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Chapter 30: Fallacies of Presumption

Chapter 30: Fallacies of Presumption. Begging the Question (pp. 349-351). Fallacies of presumption either assume what is to be proved or incorrectly assume that all the relevant information has been given.

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Chapter 30: Fallacies of Presumption

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  1. Chapter 30:Fallacies of Presumption

  2. Begging the Question (pp. 349-351) • Fallacies of presumption either assume what is to be proved or incorrectly assume that all the relevant information has been given. • All cases of begging the question are valid deductive arguments, since every statement entails itself.

  3. Begging the Question (pp. 349-351) • Assuming the conclusion as a premise • If you assume the conclusion you set out to prove as a premise, often stated in different words, the argument begs the question. Since the premises are to provide reasons to accept the conclusion, you’ve done so, but there is no more reason to accept the conclusion than there was to accept the premises: “I didn’t steal, since I didn’t take anything that wasn’t mine.”

  4. Begging the Question (pp. 349-351) • Arguing in a circle • If there are several arguments and the conclusion of the last is a premise of the first, there is a circular argument: Question: If you could live forever, would you and why? Answer: "I would not live forever, because we should not live forever, because if we were supposed to live forever, then we would live forever, but we cannot live forever, which is why I would not live forever."

  5. Begging the Question (pp. 349-351) • Question-begging epithets • An epithet is an adjective, noun, or phrase used to characterize a person or thing. • If one characterizes a person or thing with an epithet that corresponds to the issue at hand, one has begged the question: “All the evidence we have examined shows that that liar Biggs is guilty of perjury.” (Perjury is lying under oath.)

  6. Complex Question (pp.351-352) • Sometimes when we ask one question, we assume that another question has been answered. • Asking a complex question as such does not constitute an argument, and it is therefore not a fallacy. • Often the assumption is made that there is an implicit argument, particularly when the answer to the assumed question is incriminating.

  7. Complex Question (pp.351-352) • It’s a fallacy only if it is part of an argument. • In this case, the complex question provides the basis for an argument, as shown: Instructor: When did you stop cheating in this course? Student: On January 29. Instructor: Ah ha! So you admit you were cheating in this course. I shall need to bring this up before the Honor Council.

  8. Complex Question (pp.351-352) • Some complex questions do not provide the basis for fallacious reasoning. • You’re in court, and an attorney asks you, “Where were you on the evening of June 27, 2003?” This assumes that you were somewhere on the evening of June 27, 2003, but if you’re old enough to understand the question, you were somewhere on that evening. • Many questions we are asked are complex. It is reasonable to claim that there is a fallacy of complex question, and therefore an implicit argument, only if the question assumed to be answered is incriminating or open. “When did David write the 23rd Psalm?” assumes that the David of biblical fame wrote it, which is an open question.

  9. Suppressed Evidence (pp. 352-363) • When we develop an argument for a position, we generally do not provide all the evidence on both (or however many) sides of an issue. • The fallacy of suppressed evidence is committed when someone knowingly withholds relevant evidence: • Mr. Bigg, CEO of Bigg Enterprises, is presenting an argument at a town meeting that the town should allow him to build a new factory. He has stressed the economic advantages to the community. If he failed to mention in other communities where he has built factories the crime rate rose markedly, air pollution levels were seriously increased, etc., Mr. Bigg would be guilty of the fallacy of suppressed evidence.

  10. False Dichotomy (pp. 353-354) • A false dichotomy is a disjunctive syllogism with a false disjunctive premise: Either Diana is a Socialist or a Communist. She’s not a Socialist. So, she’s a Communist. If Diana were a Republican, then the disjunctive premise would be false, and the argument would commit the fallacy of false dichotomy.

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