Epistemology i/ɨˌpɪstɨˈmɒlədʒi/ (from Greek ἐπιστήμη (epistēmē), meaning "knowledge, understanding", and λόγος (logos), meaning "study of") is the branch of philosophy concerned with the nature and scope of knowledge. It questions what knowledge is, how it is acquired, and to what extent it is possible for a given subject or entity to be known.
Much of the debate in this field has focused on analyzing the nature of knowledge and how it relates to connected notions such as truth, belief, and justification. One view, skepticism, is the objection that there is very little or no knowledge at all.
The term was introduced by the Scottish philosopher James Frederick Ferrier (1808–1864). The field is sometimes referred to as the theory of knowledge.