1. As London introduces the dog in the story, he writes that the dog "slinks" behind the man, not out in front as if eager to go on the journey. The author then goes on to describe the dog's instinct by writing,
"It experienced a vague but menacing apprehension that subdued it. . .and that made it question eagerly every unwonted movement of the man . . ."
2. When the man makes his fire for lunch and then puts it out afterwards, the dog wants to stay behind either by the fire or burrow under the snow until the cold subsides.
3. The man tries to make the dog go out in front of him to check for thin ice patches, but the dog knows better.
4. Finally, at the story's end, the man tries to kill the dog for warmth, but the dog wisely evades the man and then sits quietly until the man is dead. At that point, the dog instinctively heads to camp and warmth.
The evidence is everywhere. And evidence is not just of the dog's knowledge of the folly of the journey, it is the animal's instinctual fear of the danger of such an endeavor.
In this story, there are three elements: the man, the dog, and nature. The man is on a journey "bound for the old claim on the left fork of Henderson Creek;" the dog, nameless, accompanies him; and nature in this story is a vast, deadly cold wilderness.
"To Build a Fire" is built around the interaction of these three elements and each one is vitally important to the point: The man is a newcomer to these territories. Such newcomers even have a name; they are called "chechaquos." And worse for him, it is the dead of winter. Not only does he not know the lay of the land, he doesn't know the dire danger of the cold. The dog, however, knows the cold instinctually. It is the interplay between the supposedly intelligent man and the instinct of the beast that the story derives its meaning.
In the space remaining, I will highlight the some of the passages that deal with the dog's deeper knowledge of the imminent danger and not just the folly of the journey:
At the man's heels trotted a dog, a big native husky, the proper wolf dog, gray-coated and without any visible or temperamental difference from its brother, the wild wolf. The animal was depressed by the tremendous cold. It knew that it was no time for travelling. Its instinct told it a truer tale than was told to the man by the man's judgement.
The dog did not know anything about thermometers. Possibly in its brain there was no sharp consciousness of a condition of very cold such as was in the man's brain. But the brute had its instinct. It experienced a vague but menacing apprehension that subdued it and made it slink along at the man's heels, and that made it question eagerly every unwonted movement of the man as if expecting him to go into camp or to seek shelter somewhere and build a fire.
The dog dropped in again at his heels, with a tail drooping discouragement, as the man sung along the creek bed.
Once again, however, he had a close call; and once, suspecting danger, he compelled the dog to go on in front. The dog did not want to go. It hung back until the man shoved it forward, and then it went quickly across the white, unbroken surface.
The dog was disappointed and yearned back toward the fire. The man did not know cold. Possibly all the generations of his ancestry had been ignorant of cold, of real cold, of cold one hundred and seven degrees below freezing point. But the dog knew; all its ancestry knew, and it had inherited the knowledge. And it knew that it was not good to walk abroad in such fearful cold. It was the time to lie snug in a hole in the snow and wait for a curtain of cloud to be drawn across the face of outer space whence this cold came.
And all the while the dog sat and watched him, a certain yearning wistfulness in its eyes, for it looked upon him as the fire provider, and the fire was slow in coming.
It flattened its ears down at the sound of the man's voice, and its restless, hunching movements and liftings and shiftings of its forefeet became more pronounced; but it would not come to the man. He got on his hands and knees and crawled toward the dog. This unusual posture again excited suspicion, and the animal sidled mincingly away.
The evidence is manifest, for it is embedded in the meaning of this harrowing tale.