To Build a Fire Summary
A man travels in the Yukon (in Alaska) on an extremely cold morning with a husky wolf-dog. The cold does not faze the man, a newcomer to the Yukon, who plans to meet his friends by six o'clock at an old claim. As it grows colder, he realizes his unprotected cheekbones will freeze, but he does not pay it much attention. He walks along a creek trail, mindful of the dangerous, concealed springs; even getting wet feet on such a cold day is extremely dangerous. He stops for lunch and builds a fire.
The man continues on and, in a seemingly safe spot, falls through the snow and wets himself up to his shins. He curses his luck; starting a fire and drying his foot-gear will delay him at least an hour. His feet and fingers are numb, but he starts the fire. He remembers the old-timer from Sulphur Creek who had warned him that no man should travel in the Klondike alone when the temperature was fifty degrees below zero.
The man unties his icy moccasins, but before he can cut the frozen strings on them, clumps of snow from the spruce tree above fall down and snuff out the fire. Though building a fire in the open would have been wiser, it had been easier for the man to take twigs from the spruce tree and drop them directly below on to the fire. Each time he pulled a twig, he had slightly agitated the tree until, at this point, a bough high up had capsized its load of snow. It capsized lower boughs in turn until a small avalanche had blotted out the fire.
The man is scared, and sets himself to building a new fire, aware that he is already going to lose a few toes from frostbite. He gathers twigs and grasses. His fingers numb and nearly lifeless, he unsuccessfully attempts to light a match. He grabs all his matches--seventy--and lights them simultaneously, then sets fire to a piece of bark. He starts the fire, but in trying to protect it from pieces of moss, it soon goes out.
The man decides to kill the dog and puts his hands inside its warm body to restore his circulation. He calls out to the dog, but something fearful and strange in his voice frightens the dog. The dog finally comes forward and the man grabs it in his arms. But he cannot kill the dog, since he is unable to pull out his knife or even throttle the animal. He lets it go.
The man realizes that frostbite is now a less worrisome prospect than death. He panics and runs along the creek trail, trying to restore circulation, the dog at his heels. But his endurance gives out, and finally he falls and cannot rise. He fights against the thought of his body freezing, but it is too powerful a vision, and he runs again. He falls again, and makes one last panicked run and falls once more. He decides he should meet death in a more dignified manner. He imagines his friends finding his body tomorrow.
The man falls off into a comfortable sleep. The dog does not understand why the man is sitting in the snow like that without making a fire. As the night comes, it comes closer and detects death in the man's scent. It runs away in the direction of the camp, "where were the other food-providers and fire-providers."

About To Build a Fire
"To Build a Fire" is a prime example of the literary movement of naturalism. Naturalism was an offshoot of Charles Darwin's and Herbert Spencer's theories on evolution. In his monumental 1859 work Origin of the Species, Darwin theorized that environments alter the biology and behavior of organisms; the organisms whose traits promote survival reproduce more successfully and adapt new, more efficient traits. Spencer applied Darwin's ideas to the human environment, and Social Darwinism became one of the dominant philosophies in the late 19th century.
Naturalists saw evolution as proof that the world is deterministic and that humans do not have free will. Since the evolutionary world is based on a series of links (each of which causes the next), any action humans make is not, as we might otherwise believe, a "first" step. Rather, the action has been caused by prior environmental, social, and biological factors beyond our individual control.
This deterministic view influenced the naturalists in a number of philosophical areas. Since humans do not have free will, the naturalists refrained from making moral judgments on the actions of their characters; after all, the environment, and not the human, has determined these actions. The naturalists also viewed the deterministic environment as indifferent and harsh to its inhabitants; accordingly, keen instinct rather than civilized intellect is necessary for survival (in "To Build a Fire," the man is lacking this instinct).
Naturalists also changed their subjects and language to reflect their ideas. The lower classes were more conducive to depicting the harsh, indifferent environment, and in "To Build a Fire," the lower-class man is trying to strike it rich in the Klondike Gold Rush. Moreover, since the naturalists believed that the deterministic world could be understood only through scientific facts, their prose style was usually more journalistic and spare.
London journeyed to the Yukon Territory in 1897 along with countless others hoping to make a score in the gold rush. In November 1897, he staked a claim in Henderson Creek, the destination of the man in "To Build a Fire." Though he left Alaska the following summer without much gold, he would draw from his rich experiences in the northern wilds for many of his lasting works, including Call of the Wild and White Fang and, of course, 1908's "To Build a Fire," usually considered his most lasting work.

Character List
The man
The man in "To Build a Fire" is purposely not given a name, as the deterministic environment is more important than his free will and individuality. His goal at the start of the story is to reach the camp to meet "the boys," presumably to prospect for gold. The man's greatest deficiency, leading to his death, is his inability to think about the future consequences of present actions or facts; at the beginning of the story, London describes how the extreme cold does not make the man meditate upon mortality. More pertinently, the man does not realize that building a fire under a spruce tree may be dangerous. In all his actions, the man exercises only intellectuality--he thinks about the temperature in terms of degrees Fahrenheit, for instance, a scientific indicator. He never uses instinct, which would inform him without thinking that certain actions are dangerous. The dog, conversely, instinctively understands the danger of the cold without knowing what a thermometer is. Ultimately, the man's lack of free will exonerates him from any deep responsibility for the accidents he has, which is why London writes that the second accident was his "own fault or, rather, his mistake." A "fault" implies full responsibility, whereas a "mistake" suggests an isolated incident out of one's control.
The dog
The dog represents pure instinct, a trait necessary for survival in the harsh Yukon. Unlike the man, who requires the products of intellectual civilization--warm clothing, matches, maps, thermometers--the dog simply uses its own natural advantages--fur, a keen sense of smell. Perhaps more importantly, the dog has an instinctive understanding of the cold. It knows that such conditions are dangerous and unsuitable for traveling; when its feet get wet, it instinctively bites at the ice that forms between its toes. This sense of instinct preserves the dog as opposed to the man--it even knows instinctively when the man is attempting to kill it (to warm his hands in its carcass). Although the dog cannot create a fire for itself, or even hunt down food in the wild so well, its instinct keeps it alive and allows it to find the nearby camp of men--"the other food-providers and fire-providers."
The old-timer
The man remembers the advice of an old-timer from Sulphur Creek who warned him against traveling alone in the Yukon when the temperature is lower than fifty degrees below. The man first scoffs at this advice when he adeptly handles his first accident, but later understands the wisdom in the old-timer's caution: man is not instinctively fit for the harsh, indifferent environment of the Yukon.
The boys
The man is trying to meet "the boys" by six o'clock at night. Presumably, they are prospecting for gold. Though they never appear in the story, the boys (and the man) are examples of the lower-class characters naturalism turned its attention to; only men without much to lose would risk their lives in the harsh Yukon.

Major Themes
Determinism
The movement of naturalism was greatly influenced by the 19th-century ideas of Social Darwinism, which was in turn influenced by Charles Darwin's theories on evolution. Social Darwinism applied to the human environment the evolutionary concept that natural environments alter an organism's biological makeup over time through natural selection. Social Darwinists and naturalists cited this as proof that organisms, including humans, do not have free will, but are shaped, or determined, by their environment and biology. Naturalists argued that the deterministic world is based on a series of links, each of which causes the next (for more on these causal links, see Causal links and processes, below). In "To Build a Fire," London repeatedly shows how the man does not have free will and how nature has already mapped out his fate. Indeed, both times the man has an accident, London states "it happened," as if "it" were an inevitability of nature and that the man had played no role in "it." The most important feature of this deterministic philosophy is in the amorality and lack of responsibility attached to an individual's actions (see Amorality and responsibility, below).
Amorality and responsibility
A curious revision occurs when London writes that the man's second accident with the snow was his "own fault or, rather, his mistake." While both are damning words, "fault" is much more serious; it implies an underlying moral responsibility and role in future consequences, while "mistake" suggests an isolated incident outside of one's control. Likewise, the man believes his first accident is bad "luck," another word that connotes lack of free will. "Accident," too, insinuates an unforeseen or unanticipated event out of one's power.
If naturalism maintains that an individual has no free will (see Determinism, above), as London's careful phrasing suggests, then it is logical that the individual should not bear responsibility for his actions: if humans are not even in control of our own actions, why should we take responsibility for them?
The answer is that one should take responsibility for one's actions if one can anticipate potential consequences. Since the naturalistic world is based on causal links (see Causal links and processes, below), it should be possible, to an extent, to predict the consequences of our actions. The man could not have anticipated his falling through the snow, and therefore it is merely bad "luck." However, he should have anticipated that his other action--building a fire under a spruce tree--could carry potentially significant consequences: the snuffing out of the fire. Only in this anticipatory sense is he somewhat responsible. That London revises his judgment from "fault" to "mistake" suggests the gray area in the man's responsibility; while he should have anticipated the results of his actions, and thus be held liable, he did not, so he cannot be held liable.
Causal links and processes
"To Build a Fire" is, among other things, a virtual instruction manual on how to build a fire. It details specifically how one goes about gathering twigs and grasses, assembling them, lighting them, and keeping the fire going. The story, like many naturalist works, is obsessed with processes. These processes can be viewed as causal links--each event causes the next one. Causality is another preoccupation of naturalism, which grounds itself in the philosophy of determinism (see Determinism, above).
While the man in the story is adept with physical processes, he cannot make associative mental leaps and project causal links in his mind. London tells us this from the start, describing how the extreme cold does not make him meditate in successively larger circles on man's mortality. He has also ignored advice about avoiding the cold, not thinking ahead to what might happen in such harsh conditions. This deficit hurts him most when he builds the fire under the spruce tree; he does not think ahead that he might capsize the tree's load of snow and snuff out the fire. Only by the end of the story, when he is near death, does he mentally process causal links, thinking about his own death and how others might come across his body. The ability to process these mental causal links is the only way one can be held responsible for his actions in naturalism (see Amorality and responsibility, above). Since the man does not make these mental links, he is not fully responsible for the accidents that befall him.
Instinct over intellectualism
Though the man is hardly an "intellectual," he exercises intellectual properties more than instinctive ones. He uses complicated tools (matches) to build a fire; he understand how cold it is through temperature readings; he identifies where he is (Henderson Creek, the Yukon) through language on a map. The dog, on the other hand, is pure instinct. It remains warm through its fur coat or by burrowing into the snow; it has an innate understanding of the cold and its dangers; it could not point out its location on a map, but it knows by scent where to find the nearby camp with men. In the Yukon, instinct is far superior to intellect. The man's intellect backfires on him. His ability to light the matches with his numb fingers suffers in the extreme cold, and both his fingers and the matches are examples of man's naturally selected advantage of intellect: man has fingers to operate tools, and his larger, more complex brain allows him to create such tools. The dog is much wiser, aware that the cold is too dangerous for them; it even knows when the man is trying to deceive it somehow (he wants to kill it and bury his hands in its warm carcass). Accordingly, only the dog survives, and though it may not be able to take care of itself fully, it instinctively knows to go to "the other food-providers and fire-providers" in the nearby camp.
Indifferent environment and survival
Naturalism not only maintains that the environment is deterministic (see Determinism, above), but indifferent. The environment does nothing to help its inhabitants; in fact, it is coldly indifferent to their existence and struggle. In "To Build a Fire," the Yukon would be bitterly cold without the man, as well, and it does not cease when the man struggles to stay alive. This indifference makes survival itself a critical goal for naturalist characters. As the story goes on, the man changes his goal from reaching the camp, to warding off frostbite, to merely staying alive. Naturalism thus elicits profound conflicts, man versus nature being one of them.
The objective power of numbers and facts
Naturalism maintains that the world can be understood only through scientific, objective knowledge. In "To Build a Fire," the reader receives a number of these hard facts. For instance, temperatures lower than negative fifty degrees Fahrenheit demarcate the danger zone of traveling alone. London tells us the exact amount of matches the man lights at once (seventy). Moreover, the man is preoccupied with the distance to the camp and the time he will reach it. These hard facts should arm the man with enough information to assess competently the deterministic environment (see Determinism, above), but he fails to do so before he is in mortal danger.
Naturalistic subject matter and language
Naturalist fiction writers devised new techniques and subject matters to convey their ideas. Generally, they focused more on narrative rather than character. "To Build a Fire" has a nearly nonstop narrative drive, and we only occasionally enter into the mind of the man--who does not even have a name in the story, indicating how little London is concerned with him as a unique person. Naturalists often used sparer, harder language to complement their plot-driven stories; this tendency can be seen as a verbal corollary to naturalism's preoccupation with objectivity (see The objective power of numbers and facts, above). Finally, naturalism usually turned its attention to the often-ignored lower classes. The man in the story is a lower- to middle-class drifter trying to strike it rich; no one with any wealth would risk his life in such brutal conditions.