Which character serves as a pivotal influence on Buck's development?

John Thornton serves as a pivotal influence on Buck's development primarily because he represents the ideal of love and companionship in the harsh wilderness. Unlike the other characters Buck encounters, who often embody brutality and cruelty, Thornton displays kindness, loyalty, and compassion. This relationship profoundly changes Buck, allowing him to experience trust and affection, which he has been deprived of during his earlier experiences.

Under Thornton's care, Buck flourishes, becoming more confident and embracing his instincts. The bond they share restores Buck's faith in humans, contrasting sharply with his previous encounters, and serves as a catalyst for Buck's ultimate transformation. This mentor-mentee relationship is crucial in guiding Buck toward his true nature, leading him to discover his place within the wild and triggering his eventual return to a more primal existence. Thornton's nurturing allows Buck to balance his domesticated instincts with his wild heritage, highlighting the themes of loyalty, love, and the struggle for survival present in the novel.