Chapter 4. Credibility

Transcription

1 Chapter 4 Credibility

2 How believable is a claim? How credible is a source? 2

3 Not an all-or-nothing thing! Statements/sources vary in credibility. 3

4 For example: The teacher owns a duck. The teacher owns a dump truck. The teacher owns a hippopotamus. 4

5 Why is it harder to believe the teacher owns a hippopotamus? It raises more questions. How d she get one? Where does she keep the sucker? Say isn t it illegal to keep a hippo? Etc. 5

6 In short: The idea of the teacher owning a hippo conflicts with your background knowledge. 6

7 Royalty-Free/CORBIS 7

8 Believable is NOT entirely subjective: Mr. Zingg drinks a pint of sulfuric acid each night before bed. 8

9 Which is most UNBELIEVABLE? Teacher is under 20 years old. Teacher is under 55 year old. Teacher is under 90 years old. 9

10 Which is LEAST unbelievable? They ve taught crows how to play checkers. W. arranged 9/11 so he could invade Iraq and get its oil. Dr. Moore is related to George Washington. Bigfoot exists. We have been visited by space aliens. Some of them are taking this class. Which is MOST unbelievable? 10

11 Obviously: The more unbelievable the claim, the stronger the argument you need to accept it. 11

12 12 For example: Dean Stooler can run a mile in less than four minutes. Dean Stooler can run a mile in less than seven minutes. More is required to establish the first statement.

13 Watch out for things you accept just because you ve heard them so often: A critical thinker will want EVIDENCE before accepting what everyone knows. 13

14 Old wives tales? Daddy long legs are the world s most poisonous spider. Eating carrots makes you see better. Aspirin with Coca-Cola will make you drunk. Pop Rocks followed by Pepsi can make your stomach explode. Going outside with wet hair will give you a cold. (more ) 14

15 Old wives tales? Reading in dim light will hurt your eyes. Too much TV will hurt your eyes. Chocolate causes pimples. Coffee stunts your growth. Crossing your eyes can make you cross-eyed. Cracking your knuckles causes arthritis. 15

16 Credibility of Sources 16

17 Two kinds of doubt: 1. Doubts about a source s knowledge 2. Doubts about a source s truthfulness, objectivity, reliability 17

18 Smitty knows a lot, but you can t t trust a word he says. Smitty never lies, but he doesn t t know a thing. Either way, Smitty isn t the best source. 18

19 Q: Can you tell if a person (not someone you know) is lying to you? Are there any tell-tale clues? 19

20 Excessive sweating? Shifty eye movement/avoiding eye contact? Staring up to the left/other micro-expressions? Wimpy handshake? Changing the subject? Appearing lacking in self-confidence? Nervous laughter? 20

21 If any of these were at all reliable, we wouldn t t need courts, ID checks, lie detectors, blah blah blah Why would teachers take precautions against cheating, if they could just look at a kid and tell? 21

22 Need four volunteers! 22

23 A more scientific experiment: Need just two volunteers 23

24 Here are your voting options. T/T: Both telling truth L/L: Both lying T/L: First person truthful; second is lying L/T: First person lying; second is truthful 24

25 Even a truthful source can: Make MISTAKES Be BIASED LACK EXPERTISE 25

26 How to judge a person s expertise? 26

27 Self-confidence/nervousness? Clothes? Posture? Gender? Accent? Nationality? 27

28 Those all seem pretty unreliable. Anyone can LOOK like an authority 28

29 Height? stm 29

30 How would YOU make someone look like a scientist? Use a stereotype! White lab coat or poor-fitting suit Pocket protector Glasses; thick Gray hair German/British accent, etc. 30

31 Conclusion: It s s difficult to measure a person s s expertise by looking at him or her. 31

32 BEST indicators of a source s Education Experience Reputation Position knowledge are these: Achievements 32

33 Does being an expert in one field make you an expert in another field? Not if the two fields aren t related. An expert in economics doesn t automatically qualify as expert in, say, political science. An expert in oceanography shouldn t be assumed to be an expert in genetics. Your business prof can t be assumed to have expert knowledge of history. 33

34 A common mistake: To attach EXTRA authority to what someone says JUST because he/she: Is your parent Is your friend Is your teacher (Being a TEACHER carries extra weight in the person s field, but the fact he/she is YOUR teacher doesn t add anything.) 34

35 Other sources: Newspapers; other print media Electronic media; TV, radio The Internet is actually a source of sources, not a source in itself. University publications Government publications Professional journals 35

36 An example of an unreliable news source? The weekly rag available in the checkout line. REDNECK ALIENS TAKE OVER TRAILER PARK! 36

37 A much better source: The website of the Sacremento Bee 37

38 Even better (because more complete): The New York Times newspaper 38

39 One final idea 39

40 Sometimes you get an unbelievable claim coming from a credible source. Like, say, from a friend or a relative. 40

41 Like, I had an aunt who was convinced she saw a ghost. Good old Aunt Rose she had no reason to lie, and she was as honest as the day is long. 41

42 This brings us to Hume s principle. Hume? 42

43 David Hume Library of Congress David Hume ( ), a nice chap. Liked to play whist. Here s what he said 43

44 Hume s s principle: No testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous than the fact it endeavors to establish. 44

45 When anyone tells me he saw a dead man restored to life, I consider whether it be more probable that this person should either deceive or be deceived, or that the fact he relates should really have happened. I weigh the one miracle against the other; and always reject the greater miracle. If the falsehood of his testimony would be more miraculous than the event which he relates, then, and not till then, can he pretend to command my belief or opinion. 45