批判性思维第八章1.ppt

Chapter 8 How good is the evidence: intuition, personal experience, testimonials, and appeals to authority? by雷玲、孙杰 The Need For Evidence We encounter many conclusions , reasons, or assumptions, but we don’t know whether they are dependable. We need evidence to prove whether they are true or false. The greater the quality and quantity of evidence supporting a claim, the more we can depend on it, and the more we can call the claim a “fact”. How to determine dependability? These questions: What is your proof? Where is the evidence? Are you sure that’s true? How do you know that’s true? Why do you believe that? Can you prove it? Locating factual claims (P.105) We encounter factual claims as (a) descriptive conclusion, (b) reasons used to support either descriptive or prescriptive conclusion, or (c) descriptive assumption. Examples : Frequently use of headphones may cause hearing loss. recent crime statistics report an increase in the number of gun related crimes over the last 10 years. The monetary costs of switching to hybrid cars and alternative energy sources are far less than the political benefits to decreasing dependency on fossil fuel. Intuition as evidence When we use intuition to support a claim, we rely on “common sense”, or on “gut feelings”, or on hunches. A major problem with intuition is that it is private. We must be very wary of claims backed up only by intuition. Dangers of appealing to personal experience as evidence “I cross the street all the time without looking, and I have never been hit by a car. Therefore I do not see the need to look both ways before crossing.” Personal experience often lead us to commit the hasty generalization fallacy. Exceptions: When an experienced pilot has an intuition that the plane doesnt feel right as it taxis for takeoff. Sometimes such “hunches” are not blind. Pay attention to the following problems with testimonials: