In the novel The Catcher in the Rye, by JD Salinger, Holden has found enormous corruption and vulgarity in society. He knows that the children of the world are ruined by the corruption of adults around them. His newfound purpose in life will be to help save the children from this vulgarity by becoming a "Catcher in the Rye.".
In chapter 16 we have the first reference to the meaning of the novel's title, The Catcher in the Rye. Holden hears a little boy singing a verse, which makes Holden very happy: "If a body catch a body coming through the rye," Holden describes the little boy on page 115: "The kid was swell. He was walking in the street, instead of on the sidewalk, but right next to the curb. He was making out like he was walking a very straight line, the way kids do, and the whole time he kept singing and humming." Holden notes that the child's parents pay no attention to him. The little boy is in the road singing and his parents pay no attention to him? To Holden this child represents innocence and youth unspoiled by adult corruption.
Holden wishes to safeguard the innocence and purity of children, by protecting them from the evils of life. He feels that he has let Allie down; he wasn't there to protect Allie in his time of need. Holden now feels obligated to protect the rest of the children in the world. His little sister, Phoebe, asks him what he would like to be and he answers: "I keep picturing all these little kids playing some game in this big field of rye and all. Thousands of little kids, and nobody's around - nobody big, I mean - except me. And I'm standing on the edge of some crazy cliff. What I have to do, I have to catch everybody if they start to go over the cliff - I mean if they're running and they don't look where they're going I have to come out from somewhere and catch them. That's all I'd do all day. I'd just be the catcher in the rye and all. I know it's crazy, but that's the only thing I'd really like to be.