Abandonment
Both David and the narrator suffer from immense fear of abandonment. The tragedy of their relationship, though, is that the narrator intentionally planted this fear in the boy's mind. Based upon his series of unsuccessful relationships, the narrator has assumed his own defectiveness and convinced himself that no one stays with him long if they can help it -- he's unlovable. Although this conclusion is necessarily one-sided and selfish, the narrator uses this belief to insulate himself from the consequences of his not-so-innocent relationship with David. Afraid that David too will grow up and leave him, the narrator carefully teaches the boy that everyone leaves and that his parents don't really love him and that he, the narrator, will be a father to him always.
When David leaves his home, he has no intention of permanently leaving. Upon his return, months later, he meets the new baby in his old home. Without even bothering to enter the house, David turns away. He has confirmed the suspicions which the narrator gave him about abandonment. David adopts a new identity as a lost boy, an orphan, having convinced himself that he is unlovable. Out of rebellion, he determines never to grow up.
Deception
Not only does the narrator lie to David, but he lies to himself as well. He falsely and prematurely concludes that something is wrong with him in order to cause all these people in his life to leave him. As a result, he believes that the only way to find relationship is through deception. The narrator tricks people into befriending him and then obligates them to stay. This strategy works with David because he's a child, without sufficient knowledge to understand how wrong the relationship is. With the mother and father, however, the narrator's immaturity betrays itself, and he cannot maintain the ruse through jealousy. Nevertheless, the narrator successfully indoctrinates David through deception and convinces the boy to live with him as a replacement father for the family who supposedly doesn't love him.
Aging
Since the narrator is concerned about aging, he projects this anxiety onto David as well. David starts to worry that his mom -- only 26 -- has already grown old. In a magical story, the narrator shows David a time previously when his mom was young and just getting to know David's dad. Through this tale, the narrator plants a further seed of doubt. He warns David that growing up makes people love you less. In order to remain loyal to this new friend, David is surreptitiously pressured to stay young -- a message he takes to heart by the end of the book.
