Upon first glance, naturalism and realism seem interchangeable. Both focus on presenting an unromantic picture of everyday life. However, the philosophical and even ideological aims of naturalism and realism are dissimilar. In brief, naturalism takes a pessimistic view of human nature while realism does not necessarily adopt such views.
Naturalism accepts a deterministic vision of the universe, as it was highly influenced by Darwin's theories of evolution and survival of the fittest. It experienced its highest vogue between the 1880s and 1910s. In naturalist fiction, human beings are controlled by the environment in which they find themselves, not by free will.
For example, in Frank Norris' naturalist novel McTeague, the main characters, Mcteague and Trina, descend into almost animalistic behaviors when they are forced into poverty. Their backgrounds are also linked with their negative actions as well: McTeague is from a poor family and had a brutish drunk for a father, which predestines him to end his days a drunk brute despite enjoying a brief period of middle-class success as a dentist.
Even Trina is ruled by urges beyond her control. She starts as a placid, easygoing woman, but when she meets McTeague, desires Norris paints as inherent to her being a woman emerge—in this case, a sense of romantic and sexual submission to McTeague's overwhelming virility:
At once there had been a mysterious disturbance. The woman within her suddenly awoke.
Did she love McTeague? Difficult question. Did she choose him for better or for worse, deliberately, of her own free will, or was Trina herself even allowed a choice in the taking of the step that was to make or mar her life? The Woman is awakened, and, starting from her sleep, catches blindly at what first her newly opened eyes light upon.
In naturalism, characters are often governed by their base urges, no matter who they are. Naturalism takes the view of man as an animal only kept in check by civilization, ready to de-evolve should the wrong circumstances emerge.
Realism is less bleak in its outlook. In general, realism encompasses a wider range of fiction, not being as linked to a particular philosophy or time period as naturalism is. It simply tends to focus on everyday life without painting it with sentimental melodrama or romanticized gloss.
Henry James is one of the most prominent realist writers. He tended to avoid simplistic good versus evil in his work and strove to depict psychological realism in his characters. Daisy Miller is a great example of these elements. The characters in this novella have more free will than their naturalistic counterparts. Daisy is headstrong and willful. When she chooses to compromise her reputation and risk getting deadly yellow fever by staying out late with Giovanni, James does not make it appear she is being driven by nature or fate to her ultimate end:
“I am afraid,” said Winterbourne, “that you will not think Roman fever very pretty. This is the way people catch it. I wonder,” he added, turning to Giovanelli, “that you, a native Roman, should countenance such a terrible indiscretion.”
“Ah,” said the handsome native, “for myself I am not afraid.”
“Neither am I—for you! I am speaking for this young lady.”
Giovanelli lifted his well-shaped eyebrows and showed his brilliant teeth. But he took Winterbourne’s rebuke with docility. “I told the signorina it was a grave indiscretion, but when was the signorina ever prudent?”
“I never was sick, and I don’t mean to be!” the signorina [Daisy] declared. “I don’t look like much, but I’m healthy! I was bound to see the Colosseum by moonlight; I shouldn’t have wanted to go home without that; and we have had the most beautiful time, haven’t we, Mr. Giovanelli? If there has been any danger, Eugenio can give me some pills. He has got some splendid pills.”
“I should advise you,” said Winterbourne, “to drive home as fast as possible and take one!”
Unlike Trina, one does not get the sense that Daisy is destined to die. She dies because of her own impulsive choices regarding staying out late. She is not presented as a figure beneath a microscope, but as an elusive character the reader never fully comprehends, which is a defining feature of realism.