1. Critical Thinking Lecture 7a Gettier
By David Kelsey

2. Defining Knowledge Knowledge:
We saw in lecture 7 that knowledge is more than mere belief or even mere true belief.
Plato first defined knowledge as Justified True belief.

3. Knowledge as JTB Knowledge as JTB:
Thus, S knows that p if and only if:
S believes that p and
P is true and
S’s belief that p is justified
Individually Necessary:
Jointly sufficient:

4. Gettier & Knowledge Edmund Gettier Born in 1927
Philosophy professor at University of Massachusetts Amherst since 1967
In his article Is Justified True Belief Knowledge? Gettier argues that something’s being justified true belief is not a sufficient condition for it’s being knowledge.
Thus, he argues that one can have a justified true belief and yet not have knowledge.
Gettier provides two counterexamples to prove his point.

5. Smith, the job & 10 coins Smith, the job & 10 coins:
Smith believes that Jones is the man who will get the job and Jones has 10 coins in his pocket.
What is Smith’s justification for this belief?
So Smith infers that it is true that The man who will get the job has ten coins in his pocket.
But Smith gets the job & he has 10 coins in his pocket
So Smith has JTB without knowledge!

6. The Ford & Barcelona Now Smith gains evidence for the proposition:
That Jones owns a Ford (‘F’)
What’s Smith’s justification for this belief
So Smith Infers: Either Jones owns a Ford or Brown is in Barcelona. (‘A’)
What is Smith’s justification for this belief?
But Jones doesn’t own a Ford and Brown is in Barcelona
So Smith has JTB without knowledge again

7. Replies to Gettier Denying the assumptions: He assumes that:
1. It is possible for a person to be justified in believing a proposition that is false
2. Closure: for any proposition P, if S is justified in believing P and
P entails Q &
S deduces Q from P &
S accepts Q as a result of this deduction, then
S is justified in believing Q.
Example:
Snowing so Freezing

8. Denying Closure Denying closure:
We could deny Closure by holding an Externalist theory of justification.
For the Externalist, justification comes not from an inner mental state at all. Instead, it is something external to your mind which confers justification on a belief.
An Example:
Reliabilism: a belief is justified if it is formed through a reliable belief forming process

9. More replies to Gettier
Accepting the counterexamples: We might also reply to Gettier by accepting his counterexamples to the traditional definition of knowledge.
Finding another analysis: In this case we are then out to find a more adequate analysis of KNOWLEDGE.
Some examples:
Infallible justification
No false steps
No defeaters

10. Last thoughts on defining knowledge
What Gettier shows is that there is a bigger problem with conceptual analysis
A possible reply:
concepts like knowledge have a graded nature