What kind of knowledge is chiefly analyzed by asking what it takes for someone to know that a statement is true?
Choose an answer, then check it.
Philosophy & Ethics · Foundations
What Is Knowledge?
On this page 9 sections
In 30 seconds
Knowledge is more demanding than simply having an opinion that happens to be correct. When philosophers analyze knowledge of a fact, they commonly ask whether the person believes the claim, whether it is true, and what supports the belief A person's attitude of taking a proposition to be true, whether or not that proposition is actually true. Full entry →. The traditional answer, justified true belief A traditional analysis that treats truth, belief, and justification as central conditions for propositional knowledge. Full entry →, is a useful starting point—but counterexamples show that a justified true belief can still be true by luck.
Why this matters
Knowledge claims guide decisions: a nurse reports a result, a student cites a source, and a voter shares a claim. Calling something knowledge usually gives it more weight than a hunch or a rumor. Studying the concept helps us identify what evidence supports a claim, distinguish being right from arriving at the truth The condition of a proposition accurately representing how things are, rather than merely seeming correct to someone. Full entry → responsibly, and describe uncertainty honestly. It also reveals why careful inquiry can matter even when people agree about a conclusion.
The college version
The target: knowing that something is so
The sharpest philosophical question about knowledge concerns propositional knowledge Knowledge that a particular statement or proposition is true, often expressed as knowing that something is the case. Full entry →: knowing that a particular statement is true. If Jordan knows that the bridge is closed, the relevant claim is the proposition that the bridge is closed. This is different from knowing a person, knowing a city, or knowing how to perform a skill. Those uses of the word knowledge matter, but an introductory analysis needs a manageable target. It asks what has to be true of a person and a proposition for the person to know that proposition.
A belief is not enough. People can believe claims that are false, and a correct guess may be true without being knowledge. Truth therefore matters: one cannot know, as a fact, a proposition that is false. Yet truth alone is not enough either. If a contestant circles an answer at random and is correct, the contestant has a true belief, but the success looks accidental. Philosophers use such cases to explain why a knowledge claim asks not only whether a conclusion is right, but also how the person came to hold it.
This does not mean that every ordinary use of “I know” announces a complete philosophical theory. In conversation, the phrase can signal confidence, responsibility, or a practical commitment to act. The analysis of knowledge instead isolates a conceptual question: what conditions would make a claim to propositional knowledge genuinely warranted? It is a project of clarification, not a shortcut that decides every disputed factual question.
Justified true belief: a powerful starting proposal
A traditional proposal says that a person knows a proposition only if three conditions are met: the proposition is true, the person believes it, and the person is justified in believing it. The shorthand is JTB, for justified true belief. Each condition does distinct work. Truth rules out claims that merely feel correct. Belief marks a connection between the person and the claim: someone who has no belief that the bridge is closed does not know that it is closed. justification Reasons, evidence, or support offered for holding a belief, distinct from the belief's eventual truth. Full entry → asks whether the belief rests on reasons, evidence, or a method that makes the belief intellectually responsible.
The proposal is attractive because it separates knowledge from two nearby cases. A lucky guess may be true but unsupported. A carefully investigated claim can be well supported yet turn out false because the evidence was misleading or incomplete. JTB treats knowledge as requiring both success and an appropriate epistemic basis. It also gives students a useful checklist for modest claims: What exactly is being asserted? Is it true? Does the person actually take it to be true? What information, reasoning, or experience supports that belief?
The checklist is not a recipe that turns any source into knowledge. “Justification” is itself a philosophical problem. Evidence may be incomplete, a source may be reliable in one setting but not another, and people disagree about how much support is enough. The JTB account is thus best taught as an influential analysis, not as a final definition endorsed by every philosopher. It frames the dispute rather than ending it.
Why luck creates the Gettier problem
Gettier-style counterexamples challenge the claim that justified true belief is sufficient for knowledge. Consider a campus workshop. Mira sees the digital display listing the workshop in Room 214. The display has reliably listed rooms all semester, so she has a reasonable basis for believing the workshop is in Room 214. Unknown to Mira, the display has frozen with an old listing. By coincidence, an organizer moved the workshop back to Room 214 only minutes ago. Mira believes a true proposition and has what seems like justification, yet the connection between her evidence and the truth is accidental. Many philosophers judge that she did not know the room assignment.
The point is not that Mira behaved foolishly. Her evidence made belief reasonable. The point is that a belief can be true and justified while succeeding through luck. Cases of that structure are commonly called Gettier cases, after Edmund Gettier’s influential 1963 paper. They pressure a proposed analysis by presenting a case that appears to meet its listed conditions but still fails to count as knowledge. A successful account needs to explain why the apparent match is not enough.
Responses vary. Some philosophers try to specify a stronger kind of justification. Others add a condition intended to rule out an accidentally true belief, such as a requirement involving the belief's connection to the fact or the absence of defeating information. Those proposals also attract objections and new cases. The enduring lesson is modest but important: evidence, truth, and belief must be examined together, and a good-looking checklist can hide a gap between being right and knowing.
Eli explains
The same idea, in plain words
Explain it like I’m 10
Saying “I know” is stronger than saying “I think.” Imagine you say the school is closed because you saw a notice. For your claim to be knowledge, it should be true, you should actually believe it, and you should have a good reason for believing it. Philosophers call that older three-part idea justified true belief. But they also ask whether your reason really led you to the truth, or whether you just got lucky.
Picture it like this
Think of knowledge as arriving at the right house using a map. Reaching the correct address matters, and having a map matters. But if your map is wrong and a gust of wind happens to blow you onto the right street, you got there by luck. Philosophers ask whether a knowledge claim reached the truth in a better-connected way.
Where the picture stops working
A belief is not literally a trip, and evidence does not work like a paper map. People can have several reasons, revise them, or disagree about how reliable they are. The analogy only highlights the difference between ending up correct and being guided to the truth by an appropriate basis.
Worked example
A student, Ana, tells her group that the assignment deadline is Friday because a course webpage says so. The page is normally reliable, and the deadline really is Friday. That initially looks like a justified true belief. Before calling it knowledge, however, ask why the page says Friday. If Ana read the current course page, her evidence is connected to the fact. If the page was an outdated copy that happened to show Friday while the instructor independently changed the deadline back to Friday that morning, Ana's belief is true by coincidence. Her belief may still have been reasonable, but the case illustrates why philosophers ask whether justification and truth are appropriately connected.
Key takeaway
Knowledge is not simply confidence or a correct answer. The traditional justified-true-belief account explains why belief, truth, and reasons matter, while Gettier-style cases show why philosophers continue to ask whether a true belief reaches the truth without accidental luck.
Quick check
3 questions here, of 5 in this lesson’s practice set. Answers stay hidden until you check.
Which combination names the three central conditions in the traditional justified-true-belief account?
Choose an answer, then check it.
Which scenario is the best example of the luck problem raised by a Gettier-style case?
Choose an answer, then check it.
Study tools & related lessonsYou’ll learn to · Common mistakes · Easily confused · Key vocabulary · Related
You’ll learn to
- Define propositional knowledge and distinguish it from belief, truth, and justification.
- Explain the traditional justified-true-belief analysis as a proposed account of knowledge.
- Use a Gettier-style case to show why justified true belief may be insufficient for knowledge.
- Apply the distinction between a true belief and knowledge to an everyday information claim.
- State why the analysis of knowledge remains philosophically contested.
Common mistakes
Treating a true belief as automatically knowledge.
A true belief can be a lucky guess; philosophical accounts ask what support and connection to truth are present.
Treating justified true belief as an undisputed final definition.
It is an influential traditional analysis, but Gettier-style cases challenge its sufficiency and later proposals remain debated.
Assuming a Gettier case shows that evidence never matters.
The case shows that apparently adequate evidence plus truth may not settle knowledge; it does not make evidence irrelevant.
Calling every error a Gettier case.
A Gettier-style problem involves a belief that is true and apparently justified but true in an accidental way, not a plainly false claim.
Easily confused
True belief vs. Propositional knowledge
A belief that happens to be correct versus the more demanding status philosophers analyze using truth, belief, justification, and anti-luck concerns.
Justification vs. Truth
A person's reasons or support for a belief versus whether the believed proposition actually matches how things are.
Reasonable belief vs. Lucky success
A belief can be reasonable on the evidence available while its truth is still accidental because the evidence is disconnected from the fact.
Key vocabulary
- propositional knowledge
- Knowledge that a particular statement or proposition is true, often expressed as knowing that something is the case.
- belief
- A person's attitude of taking a proposition to be true, whether or not that proposition is actually true.
- truth
- The condition of a proposition accurately representing how things are, rather than merely seeming correct to someone.
- justification
- Reasons, evidence, or support offered for holding a belief, distinct from the belief's eventual truth.
- justified true belief
- A traditional analysis that treats truth, belief, and justification as central conditions for propositional knowledge.
- Gettier case
- A counterexample in which a belief appears justified and true but seems true through luck rather than knowledge.
- epistemic luck
- Good fortune in a belief's being true when its truth is not appropriately connected to the person's basis for believing it.
- defeater
- Information that would weaken or undermine a person's justification for holding a particular belief.
Sources & references
- 7.2 Knowledge — Introduction to Philosophy — OpenStax, Rice University
- The Analysis of Knowledge — Stanford Encyclopedia of Philosophy, Metaphysics Research Lab, Stanford University
EliExplains lessons are original prose written from the open, credible references above. See Copyright & Licensing.
Researched 2026-08-20
Educational content only. It is not medical, legal or professional advice. Found an error? Tell us.