At the end of Chapter 23 of Harper Lee's To Kill a Mockingbird, Jem says that he understands Boo Radley better now. How has the trial helped him understand Boo?
In Chapter 23, Jem is very frustrated and confused about humanity after Tom Robinson is convicted for a crime he didn't commit. He's also been living with community members calling him and his family horrible names for the last year, while Aunt Alexandra talks about how honorable and valuable the Finch family is and has been to Maycomb county. It's all so confusing! Jem and Scout discuss what it all means: fine folks, gentle breeding, and what the difference and fuss is. Jem thinks that the difference between social classes in Maycomb comes down to who can read and write. Scout disagrees and says no one is any different than anyone else as far as that is concerned. Scout still doesn't quite understand the social caste system, but Jem is slowly figuring it out. He tells Scout the following after she says folks are just folks:
"That's what I thought, too. . . when I was your age. If there's just one kind of folks, why can't they get along with each other? If they're all alike, why do they go out of their way to despise each other? Scout, I think I'm beginning to understand something. I think I'm beginning to understand why Boo Radley's in the house all the time. . . it's because he wants to stay inside" (227).
Jem thinks now that Boo Radley stays inside because people are horrible to each other. There's no point socializing or being a part of a community that is made up of so many different people who can't respect each other. All of these different people living so closely together causes them to be mean to each other. There are power-struggles, gossip, hypocrisy, and prejudice between all different groups and classes in Maycomb. It's bound to drive a person crazy dealing with all of the intolerance. Jem figures that maybe Boo Radley has it all figured out, then. The way to stay out of all the drama from the community is not to be a part of it.
Jem is adamant that Tom is innocent. He doesn't see how the jury could possibly return a "guilty" verdict based on what he's seen at the trial. The fact that he's wrong totally shatters his faith in humanity. This connects with Boo in two ways. First, since Jem has lost his faith in humanity, he understands that maybe Boo is the smart one -- if society is capable of being so horrible to someone, why be a part of it? Second, Tom is innocent and he's wrongly targeted. Boo, as well, has many things said about him (monster, eating squirrels, lurking outside at night, stabbing parents with scissors) and he's innocent as well. Both Tom and Boo are connected throughout the novel, culminating in the symbolism of the title "To Kill a Mockingbird": both Tom and Boo are the mockingbirds of the novel.