Study of the origin, nature, and limits of human knowledge.
Nearly every great philosopher has contributed to the epistemological literature. Some historically important issues in epistemology are: (1) whether knowledge of any kind is possible, and if so what kind; (2) whether some human knowledge is innate (i.e., present, in some sense, at birth) or whether instead all significant knowledge is acquired through experience (see empiricism ; rationalism ); (3) whether knowledge is inherently a mental state (see behaviourism ); (4) whether certainty is a form of knowledge; and (5) whether the primary task of epistemology is to provide justifications for broad categories of knowledge claim or merely to describe what kinds of things are known and how that knowledge is acquired. Issues related to (1) arise in the consideration of skepticism , radical versions of which challenge the possibility of knowledge of matters of fact, knowledge of an external world, and knowledge of the existence and natures of other minds .