What does Harper Lee, the author of To Kill a Mockingbird, think of the character Jem?
Although the story in To Kill a Mockingbird is told from the point of view of Jem's little sister Scout, Jem is one of the main characters in the book. The book is a coming-of-age story, not only about Scout, but about Jem as he learns to put himself in others' shoes, as he wrestles with the reality of injustice in his town, and as he learns to become a man of integrity like his father.
The book covers about three years of the children's lives. Jem is nine when the book opens, and almost thirteen when it closes. At the beginning of the book, Jem is fully a child. He eagerly believes ghost stories with Scout and Dill, he fears to approach Boo Radley's house, and he sees nothing wrong with playing a game that makes fun of Boo. Partway through the book, Jem starts to hit puberty. He gets taller, he becomes moody, and he no longer plays with Scout like he once did. He mulls over things a great deal more than Scout, and figures things out before she does.
One early example of this figuring out is in Chapter 8. Prior to Chapter 8, Jem has thought long and hard about the fact that Boo Radley fixed a pair of pants that Jem left in his yard, and that Boo had apparently been leaving little treasures in the old tree for Jem and Scout to find. But Jem has said nothing about any of this to his father.
Then in Chapter 8, Jem and Scout have been standing in front of the Radleys' house to watch a neighborhood fire. Later they find that someone has placed a blanket around Scout's shoulders. This is too much for Jem, and he begins telling his father all his worries about Boo:
Jem seemed to have lost his mind. He began pouring out our secrets right and left ... omitting nothing, knot-hole, pants and all.
"—he's crazy, I reckon, like they say, but Atticus, I swear to God he ain't ever harmed us, he ain't ever hurt us, he coulda cut my throat from ear to ear that night but he tried to mend my pants instead..."
At this point, Scout still feels a spooky fear of Boo Radley, but Jem has begun to realize that Boo is a human being who means them no harm. This is very cleverly done, since it is Jem's insight but is told from Scout's semi-comprehending point of view.
Another example of when Jem understands more than Scout, and feels more deeply, is during the trial. Scout faithfully reports all that was said during the trial, and she understands some of it, but Jem is hanging on every word, fully invested, making comments like "We've got him" when Atticus shows that Mr. Ewell is left-handed (Chapter 17). In Chapter 21, waiting for the jury's verdict, Jem is confident: "Don't fret, we've won it. Don't see how any jury could convict on what we heard." After the jury bring back their guilty verdict for Tom Robinson, Jem is shocked and crushed: "It ain't right. How could they do it, how could they do it?"
This is a turning point for Jem. The morning after the trial, Miss Maudie serves the children cake as she often does, but she serves Jem a piece from the big cake instead of baking a tiny cake for him, as if he is an adult now.
Later that day (Chapter 23), Jem and his father have a long conversation (which Scout overhears) about in what ways the system is broken and how it could possibly be fixed. Jem proposes we "do away with juries. He wasn't guilty in the first place and they said he was."
"If you had been on that jury, son, and eleven other boys like you, Tom would be a free man," said Atticus. "So far nothing in your life has interfered with your reasoning process."
So now we have Atticus's opinion (which is also Harper Lee's) that Jem is a boy of integrity, one who is learning to think clearly about the law and about life.