Answer:
The change in Amir’s character we see in the novel centers on his growth from a selfish child to a selfless adult. After allowing Hassan to be raped, Amir is not any happier. On the contrary, his guilt is relentless, and he recognizes his selfishness cost him his happiness rather than increasing it. Once Amir has married and established a career, only two things prevent his complete happiness: his guilt and his inability to have a child with Soraya. Sohrab, who acts as a substitute for Hassan to Amir, actually becomes a solution to both problems. Amir describes Sohrab as looking like a sacrificial lamb during his confrontation with Assef, but it is actually himself that Amir courageously sacrifices. In doing this, as Hassan once did for him, Amir redeems himself, which is why he feels relief even as Assef beats him. Amir also comes to see Sohrab as a substitute for the child he and Soraya cannot have, and as a self-sacrificing father figure to Sohrab, Amir assumes the roles of Baba and Hassan.
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