The historical period we are living through has been singularly uncertain, insecure, self-questioning and culturally pluralistic. Contemporary fiction clearly reflects this dissatisfaction with, and breakdown of, traditional values. Previously, as in the case of nineteenth-century realism, the forms of fiction derived from a firm belief in a commonly experienced, objectively existing world of history. Modernist fiction, written in the earlier part of this century, responded to the initial loss of belief in such a world. [...] Contemporary metafictional writing is both a response and a contribution to an even more thoroughgoing sense that reality or history are provisional: no longer a world of eternal verities but a series of constructions, artifices, impermanent structures.
This 'thoroughgoing' awareness of the 'provisional', 'constructed' character of reality and history is expressed, according to Brian McHale, by a shift from mainly 'epistemological' questions as the 'dominant' (the position from which the world is interrogated) of the previous literary period, for example 'How can I interpret this world of which I am part?', to mainly 'ontological' questions, for example 'what and how is this world?,' as the `dominant' of the new trend of metafictional literature. This shift in the literary interrogation of the world is equated by Waugh, Federman and McHale to the shift from modernist to postmodernist literature. Therefore, this literary trend is often labelled as 'postmodernist metafiction' (which is also the term that Wallace uses).
quoted from Waugh's Metafiction (book 49)