What important lesson did Buck learn from the man with the club in "The Call of the Wild"?
In chapter 1, Buck is kidnapped from Judge Miller’s peaceful estate in sunny California and brought to Seattle, where a stout man wearing a red sweater beats him into submission with a club. When Buck initially arrives in Seattle, he is enraged and vows to unleash his fury on the next human he encounters. Four men gingerly remove Buck's crate from the train car as he snarls fiercely inside his cage.
When Buck's cage is opened, he lunges at the man in the red sweater wielding a club and is violently struck to the ground. Buck attempts to charge at the man a dozen more times, only to be beaten back and smashed down by the club. Buck finally gives up and learns an important lesson, which serves as an "introduction to the reign of primitive law." In order to survive in the wild, the mightiest, most aggressive being reigns supreme and should not be challenged. Buck also learns to never challenge a man wielding a club.
Through the man with the club, Buck is introduced to "the reign of primitive law" (Chapter 1). This law says that "those with the greatest physical strength are the rulers" (enotes link referenced below). After being brutally beaten down time and again, Buck understands that he stands no chance against a man with a club. Such a man is "a law-giver, a master to be obeyed". A hierarchy is established, and although Buck's spirit remains unbowed, he knows he must submit if he is to survive (Chapter 1).