How the author uses Buck's character traits to develop a theme.

I would say that one of Buck's most prevalent trait is his loyalty. Buck is extremely loyal to Judge Miller and represents obedience to his master at the start of the work. Yet, throughout his being kidnapped and abused, he is exposed to the very worst of human action. It would make sense that he would completely distrust people throughout such an ordeal. However, he demonstrates the utmost of devotion and loyalty to Thornton, remaining with him and not fully going with the wolf pack. At the end, when Thornton is killed, Buck cuts off all ties with human beings, as exposed to the absolute cruelty humans can do. His loyalty is still present, when each year he visits Thornton's grave. The idea in Buck of loyalty and devotion to a higher good is evident throughout London's work.