In To Build a Fire, one theme is survival in the wilderness. The man who is traveling alone, except for his dog, is a newcomer to the region. He has no idea how cold it really is in the Klondike Wilderness. He is unprepared for the harsh cold that he is encountering. Even his dog knows it is too cold to be traveling. The theme revolves around the newcomer's first experiences in the extremely cold wilderness.
Early in the story, it becomes clear that the odds are against the man’s chances of surviving in the Klondike wilderness. He is a chechaquo, or newcomer to the region, and has never before experienced its extreme winters.
Another theme in this story is the individual versus nature. Nature is winning at the present. The newcomer wets his feet. He tries to build a fire and dry his socks and shoes. The snow from the trees falls on the fire, putting it out. The newcomer faces an angry side of nature. When the fire goes out, his chances for survival become slim. He must face the harshness of nature as a lone individual:
Yet during his trek the man is confronted again and again by his weakness as a lone individual against the formidable power of nature in the form of the brutal cold.
Another theme in the story is death. After the fire goes out, the man begins dying. He is freezing to death. If only the newcomer had listened to the old timer's advice. The man was warned not to travel alone, but he does so any way. Now, the odds are against him and the theme of death is a reality:
Once his fire is blotted out by snow and his body is threatened by hypothermia, the man must come to terms with death. His first reaction is to acknowledge calmly that the advice given to him by the old-timer was accurate: ‘‘If he had only had a trail-mate he would have been in no danger now.’’ This thought occurs to him again as he fails in his effort to rebuild the fire.
The theme of death is upon the man. He is dying. He will not survive. He must face the consequences for ignoring the old-timer's instructions. Nature ultimately wins and survival in the wilderness becomes impossible.