The Western canon is a term use to denote a canon of books, and, more widely, music and art, that has been the most influential in shaping Western culture. It asserts a compendium of the "greatest works of artistic merit". Such a canon is important to the theory of educational perennialism and the development of "high culture". Although previously held in high regard, it has been the subject of increasing contention through the latter half of the 20th century. In practice, debates and attempts to actually define the Canon in lists are essentially restricted to books of various sorts: Literature, including Poetry, Fiction and Drama, autobiographical writings and Letters, Philosophy and History. A few accessible books on the Sciences are usually included.