Jem Finch is brave, likable, idealistic and noble. In Harper Lee's novel "To Kill a Mockingbird," his younger sister Scout watches him grow and come of age over the course of three years. Initially, Jem's bravery manifests as a type of bravado, limited only to impressing his peers with daring acts. However, during the novel, he matures into a young man willing to stand up for his ideals.
Jem's maturity and strength of character is especially evident when he involves Atticus in Dill's runaway escape attempt. Scout and Dill both attempt to punish him by ignoring and excluding him, but Jem refuses to back down from what he feels is the right thing to do. His idealism is brutally confronted with the realities of the time when he learns the result of Tom Robinson's trial, his temper flaring to the forefront when he declares he would like to end juries forever. He also yells at Scout, unable to cope with his disappointment and his disillusionment with the legal system.
Interestingly, Jem's growth is seen through Scout's eyes as she witnesses his slow loss of innocence, one of the central themes of the novel. His compassion for Tom Robinson ultimately leads to him becoming a symbolic mirror of the man, as they are both injured by the same man.