gender and class intensify prejudice, silence the voices that might challenge the existing order, and greatly complicate many Americans' conception of the causes of racism and segregation." Lee's use of the middle-class narrative voice is a literary device that allows an intimacy with the reader, regardless of class or cultural background, and fosters a sense of nostalgia. Sharing Scout and Jem's perspective, the reader is allowed to engage in relationships with the conservative antebellum Mrs. Dubose; the lower-class Ewells, and the Cunninghams who are equally poor but behave in vastly different ways; the wealthy but ostracized Mr. Dolphus Raymond; and Calpurnia and other members of the black community. The children internalize Atticus' admonition not to judge someone until they have walked around in that person's skin, gaining a greater understanding of people's motives and behavior. Courage and compassion The novel has been noted for its poignant exploration of different forms of courage. Scout's impulsive inclination to fight students who insult Atticus reflects her attempt to stand up for him and defend him. Atticus is the moral center of the novel, however, and he teaches Jem one of the most significant lessons of courage. In a statement that both foreshadows Atticus' motivation for defending Tom Robinson and describes Mrs. Dubose, who is determined to break herself of a morphine addiction, Atticus tells Jem that courage is "when you're licked before you begin but you begin anyway and you see it through no matter what". Charles J. Shields, who wrote the first book-length biography of Harper Lee, offers the reason for the novel's enduring popularity and impact is that "its lessons of human dignity and respect for others remain fundamental and universal". Atticus' lesson to Scout that "you never really understand a person until you consider things from his point of view—until you climb around in his skin and walk around in it" exemplifies his compassion. She ponders the comment when listening to Mayella Ewell's testimony. When Mayella reacts with confusion to Atticus' question if she has any friends, Scout offers that she must be lonelier than Boo Radley. Having walked Boo home after he saves their lives, Scout stands on the Radley porch and considers the events of the previous three years from Boo's perspective. One writer remarks, "... [w]hile the novel concerns tragedy and injustice, heartache and loss, it also carries with it a strong sense [of] courage, compassion, and