In chapter 15 of "To Kill a Mockingbird," what does the mob scene tell us about the nature of humans and how they behave?
How does Mr. Underwood's actions at the end of the chapter also tell us about the nature of humans?
Atticus tells Jem in the following chapter to remember that mobs are "made up of people", meaning that if a mob is broken down into the idividuals that are part of it, then it is no longer a mob thinking with the emotional collective brain. It is now just a group of individuals each with his own sense of right and wrong. There's a reason why we have the term, "mob mentality" and that is exactly what is displayed in that scene in ch. 15. Scout, by addressing Mr. Cunningham reduced the mob to individuals. People, on their own, are far less apt to do the things that mobs do. Mobs tend to rely on emotion and not thought, whereas people are more likely to use some thought before they act. This is the lesson that Harper Lee exhibits with this scene. The scene with Mr. Underwood tells us that even people who disagree on some issues can stand up for one another and protect one another. Mr. Underwood is not known around Maycomb to be the type of person typically to stand up for others, but he is shown having Atticus's back the night the mob came to the jail.
It tells us first that people will act differently as part of a mob. They lose their individuality and adopt a mob mentality. By doing this an individual that is part of a mob will act differently than they would on their own.
However, Scout is able to diffuse the mob's anger by reminding one member, Mr. Cunningham, of his individuality. As Atticus states in Ch. 16, "A mob's always made up of people, no matter what, Mr. Cunningham was part of a mob last night, but he was still a man" (157). It takes Scout reminding Cunningham that he is a father (his son is in Scout's grade) as well as a citizen of Maycomb county (Atticus helped him with some legal troubles) to break him out of his mob mentality. Again, as Atticus states, "So it took an eight-year-old child to bring 'em to their senses" (157).
Humans also have a tendency to dehumanize their victims. When the mob shows up to lynch Robinson, they don't see Atticus as a man, father, and (often) their ally. Scout is able to make Cunningham see Atticus as man and not just an obstacle in their way.
Underwood's presence at the end of the chapter might reveal that people will try to do the right thing despite their personal beliefs. Underwood dislikes African Americans, yet he has Atticus covered. Underwood could have turned a blind eye and allowed the mob to lynch Robinson (it is doubtful that Atticus could have done much to stop them). But he did the right thing.