Epistemology is the branch of philosophy concerned with knowledge. Epistemologists study the nature, origin, and scope of knowledge, epistemic justification, the rationality of belief, and various related issues. Debates in contemporary epistemology are generally clustered around four core areas:The philosophical analysis of the nature of knowledge and the conditions required for a belief to constitute knowledge, such as truth and justification;
Potential sources of knowledge and justified belief, such as perception, reason, memory, and testimony
The structure of a body of knowledge or justified belief, including whether all justified beliefs must be derived from justified foundational beliefs or whether justification requires only a coherent set of beliefs; and,
Philosophical scepticism, which questions the possibility of knowledge, and related problems, such as whether scepticism poses a threat to our ordinary knowledge claims and whether it is possible to refute sceptical arguments.
Bertrand Russell famously brought attention to the distinction between propositional knowledge and knowledge by acquaintance
The analytic–synthetic distinction was first proposed by Immanuel Kant.
David Hume, one of the most staunch defenders of empiricism
René Descartes, who is often credited as the father of modern philosophy, was often preoccupied with epistemological questions in his work.
Knowledge is an awareness of facts, a familiarity with individuals and situations, or a practical skill. Knowledge of facts, also called propositional knowledge, is often characterized as true belief that is distinct from opinion or guesswork by virtue of justification. While there is wide agreement among philosophers that propositional knowledge is a form of true belief, many controversies focus on justification. This includes questions like how to understand justification, whether it is needed at all, and whether something else besides it is needed. These controversies intensified in the latter half of the 20th century due to a series of thought experiments called Gettier cases that provoked alternative definitions.
The owl of Athena, a symbol of knowledge in the Western world
Declarative knowledge can be stored in books.
Knowing how to ride a bicycle is one form of non-propositional knowledge.
Perception relies on the senses to acquire knowledge.
