How does inclusion of the dog's thoughts either reinforce or complicate the idea of nature as an indifferent force?no
The dog shows no real concern about the man. The animal is only concerned about its own welfare.
On the other hand, there was no keen intimacy between the dog and the man....It was not concerned in the welfare of the man; it was for its own sake that it yearned back toward the fire.
This dog is described as
...a big native husky, the proper wolf-dog, gray-coated and without any visible or temperamental difference from its brother, the wild wolf.
It is a part of nature and understands nature by instinct. When it understands that the man has frozen to death,
...it turned and trotted up the trail in the direction of the camp it knew, where were the other food-providers and fire-providers.
The indifference of the dog is London's way of representing the indifference of nature. Nature itself does not possess a consciousness, so the dog's thoughts, instincts, and feelings are an important element in this story. When it reaches the camp, the men who are keeping warm inside the cabin will recognize it and understand what happened to its owner.