chapter 4: informal fallacies © oxford university press

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Chapter 4: Informal Fallacies Oxford University Press Slide 2 In This Chapter A.Fallacies of Relevance B.Fallacies of Unwarranted Assumption C.Fallacies of Ambiguity or Diversion D.Recognizing Fallacies in Ordinary Language Oxford University Press Slide 3 Fallacies of Ambiguity or Diversion A fallacy that occurs when the meanings of terms or phrases are changed (intentionally or unintentionally) within the argument, or when our attention is purposely (or accidentally) diverted from the issue at hand. 21.Equivocation 22.Amphiboly 23.Composition 24.Division 25.Emphasis 26.Straw Man Fallacy 27.Red Herring Fallacy Oxford University Press Slide 4 Equivocation Oxford University Press The intentional or unintentional use of different meanings of words or phrases in an argument. My older brother tries hard to be cool. I told him he has the personality of a cucumber. Since a refrigerator is a good place to keep things cool, he should spend some time there. Equivocation on cool: different meanings require the context of particular sentences for clarity. Slide 5 Examples: Some triangles are obtuse. Whatever is obtuse is ignorant. Therefore, some triangles are ignorant. Any law can be repealed by the legislative authority. But the law of gravity is a law. Therefore, the law of gravity can be repealed by legislative authority. A mouse is an animal. Therefore, a large mouse is a large animal. We have a duty to do what is right. We have a right to speak out in defense of the innocent. Therefore have a duty to speak out in defense of the innocent. Oxford University Press Slide 6 Amphiboly Ambiguity that arises when a poorly constructed statement muddles the intended meaning. He was shot in the train in the back in the sleeping car. (Was he shot in back or in the back of the train?) She watched the monkey eating a banana. (Who was eating the banana?) -- Sipping on a cup of cold coffee, the corpse lay in front of the tired detective. -- Cursing his bad luck, the DVD player refused to work for Eddie. Oxford University Press Slide 7 The amphiboly comes when the listener draws a probably mistaken conclusion from the ambiguous statement. Concluding that the corpse was enjoying the coffee, for example, would be an amphiboly. Examples: The tour guide said that standing in Greenwich Village, the Empire State Building could easily be seen. It follows that the Empire State Building is in Greenwich Village. John told Henry that he had made a mistake. It follows that John has at least the courage to admit his own mistakes. Professor Johnson said that he will give a lecture about heart failure in the biology lecture hall. It must be the case that a number of heart failures have occurred there recently. Oxford University Press Slide 8 Amphiboly can cause serious problems for contracts and wills. Consider: Mrs. Hart said in her will, I will leave my 500-carat diamond necklace and my pet ferret to Alice and Theresa. Therefore, we conclude that Alice gets the necklace and Theresa gets the ferret. Mr. James signed a contract that reads, In exchange for painting my house, I promise to pay David $5000 and give him my new Cadillac only if he finished the job by May 1. Therefore, since David did not finish until May 10, it follows that he gets neither the $5000 nor the Cadillac. Note: Equivocation is always traced to an ambiguity in the meaning of a word or phrase. Amphiboly involves a syntactical ambiguity in a statement. The Great Western Cookbook recommends that we serve the oysters when thoroughly stewed. Apparently the delicate flavor is enhanced by the intoxicated condition of the diners. Oxford University Press Slide 9 Composition Is committed when the conclusion of an argument depends on the erroneous transfer of an attribute from the parts of something onto the whole. All the cells in his body are tiny. Thus, he is tiny. The bricks in this building are sturdy, so the building must be sturdy. Compare: Every thread of material of which this shirt is composed is red, so the shirt is red. (Not a fallacy) Oxford University Press Slide 10 Other examples: Maria likes anchovies. She also likes chocolate ice cream. Therefore, she would like a chocolate sundae topped with anchovies. Each player on this basketball team is an excellent athlete. Therefore the team as a whole is excellent. Each atom in this teacup is invisible. Therefore, this teacup is invisible. Sodium and chlorine, the atomic components of salt, are both deadly poisons. Therefore, salt is a deadly poison. Compare: Every atom in this teacup has mass. Therefore, this teacup has mass. Oxford University Press Slide 11 Division The reverse of composition: this is when the conclusion of an argument depends on the erroneous transfer of an attribute from whole onto its parts. He is huge, so he must have huge cells. The cake tastes burnt, so you must have used burnt ingredients. Compare: That is a wooden chair, so the legs are made of wood. (Not a fallacy) Oxford University Press Slide 12 Other examples: Salt is a nonpoisonous compound. Therefore, its component elements, sodium and chlorine, are nonpoisonous. The jigsaw puzzle, when assembled is circular in shape. Therefore, each piece is circular in shape. The Royal Society is over 300 years old. Professor Thomson is a member of the Royal Society Therefore, Professor Thomson is over 300 years old. Compare: This teacup has mass. Therefore, the atoms that compose this teacup have mass. This field of poppies is uniformly orange. Therefore, the individual poppies are orange. Oxford University Press Slide 13 Composition, Division, Hasty Generalization, and Accident First, determine whether the argument moves from particular to general or from general to particular. If the argument moves from part/specific to whole/general, then the appropriate fallacy is either that of composition or of hasty generalization. The fallacy of composition always moves from part to whole, while hasty generalization moves from specific to general. Then, to determine which fallacy applies, look at the conclusion. If the conclusion is a general (or distributive) statement, that is, if the attribute in question is being said to be true of each and every member of the class, then the fallacy is hasty generalization. If the statement is about the whole (class or collective), that is, if the attribute is said to be true collectively of a class as a whole, then the fallacy is composition. example: Each player on the basketball team is an excellent athlete. Therefore, the team as a whole is excellent. The above example commits the fallacy of composition. The conclusion does not point to each and every player, but rather to the team/class as a whole. Oxford University Press Slide 14 example: My brother's Ford threw a rod after only 25,000 miles. My cousin's Ford dropped its transmission when it was only six months old. Therefore, the Ford Motor Company only makes cars that are piles of junk. This example is a hasty generalization, as the conclusion is making the claim that each and every car made by the Ford Motor Company is a piece of junk. For this to fit the model for the fallacy of composition, the claim would have to be that the Ford Motor Company itself is a piece of junk. If, on the other hand the argument moves from the general/whole to the specific/part, then the applicable fallacy will either be that of accident or division. Division always moves from whole to part while accident moves from general rule to specific case. To determine whether the fallacy is division or accident, begin by looking at the premises. If the premises contain a general statement, then the fallacy is accident. That is, if what the premise asserts can be said of each and every member of the class, the appropriate fallacy is accident. If, on the other hand, the premise contains a class statement, then the fallacy is division. That is, if what the premise asserts can only be said of the class as a whole (that is, if it wouldn't make sense to apply it to all of the individual members of the class), then the fallacy is division. Oxford University Press Slide 15 example: Freedom of speech is guaranteed by the U.S. Constitution. Therefore, Joe should not be punished for yelling "Fire" last night in the crowded theater. The relevant fallacy in the above argument is accident, as the right to free speech mentioned in the premise is applicable to each and every individual who falls under the protection of the constitution. example: The average American family has 2.5 children. The Jones family is an average American family. Therefore, the Jones family has 2.5 children. This argument commits the fallacy of division as having 2.5 children cannot be said of each and every American family. (Have you ever seen half a child?) Rather, the statement is one that is only applicable to the class as a whole, and not to each of the individual members. Oxford University Press Slide 16 Emphasis Occurs when attention is purposely (or accidentally) diverted from the issue at hand. Jenn: He did win an Academy Award for best actor. Jess: You might think he did, but youre wrong. Jenn: I dont think, I know. Jess: I dont think you know either. Jess twists the meaning of a key phrase by changing the emphasis of Jenns claim (I dont think, I know), thus refuting Jenns claim of knowledge (I dont think you know). Oxford University Press Slide 17 Straw Man Fallacy Occurs when someones argument is distorted for the purpose of more easily attacking it, and then concluding that the opponents real argument has been demolished (a straw man is easily knocked down). Opponents position: She is against the new law that mandates teaching intelligent design alongside the theory of evolution. The distortion: It should be obvious to anyone that she really wants to eliminate religious beliefs. She wants us to destroy one of the basics principles of the Constitution of the Uni


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