The reader never knows exactly what is going on in Shawn's father's head since the novel is not written from his point of view. The only clues we have are those that Shawn has: at first, it seems to Shawn that his father wants the best for him, but Shawn gradually realizes that his father genuinely believes he is better off dead. Shawn's father is unsure of whether Shawn has any mental capacity at all, and he worries that Shawn only has the capacity to feel pain. In that way, Shawn's father only views him as an object, not as a person. Shawn is completely immobile and unable to communicate his thoughts, desires, joys and pains. In that way Shawn is almost like a pet and not like a child.
The first person limited point of view creates the tension, irony, and meaning of this story. Just as Shawn’s father can only guess what his son’s internal life might be like, so Shawn must interpret through his father’s actions whether he really does plan to end Shawn’s life. An interesting exercise would be to rewrite this story from the first person limited point of view of Shawn’s father, keeping in mind that he moved out when Shawn was three years old because the child’s seizures were more than he could handle, and also that he is a creative man, winning a Pulitzer Prize for a poem based on his experiences as parent to a victim of cerebral palsy. Another interesting exercise would be to write what you think Shawn’s father would write in his journal, a book that no one would read by himself. Both of these writing projects would help you understand the father from this point of view rather than that of his son, every bit as brilliant and creative as he. The strength of the novel lies in the father-son dynamic; the delicate scenes between them carefully illustrate their mutual quest to understand each other.
The theme of the story is that Shawn is a complete human being, but his father doesn't see him as a person, so he doesn't think of Shawn in those terms. He sees Shawn as his sick son who isn't able to speak, who suffers terrible seizures, and who is suffering from the horrible disease of cerebral palsy. It's because of Shawn's inability to communicate that his father has to draw his own conclusions about how Shawn feels. His father thinks Shawn has no quality to his life, not realizing Shawn sees, hears, and reacts to his environment. He thinks Shawn would be better off dead because all he does is suffer with no joy in his life.
Although Shawn's father loves him, I don't think he has any idea of what his son is like as a person. The story, written from Shawn's viewpoint, reveals him to be an intelligent individual with thoughts, feelings, and attitudes similar to any other boy his age, but he has no way of communicating this to the outside world. All Shawn's father sees is a terribly damaged child who has no control over his body and who suffers regularly from seizures which appear to be extremely painful. Because of this, Shawn's father struggles, out of love, over the idea that Shawn might be better off dead, so that he won't have to suffer anymore. Shawn does not agree with this idea at all, but cannot make his feelings known.