How did the fiction of Henry James offer a springboard to the modernism of 20th century literature?
As a progenitor of literary criticism, Henry James named or created many of the literary techniques we now take for granted. His view of literature was simple; a good writer produces good fiction, a bad writer produces bad fiction. His opinion on good or bad writing was based first in the realism of the text, then in interest to the reader, and finally in freedom of expression. James rejected the idea of overt symbolism dominating the story, and insisted that all literature, to be of worth, should be about the life and actions of characters who are interesting to the reader.
In his own works, James strove to keep the stories at the fore while experimenting with style and themes. His experiments with point-of-view included the third-person internal view, in which the reader sees a character from outside while still reading his inner thoughts; at the time, this was groundbreaking, and set the stage for later "stream of consciousness" novels, such as Jack Kerouac's On the Road.
Modern literature is far more experimental than the fiction of James's time, and it owes much of its freedom to his experiments. While others wrote about simple plots and simple characters, James was delving deeply into motivations and emotions without heed to accepted practice. In his view, any writer should be able to write about a topic in a way that was interesting, regardless of any other person's individual taste; he used point-of-view, internal monologue, overt and subtle symbolism, and narration in ways that led directly to the Impressionist, Abstract, and Modern movements in literature. Authors as diverse as Mark Z. Danielewski, James Joyce, Ezra Pound, Isaac Asimov, Hunter S. Thompson, and Robert Jordan have their roots in James's theories of view, character, and emotion.
In defying the literary conventions of the time, James was able to open up the field of literature to both a vast audience -- although his own work never achieved the status it has today in his lifetime -- and to the many writers who could not have been accepted in his time.