Recently, it has been argued that the 18th-century realist tradition (Balzac, Dickens and on to now) is not the only such tradition; there is also an earlier, nonrealist one, exemplified by Sterne, Diderot and Fielding and taking writing rather than realism as its subject. As Stephen Spender put it, "the mode of perceiving itself becomes an object of perception."
This alternate tradition, long eclipsed, emerged in the early decades of the last century and became known as Modernism. It revolutionized the arts. Painters abandoned representation and called attention to canvas, brush strokes and the paint itself. Composers challenged conventional tonality. Writers, novelists in particular (Joyce, Gide, Proust, Virginia Woolf, Henry Green), challenged realist conventions of narrative.
There were reasons -- economic, sociological and political -- for this. All indicate that the assumptions of realism (certainty, assuredness, common morality) no longer existed. The world was not to be reflected in a single manner. Rather, the means were to be many, doubt was a major assumption, omniscience was no longer possible, and the method itself -- writing -- must be questioned.