Naturalism is realism taken to its natural and logical extremes. Realism was a radical change from the fantasy stories of the past with magic and religion coming together with the power of love and dreams along with the supernatural and mysticism of the early 1800’s with gothic romances such as Frankenstein or Dracula or Picture of Dorian Grey. It is taking everything only for its realistic and non-supernatural values. Realism is going through the lives of ordinary people with less of a focus on them, with them being more of the stepping stone of the reader to realize the beauty of nature and its descriptions.
Naturalism is this taken to its own logical conclusion. Naturalism is the combination of all of those along with the nihilistic feeling of human inferiority that came from the massive public realization that maybe we weren’t specifically made by a God, that maybe we did just fight nature and evolve into what we were and the insignificance that came along with it. Naturalism is realism but with the added description of human futility and the nihilistic lovecraftian sense that we can not control nature in any way and nature can be the most harmful thing to man.
That is the point of the famous naturalistic story “To Build a Fire” which talks about a man's journey through the cold and heartless Yukon territory. First, let us prove its tendencies of realism which it shows by its lack of description of the main character, known only as the man, with no description of his appearance or backstory other than he’s searching for gold and he is new and he chews tobacco. The next big indicator is that it scenery chews throughout the entire short story with parts such as “the Yukon lay a mile wide and hidden under three feet of ice. On top of this ice were as many feet of snow. It was all pure white, rolling in gentle undulations where the ice-jams of the freeze-up had formed. North and south, as far as his eye could see, it was unbroken white, save for a dark hair-line that curved and twisted from around the spruce-covered island to the south, and that curved and twisted away into the north, where it disappeared behind another spruce-covered island.”
Now that we have the realism tendencies sorted out, let us go into the dark pessimism that drives it into naturalism; and that would be biggest about the fact that the man dies of frostbite, succumbing to the elements at the end. But the biggest part of that pessimism at the end is the fact that the dog, who has accompanied him loyally throughout the entire journey, after he died “turned and trotted up the trail in the direction of the camp it knew, where were the other food-providers and fire-providers,” showing the nature of the dog did not care for the amn specifically for any reason or even care for him. Which shows the lack of compasssion for humans by the elements and animals. Which is the central theme of Naturalism.