Thus the canon of Shakespeare's plays includes 37 plays generally considered to be certainly his, but there are a number (such as the anonymous Arden of Faversham) which are apocryphal.
The concept of a canon has come under review in recent years, as it has become clear that cultural preconceptions have a profound influence on what is considered to be of literary value; the result of such preconceptions has been, for example, to reduce the value attributed to works of literature written by women in earlier periods.