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Fallacies of Presumption, Ambiguity, and Grammatical Analogy

Fallacies of Presumption, Ambiguity, and Grammatical Analogy. Fallacies of Presumption Overview. Key characteristic: Premises presume what they claim to prove. Begging the Question: Definition.

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Fallacies of Presumption, Ambiguity, and Grammatical Analogy

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  1. Fallacies of Presumption, Ambiguity, and Grammatical Analogy

  2. Fallacies of PresumptionOverview • Key characteristic: Premises presume what they claim to prove.

  3. Begging the Question:Definition • Occurs when an arguer uses some form of phraseology to conceal a key premise that may be unsupported by argument

  4. Begging the Question:Examples • Murder is morally wrong. This being the case, it follows that abortion is morally wrong. • Comment: Ignores the fact that the argument doesn’t prove that abortion is murder, which is the real point of controversy.

  5. Complex Question:Definition • Occurs when a single question that is really two (or more) question is asked and a single answer is then applied to both questions

  6. Complex Question:Examples • Do you still beat your wife? • Comment: However you answer this question, it commits you to saying that you engaged in this behavior in the past. • Have you stopped cheating on exams? • Comment: Supposes that you have cheated in the past.

  7. False Dichotomy:Definition • Occurs when the arguer assumes there are only two alternatives when in fact there are more than two.

  8. False Dichotomy:Example • Either you buy only American-made products or you don’t deserve to be called a loyal America. Yesterday you bought a new Toyota. It’s clear you don’t deserve to be called a loyal American! • Comment: The person may still be a very loyal citizen.

  9. Suppressed Evidence:Definition • Ignores some important piece of evidence that: 1) outweighs the presented evidence 2) entails a very different conclusion. • Difficult to detect because you must know about the details of the case.

  10. Suppressed Evidence:Example • Used car salesman: “This car is a great value. It’s clean and has low mileage.” • Comment: The salesman may not be telling you that the car had been in a serious crash.

  11. Equivocation:Definition • Occurs when the conclusion of an argument depends on a word or phrase that is used (explicitly or implicitly) in two different senses. • Such arguments are either invalid or have a false premise.

  12. Equivocation:Example • Some triangles are obtuse. Whatever is obtuse is ignorant. So some triangles are ignorant. • Comment: “Obtuse” is used in two ways: • Greater than 90 degrees • Not smart

  13. Amphiboly:Definition • Occurs when the arguer misinterprets a statement that is syntactically or grammatically ambiguous • and then proceeds to draw a conclusion based on this faulty interpretation.

  14. Amphiboly:Example • 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. • Comment: The phrase “in the biology lecture hall” should be placed immediately after “lecture” instead of “heart failure.”

  15. Composition:Definition • This fallacy occurs when the conclusion of an argument depends on the erroneous transference of an attribute from the part of something to the whole.

  16. Composition:Example • Each sentence in this composition is well-written. Therefore the whole essay is well-written. • Comment: It doesn’t follow from the fact that each individual sentence is well written that the whole essay is well written.

  17. Division: Definition • Occurs when the conclusion of an argument depends on the erroneous transference of an attribute form a whole (or a class) onto its parts (or members).

  18. Division: Example • America is a wealthy country. Bill Smith is an American, therefore he is wealthy. • Comment: Even though it is true that the country as a whole is wealthy, it doesn’t follow that each individual in the country is a wealthy individual.

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