Transcendentalism had become a major philosophical field of thought during the 1830s, and despite no less a figure than Ralph Waldo Emerson himself claiming that it had died out by the 1840s, it remained a strong influence on both culture and literature. Jack London's writings show signs of transcendentalist influence, and yet his works were set firmly in the realm of Realism, with little use for idealistic thought and behavior. "To Build a Fire" is especially significant in that it almost directly contradicts the ideas of man transcending animalistic instincts and growing to individual strength on the basis of intellectual and moral growth:
[The cold] did not lead him to meditate upon his frailty as a creature of temperature, and upon man's frailty in general, able only to live within certain narrow limits of heat and cold; and from there on it did not lead him to the conjectural field of immortality and man's place in the universe... Fifty degrees below zero was to him just precisely fifty degrees below zero. That there should be anything more to it than that was a thought that never entered his head.
(London, "To Build a Fire," jacklondons.net)
The unnamed protagonist is entirely rooted in The Real; the concepts of Man versus Nature never occur to him, and he makes the mistake of thinking that Nature must be malicious in order to harm him. In fact, it is the coincidental and unthinking aspects of Nature that cause his death. Instead of striving to make himself stronger than his human self by learning about the cold and taking steps to neutralize it, he simply walks into the wild and dies of hypothermia. There is no communion with nature, no epiphany of harmony, and the dog by his side doesn't even stay with him. In every sense, the story is rooted in Realism rather than Transcendentalism, and yet it works to reveal some of the essential flaws in that philosophy: man is not harmonious with Nature, but must be artificially protected from it, and to assume a spiritual or providential "right" to overcome Nature is to be willfully ignorant of natural dangers.