Jack London did not adhere to any particular philosophical or critical theories. Instead, he fluctuated from one critical view to another as the moment seemed to warrant it. Perfect proof of this statement lies in the fact that The Call of the Wild (1903) shows the Darwinian theories of the "survival of the fittest," as a dog is taken from its civilized Southland and is placed in the primitive North, where it must learn to cope with all sorts of primitive conditions if it is to survive. Then only three years later, London was to write the antithesis to this story in White Fang (1906), showing how a wild animal of the North (three-fourths wolf) who has been severely mistreated can, through a change in environment and proper attention, be changed into a civilized animal of the Southland.
When Jack London was born in 1876, Charles Darwin's theories of evolution dominated the scientific and theological world, and London utilized many of Darwin's theories in his writings. Essentially, this theory of evolution investigated the sources from which modern man developed and tried to describe how modern man was a result of a long period of evolution from other organisms (the most popular theory concerns the concept that somewhere back in time, both man and ape-like animals were descended from a common ancestor). During this process of evolution, all living things were subjected to a process known as "natural selection," which means that only those species which are the most adaptable to any given place or environment are able to survive. Accordingly, we have the concept of the ''survival of the fittest.'' This is one of the dominant concepts in The Call of the Wild and also in White Fang. For example, of all the dogs that are taken to the Great North, only Buck is able to make the transition completely — because he is the strongest and the most determined to survive. The instinct to survive is the strongest instinct known to man or animal. Likewise, in White Fang, the only cub of the five in the litter to survive is White Fang — again because of the survival of the fittest" theory and, by implication, the elimination of the weakest. Consequently, in these two novels and in other works by London, the idea of a struggle for survival among hostile or unknown forces is one of the dominant concepts found in the novels. The ability of the "animal" or "person" to adapt to new and different surroundings constitutes the essential plot of such novels.
Another concept which influenced London's writing was a method of writing called Naturalism. This involves both a technique and a way of viewing life. Essentially, the literary concept of Naturalism grew out of the concept of Realism during the latter part of the nineteenth century. The realist had wanted to "hold up a mirror to life" and to render a very accurate picture of life. The naturalist wanted to go a step further and examine life as a scientist would. Thus, the technique of the naturalist involves viewing life with scientific objectivity. Throughout his novels, London tries to depict his scenes in the great North with the objectivity of a scientist. He had personally been present in this Yukon country, and in scenes like the opening part of White Fang, he is able to capture the pure essence of the great frozen North, with all of its challenges to life.
More important, for the naturalist, man is controlled by basic urges, and he can do very little to determine his own destiny. Forces of environment, heredity, and biological instincts combine to control man's life. These basic and elemental urges place man in a position similar to that of animals. Consequently, according to the naturalist, man can, at any moment, resort to animal instinct or animal behavior, and thus London chose to write about animals, showing them resorting, at key times, to the primitive behavior that is in their own makeup.
A man or an animal born in one type of environment is influenced accordingly — to a point where the basic actions in his life are governed by these environmental forces. Carried to an extreme, this view of life leads to determinism — that is, the idea that man (or animal) can do nothing for himself or itself and is, therefore, at the mercy of forces outside of his own self. Consequently, White Fang and Buck are molded by their early environment and during the course of each novel, each dog has to change drastically in order to continue to function in a new and different environment.
Furthermore, man and animal are the victims of their elemental drives, which are, in turn, motivated by their environment, the biological need to survive, and by the hereditary traits of the characters. For example, when Buck is placed in the great North, his first instinct is to survive in this new and different environment. The biological need to survive influences the actions of both Buck and White Fang during the earliest parts of both novels. Likewise, the hereditary traits in Buck's makeup have lain dormant for generations, but during the course of the novel, he begins to hear the primitive "call of the wild," which arouses a deep instinctual urge in him and forces him, finally, to answer the various calls of the wild. As a result, he finally resorts to the primitive forces that have lain dormant in him. In contrast, White Fang is primitive, but because he possesses some part of the tame dog, the wolf part of his psyche is able to respond to human compassion and love, and thus he is able to finally function within a civilized society.