Knowledge
theory of knowledge · justified true belief
Traditionally defined as justified true belief; problematized by Gettier and beyond.
In practice
Someone predicts a downturn and is right. Whether they knew depends on whether their reasoning tracked the causes, or whether they were one of many guessing and happened to land well.
The common mistake
Treating confidence as evidence of knowledge. Confidence measures how firmly a belief is held, and Gettier cases show that even well-justified true beliefs can fall short.
Knowledge is the state of holding a belief that is both true and held for the right kind of reason. Distinguishing it from lucky true belief is the founding problem of epistemology.
Justified true belief
The traditional analysis sets three conditions. You know that P when P is true, you believe P, and you are justified in believing P. Each condition does work. Drop truth and you have confident error. Drop belief and you have information you do not hold. Drop justification and a correct guess would count.
In 1963 Edmund Gettier showed the three conditions can all hold while knowledge is absent. Suppose you look at a stopped clock at exactly the moment it happens to show the right time. Your belief is true, and you are justified in trusting a clock, yet you do not know. The justification and the truth are joined by accident. Sixty years of proposed fourth conditions have produced no consensus.
Kinds of knowing
Philosophers separate knowing that something is the case from knowing how to do something. Riding a bicycle is a competence rather than a stock of propositions, and describing it completely does not confer it. A third kind, knowledge by acquaintance, covers direct familiarity with a person or a color.
The Greeks marked a related distinction between episteme, secure and explanatory knowledge, and doxa, opinion that may happen to be right. Plato used it to argue that opinion is unstable until it is tied down by an account of why it is true.
Where it comes from
Empiricism traces all contentful knowledge to experience; rationalism holds that reason reaches some truths on its own; Kant argued that experience provides content while the mind provides structure. Skepticism presses on all three by asking what rules out systematic error.
Concept web
Open the full webQuestions
What is knowledge in philosophy?
Knowledge is traditionally analyzed as justified true belief — holding a belief that is true, for reasons that support it. Gettier cases show these conditions can be met by luck, so the analysis remains contested.
What is the difference between knowledge and belief?
Belief is holding something to be the case, whether or not it is true. Knowledge requires that the belief be true and be held on an adequate basis rather than by accident.
What is the difference between knowing that and knowing how?
Knowing that concerns facts and can be stated in propositions. Knowing how concerns skills and is a competence, which is why a complete description of riding a bicycle does not enable you to ride one.