Edmund Gettier formulated the Gettier Problem in his 1963 paper, "Is Justified True Belief Knowledge?".

The central question of the Gettier Problem is whether it is possible to have a justified true belief that is not knowledge.

A Gettier case is a case in which a person has a justified true belief that is not knowledge. This is because there is some relevant information that the person does not know, which would have prevented them from having a justified belief.

The traditional definition of knowledge is justified true belief. This means that in order to know something, one must have a true belief that is justified by evidence or reason.

The problem with the traditional definition of knowledge is that it is too narrow. It excludes cases in which a person has a justified true belief that is not knowledge, such as in Gettier cases.

There are a number of proposed solutions to the Gettier Problem, including revising the definition of knowledge, rejecting the principle of closure, and adopting a reliabilist theory of knowledge.

The principle of closure is the principle that if one knows that p and one knows that p implies q, then one knows that q.

A reliabilist theory of knowledge is a theory of knowledge that holds that knowledge is justified true belief that is produced by a reliable process.

One criticism of reliabilist theories of knowledge is that they are too narrow. They exclude cases in which a person has a justified true belief that is not knowledge, such as in cases where the person's belief is produced by a lucky guess.

It is likely that the Gettier Problem will remain unsolved. This is because it is a deep and difficult problem that raises fundamental questions about the nature of knowledge.