What finally forces Jem over the threshold into adulthood in Chapter 22?To Kill a Mockingbird by Harper Lee
After the trial of Tom Robinson in which there was convincing evidence that he was innocent, but the jury, nevertheless, has convicted him, Jem is extremely disturbed. For, his idealisitic concept of Maycomb as having "the best folks in the world" has been destroyed by the prejudice of Maycomb's jurymen. When he asks his father how such a conviction could occur, the fatigued Atticus replies that he does not know, but it has happened; Atticus, then, goes to bed.
The next day, the disgruntled Jem says little, only glaring bitterly when Calpurnia accuses Dill of being cynical, and making "feral noises" in response to seeing the town gossip Miss Stephanie on Miss Maudie's porch. But, Miss Maudie cuts short Miss Stephanie's accusations to Jem and Scout, inviting them in for cake. Once inside, Scout believes that Miss Maudie has forgotten to make a small cake for Dill; however, Miss Maudie gives Dill and Scout the two children's cakes and, instead, cuts a piece from the large cake for Jem, a gesture that symbolically indicates Jem's entry into adulthood for Miss Maudie. As she addresses Jem, Miss Maudie explains that others have also tried to help Tom Robinson: Judge Taylor chose Atticus rather than the new lawyer Maxwell Green, knowing that Atticus would do whatever possible to prove Tom's innocence, and Tom's friends have also done everything that they could. Cynically, Jem replies that no Christian judges and lawyers can "make up for heathen juries."
However, it is a more mature Jem who walks down the steps of Miss Maudie's house. For, when he hears Dill's declaration that he will become a clown so he can laugh his "head off," Jem replies that clowns are really sad and only the other people laugh. Then, when he sees Miss Rachel and Miss Stephanie waving wildly at them, Jem, who dislikes them, still tells the others, "I reckon it'd be ugly not to see 'em." Thus, to turn his own words said earlier in the narrative, Jem is "a gentleman just like Atticus."