relationship between the dog and the man reveals the man’s selfishness. At one point, when he senses thin ice that he could potentially fall through, the man pushes the dog ahead to test the surface. He would rather risk the dog’s life than risk his own. Later, after his attempts to make a second fire have been thwarted, he proves conclusively that he considers his own life more important than that of the dog. He plans to “kill the dog” and then warm his hands inside the body until they work well enough to make another fire. Luckily for the dog, he senses that something is wrong and stays out of the man’s reach.

The dog does not need any signs to know that being out in this weather is dangerous to the point of madness. He knows that fire is the best source of warmth, and as soon as the man builds the first fire when he stops for lunch, the dog tries to get as warm as possible.

In a nutshell, the dog knows the environment far better than his owner. When they leave that first fire, Jack London reiterates that the dog knows “it was not good to walk outside in such fearful cold.”

There is no doubt that when it comes to surviving out in the frozen wilderness, the dog is vastly superior to his owner in “To Build a Fire.” Whereas the man blunders into his near-suicidal expedition woefully unprepared, his canine companion senses from the outset that this is a dangerously hare-brained scheme.

For the time being, however, the dog stays with its master, if only for some much-needed warmth. And the dog will assist the man in his insane endeavors, even if it fears for its own safety. The dog knows that being out on the ice is incredibly dangerous, but he joins his human companion there anyway, albeit with extreme reluctance.

It's notable that when the man is fast approaching death, the dog immediately senses what's going on and instinctively recoils from him. The dog knows what's happening and what he must do when the inevitable happens.

After the man passes away, the dog's instinct for self-preservation goes up a notch and tells it to go find another human companion—someone else who can provide him the food and warmth that he desperately needs out here in the icy wasteland.

In outliving his hapless master, the dog has shown that when it comes to survival skills, animals are vastly superior to humans.

"To Build a Fire" is ultimately about the struggle for survival in the frigid conditions of the Yukon (in this sense, its primary conflict is one of man versus nature). The dog plays an important role within this thematic context, serving as a foil to the man, even as the two remain in an uneasy partnership that, in both cases, is driven by pragmatism and an interest in survival rather than by any genuine ties of companionship or affection.

For London, the dog, with its animal instincts, remains closely attuned to nature in a way that the man, still ingrained in the experience of civilization, cannot replicate. In this sense, seen within the struggle for survival against nature's overwhelming power, it is the dog that emerges as the man's superior. It is the man who is intent on trekking onwards through dangerously low temperatures (not realizing how severely cold it is), even as the dog's mind turns towards thoughts of warmth.

It is the man who makes the fatal mistakes in his determination to trek onward through these extreme conditions, and, moreover, in his arrogance to disregard all warnings and advice and attempt this journey alone. Meanwhile, it is the dog that retains an awareness of the extreme cold and the danger this represents. Indeed, this thematic contrast London paints between man and dog is perhaps most fully encapsulated in the story's ending, where the man dies and the dog goes on alone.

In Jack London's short story, "To Build a Fire", the man is a newcomer to the wildness of Alaska, and against all advice, he starts out for his camp alone except for his dog.  The man and the dog are essentially together because the man uses the dog as a tester for thin ice, and the dog stays with the man because he is the one who can provide fire and warmth.  The dog is forced onto the path as the tester for thin ice as the man cannot tell where he might break through into water, but the dog will break through for him.  The dog knows it is too cold to be out and is quite reluctant to be on the ice.  When the dog breaks through, the man builds a fire, eats his lunch, thaws out the dog, and then continues on.  The dog does not understand why the man would leave the warmth of the fire, but reluctantly leaves with the man.  When the man breaks through the ice and gets wet, he knows his life is in danger and tries to light a fire.  When that fails and the snow puts out his fire, he tries again but is too cold by now to control the matches.  Then he looks at the dog as a source of warmth if he kills it and crawls inside.  The dog senses the danger, and stays out of the man's reach.  The man finally sits down, realizes that he will die, and when he is dead, the dog heads out looking for another  man who will provide fire and warmth.  The relationship between the man and the dog is not personal, but purely the man using the dog to help himself and the dog staying with him because he can provide fire and warmth.  When that is gone, the dog leaves.