Section 7.3 What Do You Know?

1. Section 7.3What Do You Know? Knowing What Knowledge Is

2. Traditional Analysis of Knowledge • Knowledge is justified true belief. • S knows a proposition P if and only if: • P is true, • S believes that P is true, and • S is justified in believing that P is true.

3. Thought Experiment: Gettier’s Job Seekers • Suppose that Smith has strong evidence for the claim that Jones will get a job and that Jones has 10 coins in his pocket. • So he concludes (e) that the man who will get the job has 10 coins in his pocket. • It turns out, however, that Smith gets the job and has 10 coins in is pocket. • Even though Smith is justified in believing (e), he doesn’t know (e).

4. Gettier’s Guy in Barcelona • Suppose that Smith has strong evidence for the claim that Jones owns a Ford but doesn’t know where his friend Brown is. • So he concludes that (h) Either Jones owns a Ford or Brown is in Barcelona. • It turns out that Jones does not own a Ford, but Brown is in Barcelona. • Even though Smith is justified in believing (h), he doesn’t know (h).

5. The Defeasibility Theory • Diagnosis of the Gettier problem: there is additional evidence which, if known, would defeat the knowledge claim. • According to the defeasibility theory, knowledge is undefeated justified true belief.

6. Thought Experiment: Lehrer and Paxson’s Demented Mrs. Grabit • Suppose Lehrer sees someone who looks exactly like Tom Grabit steal a book from the library. • Mrs. Grabit, however, testifies that it was his twin brother John who stole the book. • This piece of evidence defeats your claim (d) that Tom stole the book. • But unbeknownst to you, Mrs. Grabit is a compulsive liar. So you do know (d) despite the defeaters.

7. The Causal Theory • Diagnosis of the Gettier problem: what makes the claim true is not what caused the person to believe it. • According to the causal theory, knowledge is suitably caused true belief.

8. Thought Experiment: Goldman’s Fake Barns • Suppose that Henry is driving through the countryside and points out to his son “That’s a barn.” • Suppose it is a barn, but suppose further that there are a number of fake barns in the area. • Even though the son’s belief that the object is a barn is caused by a real barn, he doesn’t know that it is.

9. The Reliability Theory • Diagnosis of the Gettier problem: the beliefs were not produced by reliable means. • According to the reliability theory, knowledge is reliably produced true belief.

10. Thought Experiment: Lehrer’s Human Thermometer • Suppose Mr. Truetemp has a thermometer implanted in his skull that causes him to have reliable beliefs about the temperature. • Suppose further that Mr. Truetemp never checks his temperature beliefs. • Even though his beliefs are reliably produced, he doesn’t have knowledge of the temperature.

11. The Explanationist Theory • Diagnosis of the Gettier problem: there are true propositions that contravene the knowledge claims. • According to the explanationist theory, knowledge is justified true belief that is truth resistant; that remains justified when all the evidence is taken into account. Such belief provides the best explanation of the evidence.