William Dean Howells of the Atlantic Monthly tried to define realism as writing exactly what is seen in real life with ordinary people, but they then would eventually be victorious because of their good qualities. This in itself became unrealistic. These writers weighed heavily on the psychology and sociology of human beings. The naturalists attempted to dissect characters and the human behavior by determining that humans had no control over their lives. Forces beyond the power of the individual worked against him.
Humans have few choices and are totally subject to the natural laws of the universe.
Ernest Hemingway and Kurt Vonnegut are also in this category of writers.