When Holden Caulfield sneaks into his family's apartment and visits his little sister Phoebe in Chapter 22, he tells her that he wants to be the "catcher in the rye," catching the children who run through a rye field as they reach a cliff, thus saving them. The precocious Phoebe corrects him about the poem by Robert Burns, explaining that the line is "If a body meet a body," not "if a body catch a body." Holden, who suffers greatly from the teen angst of facing the hypocrisies of adulthood, wants to believe it is otherwise in his desire to save the children and catch them, preventing them from falling into adulthood.
The ideas of catching and falling, then, become the central metaphor of the narrative that expresses a major theme of J. D. Salinger's novel, the agony of facing adulthood; for, the misinterpretation of Holden's as being the "catcher in the rye" identifies his desire to resist adulthood and its accompanying maturation and hypocrisies. As an instance of this theme, in Chapter 16, Holden reflects upon his visits to the Museum of Natural History where all the exhibits are fixed in time in contrast to Holden himself, who is different each time he has visited.
The best thing, though, in that museum was that everything always stayed right where it was. Nobody'd move. You could go there a hundred thousand times....Nobody'd be different.
The metaphor of "catcher in the rye" is equivalent to Holden's vision of life as one that may somehow be held fast and become manageable. He views childhood as a period of innocence and candor, such as Phoebe exhibits; on the other hand, adulthood is the cliff that one falls over. In the face of this disastrous plunge of adulthood admid hypocrisy and moral corruption, Holden finds his only defense to be running away and cynicism, both of which are, indeed, insufficient for dealing with life. There must be something, someone to catch and hold on to--not like his brother who has died--in order to find meaning in such a lonely and alienated world.