Holden Caulfield is concerned about his sister, Phoebe, remaining a kid. He wants to ensure she will not be exposed to the phoniness of the world. To Holden, Phoebe symbolises the innocence and goodness of childhood and does not want her to be corrupted as he had been. When Holden is picking Phoebe up from school, he is appalled by the profanity written on the walls. He tries to rub the words off the wall but gives up after realizing he cannot clean all of them. Phoebe and Holden have a very close relationship. He feels the need to protect her since she is still a child. In Central Park, Holden becomes happy and relieved when he watches Phoebe ride the carousel since she is proving she is still a child.
Despite Holden's attempts to protect Phoebe, she has already been exposed to the cruelness of the adult world. She has most likely seen the profanity written in her school since it is everywhere. Additionally, Phoebe is already familiar with death and is grieving Allie.
[P1] Holden Caulfield wants his sister, Phoebe, to remain a child. [P2] Phoebe symbolizes youth and innocence. [P3] Holden wants to protect Phoebe's innocence. [P4] Therefore, the theme of The Catcher in the Rye is innocence and childhood.