the Econ professor is a dog training expert … but that has to be shown. In some areas, no one is an expert: famously, politics, morals, and religion

Fallacies of Weak Induction, cont. 10. Appeal to Ignorance (ad Ignorantiam): Arguing from a lack of knowledge: No one has proven X true , (or false)X is false (or true)As in… “No one has proven God exists.”“Is that so?”“Yes! So, God does not exist!”“No one as proven God doesn’t exist.”“Is that so?”“Yes! So, God exists!”

Fallacies of Weak Induction, cont. Appeal to Ignorance, cont. Exceptions (below are good arguments (pretty good)): “Guy’s innocent.” “Says who?”“Well, he hasn’t been proven guilty, so he is innocent.” “There is no crocodile in the hall.”“Says who?”“Well, no one has proven there’s a crocodile in the hall, so there isn’t.”

Fallacies of Weak Induction, cont. 11. Hasty Generalization (Converse Accident): Taking a small sample, and inferring from it all or most of that kind are the same. “My cabbie in New York City was surly, so, all cabbies in NYC are surly.” Exceptions:“This Root Beer, Roundy’s, is blah, so all Roundy’s Root Beer is blah.” “This Pit Bull (Rottweiler, Tarantula, Python, etc.) is dangerous, so, all Pit Bulls (Rottweilers, Tarantulas, Pythons, etc.) are dangerous.”

Fallacies of Weak Induction, cont. Two more things regarding the logic of danger (#2): When people say Pit Bulls, for instance, are dangerous, they plainly don’t mean to include dead ones, very old ones, very young ones. Their statement is perhaps elliptical for, “these healthy adult dogs can kill you and animals are unpredictable. Be on guard!” You must decide if a statement is straight-forward or elliptical based on context, knowledge of the speaker, or by asking, if possible. Risk assessment logic: Risk assessments have 2 parts: probability and, severity. Some things have very low probabilities of harm, but are dangerous because of high severity. Commonly believed dangerous things: your weird looking neighbor, flying in a commercial jet, driving a car without a seatbelt, playing just one round of Russian Roulette, hitchhiking. All have very low probabilities of harm. How then are they dangerous?

Fallacies of Weak Induction, cont. 12. False Cause (3 Kinds) 1. False Cause: Post Hoc : Post hoc, ergo, propter hocAfter this, therefore, because of this “Ever since Betty showed up it’s been one thing after the other, car breaks down, dog dies, TV on the fritz! Clearly, Betty is bad news!”“Right about the time Obama took office the economy really took a dive. I guess we know that guy is bad for business!”“While Reagan was taking office Iran freed the hostages. Plain to see he knew how to take care of business!” Post Hoc

Fallacies of Weak Induction, cont. 2. False Cause: Mere Contributive Cause (oversimplified cause) A Contributive Cause: one cause that is insufficient, by itself, to produce the effect in question, but that contributes to producing the effect. “Edgar hung himself while listening to Suicide Solution by Ozzy Osbourne … Ozzy should go to jail for causing his suicide.”How might you, as a defense attorney, using the notion of a contributive cause, argue that this conclusion is fallacious?

Fallacies of Weak Induction, cont. 3. False Cause: Confused Causal Chains Suppose we conclude that a dog was barking because someone broke into its house: an intruder (X) caused the dog to bark (Y), X caused Y … couldn’t it be … Y caused X (someone intruded because the dog was barking)? Y caused a fire Z, which caused X (dog barking caused someone to start a fire, and the fire made someone break into the house)?X had nothing to do with Y (the dog was barking at a mouse; intruder broke in to steal a TV)?Others?

Fallacies of Weak Induction, cont. 13. Slippery Slope: “If we allow gay marriage, how do we keep from allowing polygamy, and then polyamory, then sibling and parent marriage, thenpet marriage? We will slide down the slope into chaos!”Show the slope really is slippery: historystatisticsmotives

Fallacies of Weak Induction, cont. Slippery Slope, cont. Throwing sand on a slippery slope : Cite the differences between the case at hand the next step in the slope, or at each step … try to show, for instance, that jealousy makes polygamous marriages unstable, or that rich men getting 20 wives harms society by shrinking the family opportunities of poor men … so, we surely won’t slide down the slope?

Fallacies of Weak Induction, cont. 14. Weak Analogy: A has a, b, c, and z B has a, b, c So, B probably has z. (this is the form of an analogy, not a weak analogy) National 65 mph speed limit kills 42,000 US citizens per year, and no one minds much.The war in Iraq kills 1,000 US soldiers a yearSo, no one should mind that much either. A B a a z z

Fallacies of Weak Induction, cont. To evaluate the analogy, we have to compare every relevant feature we can think of between the national speed limit and the war in Iraq, and see if those features strengthen or weaken the analogy. Are both government policies? Do they serve worthy goals? Do the policies put each group at equal risk? Does risk matter, or just total lives lost?Can society survive without either policy?Can those endangered opt out of the policy’s purview? Who are the relevant dead of each policy?Are injuries equally bad?So on…

Quick Quiz: If you give Jane a cookie, she’ll want a glass of milk. Then, she won’t be hungry for her supper! AUA = Appeal to Authority AI = Appeal to Ignorance HG = Hasty Generalization FC = False Cause SS = Slippery SlopeWA = Weak AnalogyNF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: Don’t listen to Rush Limbaugh. After Bob started listening, he developed an ulcer. AUA = Appeal to Authority AI = Appeal to Ignorance HG = Hasty Generalization FC = False Cause SS = Slippery SlopeWA = Weak AnalogyNF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: Ellen is a mean drunk. I wouldn’t invite her to your kegger, if I were you. AUA = Appeal to Authority AI = Appeal to Ignorance HG = Hasty Generalization FC = False Cause SS = Slippery SlopeWA = Weak AnalogyNF = No Fallacy

Quick Quiz: No one would buy a pair of shoes without trying them on. Why should anyone be expected to get married without first having sex? AUA = Appeal to Authority AI = Appeal to Ignorance HG = Hasty Generalization FC = False Cause SS = Slippery SlopeWA = Weak AnalogyNF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: There are more churches in New York City than in any other city in the nation, and more crimes committed in New York City than anywhere else. So, if we are to eliminate crime, we must abolish churches. AUA = Appeal to Authority AI = Appeal to Ignorance HG = Hasty Generalization FC = False Cause SS = Slippery SlopeWA = Weak AnalogyNF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: Probably no life exists on Venus. Teams of scientists have conducted exhaustive studies on the planet’s surface and atmosphere, and no living organisms have been found. AUA = Appeal to Authority AI = Appeal to Ignorance HG = Hasty Generalization FC = False Cause SS = Slippery SlopeWA = Weak AnalogyNF = No Fallacy *from Hurley’s A Concise Introduction to Logic

Quick Quiz: We don’t dare let animal rights activists get their foot in the door. If they sell us on the idea that dogs, cats, and dolphins have rights, next it will be chickens and cows. Next, it will be worms and insects. This will lead to the decimation of our agricultural industry. The starvation of the human race will follow close behind. AUA = Appeal to Authority AI = Appeal to Ignorance HG = Hasty Generalization FC = False Cause SS = Slippery SlopeWA = Weak AnalogyNF = No Fallacy *from Hurley’s A Concise Introduction to Logic