Stopping by the one real barn in fake-barn country breaks the definition of knowledge
Imagine driving through a district full of convincing fake barns, unaware of the trick, and happening to stop at the only genuine one. You believe it is a real barn, you have good reason, and you are right. Most epistemologists still say you do not know it. Luck spoiled the old definition.
Epistemology, the theory of knowledge, studies what knowing is, where it comes from and how far it reaches. Its name joins the Greek episteme, knowledge, with logos, study, yet the term itself was only coined in the 19th century. Unlike psychology, which describes the beliefs people actually hold, epistemology is normative: it asks which ways of forming beliefs meet the standards knowledge demands.
Philosophers separate several kinds of knowing. Propositional knowledge is knowing that something is so, such as knowing that kangaroos hop. Knowing how is a practical skill, like preparing lasagna, while knowledge by acquaintance is familiarity through direct experience. A further split runs between a posteriori knowledge, drawn from the senses, and a priori knowledge, as in mathematics and logic; that divide sits at the heart of the quarrel between empiricists and rationalists.
The traditional analysis defined knowledge as justified true belief. In the second half of the 20th century, thought experiments like the barn case showed that epistemic luck can produce justified true beliefs that fall short. Proposed repairs require that the fact cause the belief in the right way, that a reliable process produce it, that the belief would vanish if false, or that it not rest on a falsehood. None has won consensus, and Timothy Williamson rejects the whole project, treating knowledge as a basic state that cannot be broken into parts.
Other disputes run just as deep. Radical sceptics claim nobody knows anything, while fallibilists accept knowledge without certainty. Coherentists judge a belief by how well it fits with others; foundationalists say basic beliefs need no such support. Internalists and externalists argue over whether justification depends only on the mind or also on the outside world. Reflection on these questions appears in ancient Greek, Indian and Chinese philosophy alike.
Source: Epistemology
