A direct answer
A Gettier case is designed so that a belief is true, believed, and supported by apparently good reasons, while its truth still seems accidental. The cases show why justified true belief is not widely accepted as a sufficient account of knowledge, but they do not establish one agreed replacement.
Questions hidden inside
- Why can a true belief supported by reasonable evidence still fall short of knowledge?
- What kind of luck is incompatible with knowing?
- Should knowledge require reliable methods, safe belief, intellectual competence, or the absence of defeating evidence?
- What do Gettier cases reveal about the limits of defining a concept by a short checklist?
Philosophical lenses
Epistemic luck
How is the belief’s truth related to the person’s grounds?
A Gettier case makes the final belief true while allowing misleading circumstances to sever the expected route from evidence to fact.
Conceptual analysis
Can necessary and sufficient conditions define knowledge?
The case tests a proposed analysis and motivates revisions, while repeated counterexamples raise questions about the project itself.
Responsible inquiry
What practices reduce accidental truth?
Checking sources, testing instruments, seeking defeaters, and using reliable methods can improve inquiry even without a settled definition of knowledge.
Begin with a choice
Mara reads a normally reliable station display saying that the 8:10 is on time. The display is frozen, but the train happens to be on time anyway. Does Mara know that it is on time?
The justified-true-belief proposal
A familiar analysis says that a person knows a proposition when three conditions are met: the proposition is true, the person believes it, and the person is justified in believing it. Truth excludes successful belief in something false, belief excludes facts the person never accepts, and justification excludes a lucky guess.
Gettier’s 1963 paper challenged the sufficiency of this three-part analysis. His cases arrange two pieces of luck: apparently good evidence points toward a falsehood, while an unexpected fact makes the resulting belief true. The person reaches the truth, but not in the way the evidence suggests.
| Condition | What it rules out | What a Gettier case preserves |
|---|---|---|
| Truth | Believing what is false | The final proposition is true |
| Belief | A truth the person does not accept | The person sincerely believes it |
| Justification | A bare guess with no support | The person has apparently good evidence |
| Non-accidental connection | Reaching truth in the wrong way | This is the missing feature the case exposes |
A contemporary explanatory case
Imagine that Mara checks a station display, which shows that the 8:10 train is on time. The display normally receives accurate live data, so she believes with good reason that the 8:10 is on time. Unknown to her, the data feed froze yesterday and the display has been repeating an old message. By coincidence, today’s 8:10 really is on time after a separate delay was resolved.
Mara’s belief is true, she believes it, and her evidence looks reasonable from her position. Still, many people hesitate to say that she knew. The broken connection between the display and today’s train makes the truth of her belief accidental. This is a site-created teaching example with the structure of a Gettier case, not one of Gettier’s original examples.
The problem is not ordinary uncertainty alone. It is a mismatch between why the person believes and what actually makes the belief true.
Several repairs compete
One proposal adds a no-false-steps condition: knowledge must not be inferred through a false premise. That handles many early cases but not examples in which luck enters without a clear false inference. Reliabilist approaches ask whether the belief-forming process generally produces truth. Safety approaches ask whether the person could easily have been wrong in nearby circumstances.
Other accounts emphasize intellectual competence, the absence of undefeated counterevidence, a suitable causal connection to the fact, or knowledge as a basic notion that should not be reduced to belief plus further conditions. Each approach explains some intuitions and faces counterexamples or questions about how its central condition should be understood.
- No false steps: did the reasoning depend on a false proposition?
- Reliability: does this method tend to produce true beliefs in relevant conditions?
- Safety: could the same method easily have produced a false belief nearby?
- Virtue: is the truth attributable to the person’s intellectual competence?
- Defeaters: is there overlooked information that would undermine the justification?
A counterexample opens a research program
The Gettier Problem shows the power of a counterexample. A definition that fits many ordinary cases may still fail if its conditions can all be satisfied in a case that clearly lacks the target feature. Philosophers then test revised accounts against new cases, including fake environments, misleading evidence, reliable processes, and different kinds of luck.
Intuitions about unusual stories are evidence to examine, not final verdicts detached from theory. A useful discussion asks which detail breaks knowledge, whether the judgment changes across cultures or descriptions, and what work a theory of knowledge should perform in inquiry, testimony, science, law, and daily life.
Change one fact
Does independent, truth-connected confirmation turn the belief into knowledge?
Your earlier choice: Judge the case when the frozen display coincidentally matches the train’s actual status.
Continue with knowledge, justification, truth, epistemic luck.
Continue with Ada
Professor Ada Rowan
Test an idea or objection
Compare perspectives, test an assumption, or develop an objection using this reviewed page as context.
Related paths
Sources
- Is Justified True Belief Knowledge? — Edmund L. Gettier (1963)
Gettier’s short paper presents counterexamples to analyses on which justified true belief is sufficient for knowledge. It is the primary source for the modern Gettier problem and supports explaining the logical structure of the cases without treating one repair as settled.
View source - The Analysis of Knowledge (2026)
Current scholarly survey of attempts to analyze propositional knowledge, the justified-true-belief account, Gettier counterexamples, epistemic luck, no-false-lemma proposals, safety, sensitivity, reliabilism, virtue approaches, and knowledge-first alternatives.
View source
Last modified 2026-07-31. Reviewed by Thinking Paths editorial team.