Knowledge (episteme in Greek, Wissen in German) is the central concern of epistemology — the branch of philosophy that asks what knowledge is, how it is possible, and what its limits are. The tripartite analysis (justified true
belief) is ancient (Plato's "Meno" and "Theaetetus") but was challenged in 1963 by Gettier's counterexamples, which showed that justified true belief is not sufficient for knowledge. Rationalism (Descartes, Leibniz, Spinoza) holds that genuine knowledge is a priori — accessible through reason alone, independent of sensory experience. Empiricism (Locke, Berkeley,
Hume) holds that all knowledge derives
ultimately from sensory experience. Kant's "critical" philosophy attempts a synthesis: a priori categories of the understanding structure sensory experience to produce genuine knowledge. Foucault's concept of the épistème (the historically specific conditions that determine what counts as knowledge) historicizes the concept. For poets, the claim to knowledge raises the question of what kind of truth the poem can deliver. Related terms: justified true belief, Gettier counterexamples, a priori/a posteriori, Foucault's épistème, epistemic virtue, testimony.