Definitions of knowledge aim to identify the essential features of knowledge. Closely related terms are conception of knowledge, theory of knowledge, and analysis of knowledge. Some general features of knowledge are widely accepted among philosophers, for example, that it involves cognitive success and epistemic contact with reality. Despite extensive study, disagreements about the nature of knowledge persist, in part because researchers use diverging methodologies, seek definitions for distinct purposes, and have differing intuitions about the standards of knowledge.
An often-discussed definition asserts that knowledge is justified true belief. Justification means that the belief fulfills certain norms like being based on good reasons or being the product of a reliable cognitive process. This approach seeks to distinguish knowledge from mere true beliefs that arise from superstition, lucky guesses, or flawed reasoning. Critics of the justified-true-belief view, like Edmund Gettier, have proposed counterexamples to show that some justified true beliefs do not amount to knowledge if the justification is not genuinely connected to the truth, a condition termed epistemic luck.
