To Kill a Mockingbird is, at its heart, an examination of the ways in which innocence is impacted by society. Readers follow Scout and Jem as they journey away from the world of childhood ignorance and come to terms with the adult realities that surround them. Atticus’s decision to defend Tom Robinson initiates this loss of innocence, exposing the children to the ugly racism of their neighbors. Jem in particular struggles to cope with Tom’s conviction and the resulting realization that truth and goodness do not always triumph over lies. The trial serves as an awakening, not only for the children, but also for the town: just as the children must grow up and confront the adult world, the trial forces the town to confront its own deep prejudices.

While Scout and Jem's coming of age is a difficult transition, their loss of innocence leaves them more perceptive and sympathetic to the people around them. In the beginning of the novel, Scout and Jem are too naive to realize that their Boo Radley game might be hurtful. To them, Boo Radley is a “malevolent phantom”—a monster rather than a person. As their awareness of intolerance grows, the children come to see that Boo himself has been a victim of prejudice. Though Jem and Scout are both deeply affected by the events in Maycomb, Atticus’s guidance ensures that they emerge from their loss of innocence with their faith in humanity intact.

To Kill a Mockingbird also explores the ways in which the innocent may be unjustly injured by prejudice: racism denies Tom Robinson his legal innocence, while cruel rumors turn Boo Radley into a social pariah. Both Tom and Boo are living representations of the symbolic “mockingbird,” an innocent creature whose songs bring beauty to the world. Not only are Tom and Boo innocent of the accusations hurled against them, but they are fundamentally good people. Tom goes out of his way to help Mayella Ewell, whom he feels pity for, while Boo Radley braves the world outside his home to come to the aid Jem and Scout. Ultimately, the reader understands that just as Miss Maudie says it is “a sin to kill a mockingbird,” it is a terrible sin that the society of Maycomb has treated these two innocent men unjustly.