The history of avant-garde film in the twentieth century can be defined by a widely accepted canon of major works and artists, although the function of this canon changed between the pre-World War II pioneer period and the 1960s, when avant-garde film emerged as a challenge to conventional narrative. A more dialectical conception of the avant-garde, proposed by Peter Wollen, has since served to unite different traditions, until recent concerns have emerged about the very idea of a film-based canon. New studies have emphasised the importance of networks and of contexts of presentation as perhaps greater than the film-texts themselves. More varied contemporary forms of access to avant-garde film may eventually supersede the traditional Modernist canon.