lecture 8 - Faulty reasoning Logic and Reasoning PHIL 102[8...

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9/19/2011 1 Logic and Reasoning PHIL 102 [8] Sept 19 Chapter 5 Faulty reasoning In-class test 28 Sept (instead of lecture) Covers ch. 1 to ch. 5 Test preview on Sept 26 Faulty reasoning 2 Reasoning b argument b premises - irrelevant - unacceptable Know thy enemy - Recognize the fallacies when you see them - Avoid making these errors - More than one is possible - Some overlapping - More than what’s in the lecture notes and in the textbook b Arguing that a claim should be accepted or rejected based on its origin, not on its merits - “Dr Smith says that we should spend more state revenue on education. But Dr Smith is a professor who wants a better salary” genetic fallacy Irrelevant premises 1 Bad reasoning 5 b Attacking the source of an argument (the person) instead of the argument itself: - “Bill Clinton said marriage is important. But he cheated on his wife” - “The doctor said that smoking is bad for one's health; but he smokes too.” - “John said capital punishment is wrong. But he’s too old to think straight” argument against the person ( ad hominem ) (related to genetic fallacy) 5 Irrelevant premises 2 Bad reasoning 18 Every member of the team won the Stanley Cup; therefore the team won the Stanley Cup. b What is true about the whole might not be true about the parts (and vice versa) “This green desk is made up of smaller things called atoms. Since the desk is green, its atoms must be green too.” 6 fallacy of composition division Irrelevant premises 3
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9/19/2011 2 Bad reasoning 17 “I oppose taxes that hinder economic growth” (I oppose these taxes, that hinder growth, but I agree with other taxes, that don’t) (I oppose all taxes, because they hinder growth) “Last night I shot an elephant in my pajamas. How he got in my pajamas, I’ll never know.” (Groucho Marx) 7 semantic ambiguity Irrelevant premises 4 Bad reasoning 17 b Terms are used with different meanings “Only man is rational. No woman is a man.
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lecture 8 - Faulty reasoning Logic and Reasoning PHIL 102[8...

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