The four-line poem that begins the novel summarizes the essential theme of the entire work. As noted in the section at the end of this study guide, entitled "Critical Theories," we see that London is writing in a certain literary tradition and under the influence of a literary philosophy called Naturalism. The concepts of Naturalism are summarized in these first four opening lines — that is, within every individual, however civilized, there lies deep within a "ferine strain," which means that there is a "primitive beast" within each of us that can emerge at any particular moment, and it will emerge more quickly in periods of extreme stress. The "brumal sleep" refers to these forces that are hibernating and which will, at the proper moment, awaken and assume their bestial qualities.
In conjunction with the above ideas, London will use Buck, the enormous, extraordinarily powerful dog, as an anthropomorphic example of similar qualities for all of humankind. (Anthropomorphic simply means attributing human qualities to an animal.) For example, throughout the novel, Buck will be seen to possess various types of qualities that are traditionally attributed only to human beings. In one instance, we will see him possessing such qualities as loyalty, love, revenge, ambition, and other qualities usually associated with human beings. Other qualities will also be pointed out as we progress through the novel.
To emphasize his essential theme, London has the dog Buck being born on a large estate in the Southland (Santa Clara Valley, California). Buck does not know that there is a "yellow metal" recently discovered in the Far North and that strong, powerful dogs are desperately needed and will bring a rather large price. While Buck is a very large dog — his father was a huge Saint Bernard and his mother was a Scotch shepherd — Buck has lived a comfortable life of ease in very civilized surroundings. London writes that Buck "had lived the life of a sated aristocrat." Buck's master was the gentle and kind Judge Miller, the epitome of a highly civilized society. The fact that London chooses the Judge for Buck's master strongly underscores the fact that we are to be aware of civilization's laws, its customs, and all of the machinations of order.
