(from the Greek words episteme (knowledge) and logos (word/speech)) The branch of philosophy that deals with the nature, origin and scope of knowledge. Historically, it has been one of the most investigated and most debated of all philosophical subjects. Much of this debate has focused on analysing the nature and variety of knowledge and how it relates to similar notions such as truth and belief. Much of this discussion concerns the justification of knowledge claims, that is the grounds on which one can claim to know a particular fact.