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Holden Caulfield is an outsider because he has lost some of the optimism and insouciance of those youths who are his age. He simply does not relate well to some of his classmates or others.
In his introduction to his narration, Holden alludes to his brother D.B., who has gone to Hollywood as a writer. Holden feels that D.B. has become a "prostitute" because he does not write genuine books. In reference to his school, Holden narrates that he is not attending the football game. For one thing, the fencing team has ostracized him on his return to school because he left the equipment on the subway, an action that caused the team to have to forfeit the match. Another reason he does not go to the game is the fact that he has been expelled and he wants to say goodbye to his history teacher, Mr. Spencer, rather than be with his classmates.
Moreover, since his beloved brother Allie has died, Holden no longer engages in behavior that is as frivolous as that of other boys. Stradlater, his roommate, and Ackley, who has a room nearby, are of no interest to Holden because Ackley has certain physical traits that Holden finds repulsive, while Stradlater takes a girl that Holden really likes out on a date. This causes Holden to feel very alienated from him, especially when his roommate returns from his date and boasts, causing Holden to fight him.
Further in the narrative, Holden takes a friend, Sally Hayes, to see The Lunts, and she is excited about the play; however, at intermission, she angers Holden when she flirts with a pretentious boy from Andover, another school, and Holden is forced to listen to their "phony conversation." Still, he agrees later to take her iceskating. Holden then becomes angry with her when she wears a short skirt. When they sit down to rest, Holden begins to rant about all the "phonies":
The worst part was, the jerk had one of those very phony Ivy League voices, one of those very tired, snobby voices. He sounded just like a girl....
As he becomes more emotional, Holden asks Sally to run off with him and escape from society; however, Sally tells him he is being ridiculous and they quarrel. Holden tries to apologize, but his odd behavior angers Sally. Holden leaves without her, feeling alienated again.
Finally, in Chapter 24 Holden visits another former teacher, Mr. Antolini, his favorite teacher at Elkton Hills. He has admired Mr. Antolini for different reasons, one of which is Mr. Antolini's having carried James Castle's broken body to the infirmary.
Holden goes to Antolini's house because he feels that he can confide in his former teacher, but his visit makes him feel alienated, not comfortable. When he awakens shortly after falling asleep on the couch, Holden finds a drunken Mr. Antolini doing something that makes him very uncomfortable:
...he was sort of petting me or patting me on the ...head. Boy, I'll bet I jumped about a thousand feet.
Holden departs in disillusionment. Also, he certainly feels alienated from his former favorite teacher.
Suffering from teen angst and other troubling feelings, Holden feels himself at times to be outside the lives of others.
Holden throughout the novel neither is able to mix/ desolve himself up with the society he is in despite of different attempt nor does he can leave his ideology. he doesnot enjoy anything at all except the presence of Phoeb and Alley and Jane( who come in his memory) he is indifferent to almost everything around him. thus he can be conscidered outsider in this novel.