Gettier's Three Pages and the Collapse of a Definition Philosophy Had Relied On

For most of the twentieth century, epistemology treated the definition of knowledge as close to settled: a person knows a proposition just in case they believe it, it is true, and they are justified in believing it, the tripartite justified true belief analysis with roots traceable to Plato's Theaetetus. In 1963 Edmund Gettier published a paper barely three pages long, Is Justified True Belief Knowledge, that described two cases in which a person holds a justified true belief that nearly every reader's intuition refuses to call knowledge, typically because the belief turns out true only by a lucky accident unrelated to the reasoning that justified it.

The paper reorganized the field almost overnight. Rather than treating the tripartite analysis as adequate with minor repairs, epistemologists spent the following decades proposing entirely different accounts of what closes the gap a Gettier case exposes, Alvin Goldman's causal and later reliabilist theories tying knowledge to the process that produced the belief rather than to the believer's own justification, Robert Nozick's tracking account asking whether the belief would have been different had the fact been otherwise, and Bernard Williams and others eventually questioning whether knowledge admits of a tidy definition in the first place. Post Gettier epistemology is still the field's standard label for work written after 1963, a rare case of a single short paper renaming an entire area of philosophy by what came after it rather than by its subject matter.