In Harper Lee's To Kill a Mockingbird, the best way to determine the theme is to look at the things that Atticus says to his children. Atticus is presented as the wisest, most admirable character in the story, so it follows that his moral compass will point the reader toward the book’s central meaning. With that said, keep in mind that there are many ways to state a theme, and sometimes it is more a matter of opinion than anything else. Also, a story can certainly have more than one theme.
In chapter three, the narrator Scout has had a disappointing first day of school. When she gets home, she tells her father Atticus that she has decided not to go to school anymore; she’ll just stay home and learn from Atticus like she has been doing for the first six years of her life. Scout tells Atticus that the new teacher, Miss Caroline, has insisted that Scout no longer read with her father. This is something Scout cannot abide by. Atticus, the always patient and empathetic listener and observer responds with the lines that could well be considered the story’s theme:
"If you can learn a simple trick Scout, you’ll get along a lot better with all kinds of folks. You never really understand a person until you consider things from his point of view . . . until you climb into his skin and walk around in it.“
This quotation reveals an attitude that Atticus’s actions support throughout the story. As Scout and Jem grow older, they begin to understand what he means, and this affects how they live their lives. In fact, we can find evidence of this at the very end of the book, on the last page in fact. Jem and Scout have just been rescued from the murderous Bob Ewell by Boo Radley, the neighbor that they have failed to understand throughout the story. Scout’s observation about Boo reveals her character’s growth:
"Atticus, when they finally saw him . . . he was real nice."
Scout is now looking at things from Boo’s point of view, making an effort to see him for who he is and not as the monster that the children made him out to be.