His silence is not only related to the fact that there is no one else to talk to, but also to the fact that talking is a human trait that is practiced in civilized society. Nick's sojourn to the heart of the country surrounding Seney removes him from civilization, so talking and engaging in practices that are appropriate for civilization are not appropriate where he is. The following quotation proves this point. "I've got a right to eat this kind of stuff, if I'm willing to carry it," Nick said. His voice sounded strange in the darkening woods. He did not speak again" (Hemingway). Nick's voice sounds odd due to his location, which is in a natural setting in the dark. The fact that he does not attempt to talk again shows that he realizes how inappropriate it is to engage in civilized practices when he is removed from civilization. From this perspective, then, it becomes clear that the natural setting has also triumphed over this particular aspect of civilization both externally in destroying the town, but also internally in silencing Nick.
Finally, Nick's solitude also is indicative of Hemingway's theme in this short story. Nick did not always travel, camp and fish alone; he recalls an incident that took place much earlier when he was in the company of two other men. Although a civilization undoubtedly consists of more than three men, even such a small group of people represents civilization in this story. However, the group splintered after one of the members, referred to as Hop Head, became rich. The following quotation indicates this fact. "The Hop Head was rich. He would get a yacht and they would all cruise along the north shore of Lake Superior. He was excited but serious. They said good-bye and all felt bad. It broke up the trip. They never saw Hopkins again" (Hemingway). Hopkins' sudden wealth represents the pinnacle of civilization in some ways. The fact that he no longer camps with Nick any longer that he is rich is suggestive of the incompatibility of money, and civilization with nature. Nick could have chosen to continue his expedition in the society of the third member of the group, but he does not. His preference for solitude shows that he prefers the solitude of nature over the civilization that his group represents; the fact that his group broke up because of civilization's influence demonstrates that nature and civilization are incompatible. Nick's preference to stay with nature, rather than civilization, is another triumph for the former over the latter.
Hemingway subtly informs the reader that the dominant them of "Big Two-Hearted River" is nature's superiority over civilization. He uses various elements of characterization and setting to prove this point. Ultimately, this theme represents nature's triumph over mankind itself.