1. Chapter 28: Fallacies of Ambiguity

2. Introduction to Informal Fallacies (pp. 319-320) A fallacy is an unacceptable argument. If there is no argument, there is no fallacy. A formal fallacy is an invalid argument. An informal fallacy is a common argumentative error. Often it is a valid argument with a false premise. The fallacies of ambiguity can be seen as formal fallacies: there is always a shift in the meaning of a word or phrase in the argument.

3. Equivocation (pp. 320-321) To equivocate means, literally, to speak in more than one voice. Equivocations outside of arguments –There are equivocations outside of arguments, but they’re not fallacies since there is no argument. Consider the following exchange from Through the Looking-Glass (Chapter 7): [Speaking of his messengers, the Red King says:] Just look along the road, and tell me if you can see either of them. “I see nobody on the road,” said Alice.

4. Equivocation (pp. 320-321) “I only with I had such eyes,” the King remarked in a fretful tone. “To be able to see Nobody! And at that distance too! Why, it’s as much as I can do to see real people, by this light!” –Since Alice uses ‘nobody’ as a pronoun and the King uses ‘Nobody’ as a proper name, there is an equivocation. Since there is no argument, there is no fallacy. The fallacy of equivocation –If there is a shift in meaning in the context of an argument, there is a fallacy of equivocation.

5. Equivocation (pp. 320-321) –We have already noticed this when discussing categorical syllogisms: if there is an equivocation in what appears to be a categorical syllogism there are four (or more terms), so it’s not a categorical syllogism. –Consider the following passage from Through the Looking-Glass (Chapter 7), in which the King talks with a messenger who had just arrived: “Who did you pass on the road?” the King went on, holding out his hand to the Messenger for some more hay.

6. Equivocation (pp. 320-321) “Nobody,” said the Messenger. “Quite right,” said the King, “this young lady saw him too. So of course Nobody walks slower than you.” “I do my best,” the Messenger said in a sullen tone. “I’m sure nobody walks much faster than I do!” “He can’t to that,” said the King, “or else he’d have been here first.” Here there is an argument, so there is a fallacy.

7. Amphiboly (p. 322) The fallacy of amphiboly occurs when there is a shift in meaning in the course of an argument due to loose sentence construction, and accepting the conclusion requires that the shift in meaning is unacknowledged. Poor sentence construction can result in ambiguous claims, as in “For those of you who have children and don’t know it, we have a nursery downstairs.” But in this case, there is no argument, so there’s no fallacy.

8. Amphiboly (p. 322) The following is an instance of the fallacy of amphiboly: “If you want to avoid cancer, you’ll want to avoid the Biology Building, since there is a lecture tonight on the causes of cancer in the Biology Building.” Presumably, the lecture is on the causes of cancer, and the lecture will be given in the Biology Building, but that’s not clear from the sentence construction. The conclusion requires that the causes of cancer — although, perhaps, not the lecture — are in the Biology Building.

9. Accent (pp. 322-324) There are two versions of this fallacy. A. Arguments based on unusual stress –If words in a common claim are given an unusual stress, the meaning can shift. If I argue, “The commandment says ‘Thou shalt not steal,’ so it’s okay for me to pilfer” I have committed the fallacy of accent.

10. Accent (pp. 322-324) B. Arguments based on incomplete quotations or quotations out of context –This is the more common form of the fallacy. It occurs when a quotation is taken out of context or is incomplete, and this shift changes the meaning of the claim. If I argue, “The commandment says ‘Thou shalt … steal,’ so it’s okay for me to pilfer, indeed it’s divinely commanded,” I have committed the fallacy of accent.

11. Division (pp. 324-325) A. Fallacy of division –The fallacy of division occurs when a property that is true of a whole thing or a whole class is improperly attributed to either a part of the whole or a member of the class. –If I argue, “My car is red. So, the tires on my car are red” I have committed the fallacy of division.

12. Division (pp. 324-325) B. Nonfallacious cases of division –It’s not always fallacious to attribute a property of a whole to a part. If I argue, “My car weights fewer than 3,000 pounds. So, the engine of my car weighs fewer than 3,000 pounds” there is no fallacy.

13. Composition (pp. 235-326) A. Fallacy of composition –The fallacy of composition occurs when a property that is true of a part of a whole or a member of a class is attributed to the whole thing or class. –If I argue, “The tires on my car are black. So, my car is black” I have committed the fallacy of composition: there is no connection between the color of the tires and the color of the car as a whole.

14. Composition (pp. 235-326) B. Nonfallacious cases of composition –There are cases in which the inference from a part to a whole is nonfallacious. If I argue, “The engine of my car weighs over 100 pounds, so my car weighs over 100 pounds” there is no fallacy.

15. Composition (pp. 235-326) –If I argue, “Wagner Hall was built after the college was founded, and Wagner Hall is over 100 years old. So the college is over 100 years old” there is no fallacy. But if you had less information, you wouldn’t know. If I argued, “Wagner Hall is over 100 years old. So the college is over 100 years old” you cannot know whether or not the inference is warranted. If Wagner Hall was built after the college was founded, the inference is a warranted. If the college was built on the site of a former plantation and Wagner Hall was formerly Mr. Wagner’s palatial home, the inference would not be warranted.

16. Fallacies of Ambiguity (pp. 320-326) Warning: In subsequent chapters we shall examine fallacies called Accident (Chapter 29) and Hasty Generalization (Chapter 31). Both of these concern principles or general statements. Many students confuse them with division and composition. In the case of division and composition, you are concerned with the relationship between parts and wholes (members of a class are “parts” of a class). In the case of Accident and Hasty Generalization, you are concerned with general statements. Do not confuse the two issues.