Chapter 23 of To Kill a Mockingbird involves a long and thoughtful conversation in the Finch house concerning the nature of justice and the events of the recent trial. When Atticus tells his family that it was a cousin of Walter Cunningham who kept the jury from immediately convicting Tom Robinson, Scout says that she wants to invite Walter Jr. over for dinner once school starts. Aunt Alexandra rebuffs this idea, claiming that the Cunninghams are too low class to come to their home and would be a bad influence on Scout.
In his bedroom, Jem tries to console his sister, who is very upset at her aunt's assessment of the Cunninghams. Jem says that he has figured out that there "are four kinds of folks in this world." He divides people up into ordinary folks, folks like the Ewells, those like the Cunninghams, and "the Black folks."
This assessment does not satisfy Scout. Through her own experience and the lessons she learned from her father, Scout sees a common humanity between all people. To her, all people are simply "folks." Jem is frustrated that his little sister doesn't accept his analysis and dismisses her reasoning as childish.
This section illustrates how the Finch children are thinking more deeply about issues of prejudice and social divisions. The different conclusions that they come to are representative of larger elements of society that are at odds with each other. Some people, like Jem, want to classify people into easy to identify groups. They may view this as a pragmatic approach. Meanwhile, others like Scout, see this as prejudicial and strive to see everyone as part of a common humanity. At any rate, we can see that Scout's opinions of other people have changed significantly since Walter Jr. came to the Finch house for lunch the previous year.