What can the reader infer about Lee's purpose of introducing Uncle Jack in chapter 9?
Uncle Jack is sort of a character who straddles both sides of the theme that ignorance and pre-judgement often lead to disaster. He is quick to punish Scout after she quarrels and fights with her cousin, without, as Scout puts it, "Hearing my side of the story." He is also quick to judge Scout regarding her cursing. The readers, of course, know the whole story: they know that Scout was provoked to the breaking point and they also know that Scout is a compassionate, thoughtful kid who will grow up to be just fine someday. Ultimately, Atticus explains the situation to Jack and puts his mind to rest. So, Jack is illustrative of that group of people in Maycomb, and the world, who almost have it right, but not quite. Or, they still need things spelled out to them in order to see things clearly. Jack serves as a kind of "everyman", a basically good person who still suffers from the same problem so many people in the world do: pre-judgement and not bothering to find out both sides of the story. This chapter also comes before the trial - when the idea that both sides of a story must be fully exposed in order for right action to be taken.