Gettier Cases

Since Plato’s Theaetetus, knowledge has often been taken to be justified true belief.

For example, Kenley knows his door is locked if and only if:

The Gettier Problem

Edmund Gettier showed that this account is not sufficient to produce knowledge.

Consider the following case.

After Philosophy Club, Kenley puts the key into the lock on his classroom door, turns it, and then pulls on the door to see if it opens.

The door does not open.

Kenley goes home, and his wife asks, “Is the door to your classroom locked?”

He says, “I know it is locked because I put the key in the lock, turned it, and then pulled it to see if it would open.”

However, unbeknownst to him, the door did not lock when he did his routine.

There was a very rare malfunction that made it seem locked for a second, but then the door was left wide open.

A custodian saw the open door, closed it, and locked it, with the result that it really was locked this time.

Kenley believes the door is locked.

The door is locked.

Kenley has good reasons to believe the door is locked.

So Kenley has a justified true belief that the door is locked.

But it still seems like Kenley does not really know that the door is locked.

Therefore, justified true belief is not sufficient for knowledge.

If these Gettier cases really work, do we ever have knowledge of anything?
What is so great about knowledge in the first place?
Even if Kenley knows the door is locked, can he ever know that he knows?
What kinds of justification can a person give for claiming to know something? Who gets to decide what is good justification and what is bad justification?
Are there any rules for when a person says that something is true? Does Kenley need to know that the door is locked in order to say that the door is locked? Who decides those rules?