Legend is a genre of folklore that consists of a narrative featuring human actions perceived or believed both by teller and listeners to have taken place within human history. Narratives in this genre may demonstrate human values, and possess certain qualities that give the tale verisimilitude. Legend, for its active and passive participants, includes no happenings that are outside the realm of "possibility," but may include miracles. Legends may be transformed over time, in order to keep them fresh, vital, and realistic. Many legends operate within the realm of uncertainty, never being entirely believed by the participants, but also never being resolutely doubted.