In the arts and literature, the term avant-garde identifies an experimental genre or work of art, and the artist who created it, which usually is aesthetically innovative, whilst initially being ideologically unacceptable to the artistic establishment of the time. The military metaphor of an advance guard identifies the artists and writers whose innovations in style, form, and subject-matter challenge the artistic and aesthetic validity of the established forms of art and the literary traditions of their time; thus, the artists who created the anti-novel and surrealism were ahead of their times.