Philosophy_110_Chp9[1]

Philosophy_110_Chp9[1] - Deductive Evaluation Review...

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4/3/2009 1 Chapter 9 Inductive Evaluation Deductive Evaluation: Review 8.6/28B: The act was the killing of a human being. Thus, that act was morally wrong. 1: Unknown Inference from 1 to 2: Invalid Argument as a whole: Unsound Problems with Deductive Evaluation 1. True/False does not show: The range of confidence we may have in statements So, for inductive arguments , we will evaluate premises on the basis of their “credibility” Is it “true” that evolution explains the diversity of life on Earth? No, but it is extremely credible. Was it “true” that, before the 2008 election, Barrack Obama would be President? No, but moderately credible. Was it “false” that, before the 2008 election, that Ralph Nader would not be President? No, but it was at least “moderately credible” that Nader would not win the Presidency. Inductive Evaluation of Premises Complete non-credible (0%) Example : All men are fish. Extremely non-credible (1%) Very non-credible (25%) …. Moderately credible (50%) Example: This coin will come up heads. Very credible (75%) Extremely credible (99%) Completely credible (100%) Example : Socrates is a man. Problem #2 w/ Deductive Evaluation 2. Validity does not show: STRENGTH of inferences Sometimes we can have an argument that establishes its conclusion with varying degrees of strength. Inductive Evaluation of Inferences Inferences will be evaluated as more or less strong . Ex: Bob is going to take a plane to Chicago tonight. Thus, Bob is going to die tonight. 1: Unknown Inference from 1 to 2: Extremely weak inference (1% confidence) Ex: I am going to take a plane to Chicago tonight. Thus, I will arrive safely in Chicago tonight. Extremely strong inference (99%+ confidence) Notice: this is NOT VALID (0%) Of no strength …Extremely Weak(1%) Moderately Strong(50%) … Extremely Strong… Valid (100%)
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4/3/2009 2 From 8.6/#16B Nixon is a white male. Kennedy is a white male. Clinton is a white male. I conclude that all U.S. Presidents have been white males. 1: Completely credible 2: Completely credible 3: Completely credible Inference from 1 & 2 & 3 to 4: Very weak inference. Argument as a whole: very unreasonable
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Philosophy_110_Chp9[1] - Deductive Evaluation Review...

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