Jack London set "To Build a Fire" in the times around the Klondike Gold Rush, when hundreds of individuals journeyed to the inhospitable North looking for their fortunes. London, having lived through some of those times and in some of those places, wrote the story partially as an indictment of the individualistic push to leave civilization for material wealth. The United States was still in the midst of its Industrial Boom, and living in a city rather than out alone on a farm was considered a proper goal in life. London's protagonist, by contrast, believes that he can survive the sub-zero temperatures with little more than his own will-power:
The old-timer had been very serious in laying down the law that no man must travel alone in the Klondike after fifty below. Well, here he was; he had had the accident; he was alone; and he had saved himself... All a man had to do was to keep his head, and he was all right. Any man who was a man could travel alone.
(London, "To Build a Fire," jacklondons.net)
This flies in the face of the individualistic philosophies that were popular at the time; although the individual was capable of great things, there are limits to human endurance, and the Klondike is an environment that pushes those limits and breaks them, without intention or malice. London's protagonist is too sure of himself; he is inspired by the many people who journeyed to the cold climates alone and returned wealthy, and believes that he is more intelligent than the "old-timer" who warned him. In that sense, the story is both informed by and aligned against the philosophies of an individual against the wilderness; London understood how dangerous the wilderness can be, and showed how even an intelligent man can be killed by improper preparation.