One of the unique features of London's novel is that he also writes about human instincts. Men like Francois, Perrault, John Thornton and his partners have shaken off the trappings of civilization, and London implies that this change allows them better access to their instincts. Consequently, they thrive on the trail, making it through multiple dangerous incidents because they trust their impulsive reactions. In contrast, Hal, Mercedes and Charles possess instincts, like all human beings, but they are so suffused with the notions of civilized life that they are unable to access them. London emphasizes the value of instincts, and he certainly presents their reassertion as a positive feature of a more natural, wilder lifestyle.