Here's what Scout learns about costume:
* Costume can be a form of disguise: Boo Radley's fear and paranoia lead him to avoid contact with the outside world. He hides himself, both physically and emotionally, through the use of clothing. He is described as wearing "old overalls and a raggedy shirt" and has a "disheveled" appearance. This costume helps him blend into the shadows and remain hidden from the community.
* Costume can be used for protection: Boo Radley's costume serves a protective function. It shields him from the judgment and fear of others. He is afraid of people, and his clothing acts as a barrier between him and the world.
* Costume can be a form of self-expression: Although Boo Radley is rarely seen, he uses his costume to express his own sense of identity. He chooses to wear clothes that reflect his isolation and his desire to stay hidden.
* Costume can be a way to hide one's true self: Boo Radley's costume helps him to hide his true nature. Scout learns that Boo is a kind and gentle soul, but his appearance leads others to fear him and make assumptions about him.
Scout's understanding of costume goes beyond just clothes. She learns that the entire town of Maycomb is involved in a sort of performance, wearing masks of prejudice and ignorance. This culminates in the trial of Tom Robinson, where the town puts on a show of justice that is actually rigged against him.
In conclusion, through Boo Radley and the events of the novel, Scout learns that costume is a complex and multifaceted concept. It can be used for disguise, protection, self-expression, and to hide one's true self. It can even be used to perpetuate harmful stereotypes and injustice.