Gettier Quote on Justified True Belief: The Famous Counterexample

Quote

"The following two conditions are not sufficient for S to know that P: (i) P is true, (ii) S believes that P, and (iii) S is justified in believing that P."

— Edmund Gettier, "Is Justified True Belief Knowledge?" (Analysis, 1963)

Context

This passage appears in "Is Justified True Belief Knowledge?," a paper published in the journal Analysis in 1963. The paper is barely three pages long — yet it transformed epistemology more than any single publication in the 20th century.

Before Gettier, the standard definition of knowledge held that knowledge is justified true belief (JTB). This analysis traces back to Plato's Theaetetus and was revived in modern form by figures like A.J. Ayer and Roderick Chisholm. On this view, to know something, three conditions must be met:

1. The proposition must be true (you can't know something false)
2. You must believe it (you can't know something you don't believe)
3. Your belief must be justified (you can't know something merely by lucky guessing)

This seemed, for centuries, to be the correct analysis. Gettier showed it was not. In a few elegant paragraphs, he constructed cases — now called "Gettier cases" — where all three conditions are satisfied, yet the person clearly does not have knowledge.

In the first Gettier case, Smith and Jones have applied for the same job. Smith has strong evidence that Jones will get the job (the company president told him so) and that Jones has ten coins in his pocket (Smith counted them). Smith infers: "The man who will get the job has ten coins in his pocket." But it turns out that Smith himself gets the job, and Smith happens to have ten coins in his own pocket. So his belief is true, he believes it, and he's justified — but he doesn't know it. His justification pointed to Jones, but the truth happened to align with Smith by coincidence.

Meaning

Gettier's claim is deceptively simple but philosophically devastating. He is saying that the three conditions — truth, belief, and justification — can all be satisfied by accident. The believer can be justified, right, and sincere, yet still fail to know.

This reveals something deep about knowledge: it requires more than just getting the right answer for good reasons. It requires the right answer to be connected to the right reasons in the right way. In Gettier's cases, the truth of the belief is disconnected from the justification — the justification supports the belief through one path (Jones will get the job and has ten coins), but the truth comes about through a different path (Smith gets the job and has ten coins). This mismatch — what epistemologists call "epistemic luck" — is what prevents the belief from counting as knowledge.

The key insight is that justification can be misleading. You can have excellent reasons for a belief that happen, through no fault of your own, to point to the wrong explanation for why the belief is true. When this happens, you have a justified true belief that is not knowledge. The gap between justification and truth is where Gettier cases live.

Philosophical Significance

Gettier's paper launched what is now called "the Gettier problem" — the search for a fourth condition, or a replacement analysis, that would handle the counterexamples. The paper is often cited as one of the most influential in the history of philosophy relative to its length.

The fourth condition debate: Epistemologists proposed dozens of "fourth conditions" to supplement JTB — conditions like "no false lemmas" (the belief must not be inferred from any false premise), "defeasibility" (there must be no defeating evidence the believer doesn't possess), and "reliability" (the belief-forming process must be generally reliable). Each proposal faced new counterexamples, leading to an ongoing dialectic that continues today.

Reliabilism: One major response was to abandon the internalist focus on justification altogether. Alvin Goldman argued that knowledge is true belief produced by a reliable cognitive process — one that tends to produce true beliefs. This shifted epistemology toward naturalistic and externalist approaches.

Virtue epistemology: Ernest Sosa and others developed virtue epistemology, which analyzes knowledge in terms of intellectual virtues — stable character traits that produce true beliefs. A belief counts as knowledge when it arises from an intellectual virtue, not just from justified belief.

Practical epistemology: Gettier cases aren't just academic puzzles. They arise in real-world contexts — legal evidence, scientific inference, medical diagnosis — where the distinction between knowing and merely having a justified true belief matters practically. A doctor who correctly diagnoses a patient based on misleading evidence may have a "Gettiered" belief, and the difference between that and genuine knowledge can affect treatment decisions.

Contemporary relevance: The Gettier problem remains unsolved. No proposed analysis of knowledge has achieved consensus. This has led some philosophers to question whether knowledge has a unified nature at all, while others continue the search for the right analysis. The longevity of the problem testifies to the depth of Gettier's insight: the gap between justification and truth is real, and bridging it is harder than it looks.

Sources

1. Gettier, E. (1963). "Is Justified True Belief Knowledge?" Analysis, 23(6), 121-123. Available at: https://www.jstor.org/stable/3326922
2. "The Analysis of Knowledge," Stanford Encyclopedia of Philosophy. Available at: https://plato.stanford.edu/entries/knowledge-analysis/
3. "The Gettier Problem," Internet Encyclopedia of Philosophy. Available at: https://iep.utm.edu/gettier/
4. "Epistemology," Internet Encyclopedia of Philosophy. Available at: https://iep.utm.edu/episte/
5. Ichikawa, J.J. & Steup, M. (2018). "The Analysis of Knowledge," Stanford Encyclopedia of Philosophy. Available at: https://plato.stanford.edu/entries/knowledge-analysis/