Book notes on Gettier

(Originally written September 15, 2006 in Book 8)

Part IV The Analysis of Knowledge

IV. 1 Is justified true belief knowledge?

Edmund Gettier (1927 - )

Plato:

S knows P if
1) P is true
2) S believes P
3) S is justified in believing P

Chisholm:

S knows P if
1) S accepts P
2) S has adequate evidence that P is true
3) P is true

Ayer:

S knows P if
1) P is true
2) S is sure that P is true
3) S has the right to be sure that P is true

Case I: Suppose S & J have each applied for the same position.

S has strong evidence for proposition "D".

"D" - Jones is the man who will get the job and Jones has 10 coins in his pocket.

Proposition "D" entails the man who will get the job has ten coins in his pocket.

But in fact S gets the job and buy chance he has ten coins in his pocket.

Proposition "D" turns out to be true and despite knowing with a justified belief that "D" is true he couldn't have possibly had knowledge of it.

Case II: S has strong evidence for proposition "F", Jones owns a Ford.

S has a friend named B, but has no idea where B is.

Therefore S can state
1) J owns a Ford or B is in Boston
2) J owns a Ford or B is in Barcelona
3) J owns a Ford or B is in Bologna

In fact, Jones does not own a Ford and B is in Boston. That makes proposition 1 true, but in spite of his evidence, S had no knowledge of it.