Holden Caulfield, as the main character in J. D. Salinger’s Catcher in the Rye, is struggling with his individuality (which we may think of as his identity). When we think about Holden’s individuality in the story, we must also look at the way in which he views and reacts to other people.
Over the course of the novel, we hear him call many other characters “phonies.” He repeats the word many times (according to one source it appears 35 times). His intent here is to show that these people are not “real” in some way—they are putting on an act, and this is something he just cannot stand. Someone like Holden, who is trying to formulate his own sense of self and individuality, does not have patience for people who hide their own true and unique identities.
At the same time, we must also consider the effect that Holden has on others. He drives away many of the characters in the story with his rude and sometimes hurtful observations—even his younger sister Phoebe, who he clearly adores and values.
So, Holden’s individuality is actually something of a burden; it turns into isolation because he is not able to forge mutually beneficial relationships with others. One way or another he will have to realize what he is doing and find a way to both grow as an individual and build positive relationships.
A topic sentence can be thought of as a main idea. If you could reduce your entire essay or paragraph down to one sentence, that would be your topic sentence.
Based on how I perceive the novel, a good topic sentence for a written response to a question about Holden’s individuality should mention that he is struggling to make sense of it (his individuality), but also driving away others, which is intensifying his sense of loneliness and isolation.