What is the Gettier problem about knowledge?

The Gettier problem is a challenge to the old view that knowing something just means having a justified true belief in it. Gettier cases are situations in which someone holds a belief that is true and well supported by evidence, yet which almost all epistemologists judge not to be knowledge. The problem is named after the American philosopher Edmund Gettier, who set it out in 1963. [1] [2]

Before Gettier, the standard analysis had three parts. The person must believe the proposition, the proposition must be true, and the belief must be justified, meaning backed by good evidence or reasoning. Without justification, a true belief might be only a lucky guess. The analysis treated these three conditions as individually necessary and jointly sufficient for knowledge. OpenStax links this account to Plato and calls it the traditional account of knowledge. [1] [2]

In the best-known case, Smith and Jones have both applied for a job. The company president has told Smith that Jones will get it, and Smith has counted ten coins in Jones's pocket. Smith infers that whoever gets the job has ten coins in their pocket. That belief is reasonably well justified. It also turns out to be true, but for reasons Smith did not expect: Smith himself gets the job, and Smith himself has ten coins in his pocket. Gettier judged that Smith does not know this, even though the belief is true and justified. [1]

If that reading is right, being true and justified does not suffice for knowledge. This does not show that belief, truth or justification is unnecessary, only that something more is missing. Gettier himself made no suggestion about what to put in its place. [1] [2]

The Internet Encyclopedia of Philosophy says such cases share two features. First, the justification is fallible: it strongly indicates the belief is true without proving it, so the belief could have been false. Second, luck is involved. Some unusual circumstance makes it fortuitous that the belief is both justified and true. In Smith's case, the belief was made true by facts his evidence never noticed. OpenStax adds that Gettier was not the first to give such a counterexample, but his paper was the influential one, so any similar example is now called a Gettier case. [1] [2]

Almost all epistemologists agreed that Gettier had refuted the traditional definition, and the paper set off many attempts to repair or replace it, producing new conceptions of knowledge and of justification. The Stanford Encyclopedia notes that neither adequate evidence nor reliable faculties, nor both together, is enough to guarantee that a belief is knowledge. The Internet Encyclopedia reports that there is still no consensus that any proposed solution fully defines knowledge, so the challenge is still felt in epistemology. [1] [3]