What role does innocence play in The Catcher in the Rye?

As its title indicates, the dominating theme of The Catcher in the Rye is the protection of innocence, especially of children. For most of the book, Holden sees this as a primary virtue. It is very closely related to his struggle against growing up. Holden's enemy is the adult world and the cruelty and artificiality that it entails. The people he admires all represent or protect innocence. He thinks of Jane Gallagher, for example, not as a maturing young woman but as the girl with whom he used to play checkers. He goes out of his way to tell us that he and Jane had no sexual relationship. Quite sweetly, they usually just held hands. Holden comforted Jane when she was distressed, and it bothers him that Jane may have been subjected to sexual advances from her drunken stepfather or from her date, Holden's roommate, Stradlater.
Holden's secret goal is to be "the catcher in the rye." In this metaphor, he envisions a field of rye standing by a dangerous cliff. Children play in the field with joy and abandon. If they should come too close to the edge of the cliff, however, Holden is there to catch them. His attitude seems to shift near the end of the novel when he realizes that Phoebe and other children must be allowed to "grab for the gold ring," to choose their own risks and take them, even though their attempts may be dangerous.