Neighbors bring food with death and flowers with sickness and little things in between. Boo was our neighbor. He gave us two soap dolls, a broken watch and chain, a pair of good-luck pennies, and our lives. But neighbors give in return. We never put back into the tree what we took out of it; we had given him nothing, and it made me sad.
From this excerpt, Scout has learned that being a good neighbor involves giving. She discovers that a neighbor may have a "reputation", but that reputation is not all-encompassing. Boo gave to the children a token to his friendship and love (such as it was), despite the stories of his eating cats and looking in windows at night. Instead, he is a kindly man who cares for the children in his own way. From providing a blanket to Scout the night Miss Maudie's house burned, to saving Jem and Scout's life. Boo was not the monster that rumors meant him to be, nor was he a "normal" human being. Scout doesn't realize it, but she and Jem gave Boo someone to care for.
The first theme that I can think of relates to the wisdom of children, particularly Scout's wisdom when she confronts the lynch mob facing down her father at the steps of the jail. Scout is only a child, but her innocence is changed to an extent this summer as she sees the way that grown-ups behave. However, she retains enough childlike simplicity to make these men reconsider, for the moment, their actions. Atticus states in chapter 16:
So it took an eight-year-old child to bring 'em to their senses.... That proves something - that a gang of wild animals can be stopped, simply because they're still human. Hmp, maybe we need a police force of children.
Another moment in the piece that also relates to the wisdom of children is when Atticus emphasizes the imporyance of telling them the truth. He shelters Scout and Jem by protecting them, but he also is honest with them, for children have the wisdom to tell when adults are lying. He states in chapter 9:
When a child asks you something, answer him, for goodness' sake. But don't make a production of it. Children are children, but they can spot an evasion quicker than adults, and evasion simply muddles 'em