Pride
Throughout this story, the narrator allows his pride to cloud his compassion and blind him to Doodle's limitations. He is too proud to accept having a disabled brother, and this is why he takes every measure he can to teach Doodle to do able-bodied things. Because of his pride, he does these things more with his own benefit in mind than his brother's. This story is a clear condemnation of blinding and debilitating pride, since the narrator's pride brings about the eventual death of Doodle.
Differences
Doodle is different from everyone else right from the start of the story, and the narrator has trouble accepting that. He cannot cope with the fact that Doodle does not fit with his image of a perfect younger sibling. When he pushes Doodle into learning physical skills, he threatens him with the thought of being different from everyone else when he starts school. But "different" does not necessarily have to be bad; Aunt Nicey is the one person who consistently claims that Doodle's differences make him special, not a pariah.
Recognizing Limits
It can often be tempting to push ourselves and the people we love past their limits in the hopes of achieving a goal, just like what happened with Doodle and the narrator. Sometimes this produces great results; after all, Doodle did learn to walk after working extremely hard. But it is important to be able to recognize when too much is just too much. The narrator was not able to see this, and he continued to push Doodle to his breaking point.
Family and Brotherhood
This story illustrates the importance of family bonds, particularly those between brothers. Doodle clearly looks up to the narrator, but many times over the course of the story the narrator fails to be the caring and compassionate brother he should be; instead, he is more concerned with the implications of having a disabled sibling. Without the support of his family or his brother, the person he looks up to most in the world, Doodle's strength was bound to leave him. At the end, following Doodle's death, the narrator realizes just how important his brother is to him, but by then it is far too late.
Guilt
Because this story is framed as a retrospective, there is a lot of room for the narrator's guilt to come through. The narrator flashes back to this time in his life with a wistful, guilt-ridden tone; it is clear he blames himself for Doodle's death, even though Doodle was extremely unhealthy to begin with and other factors came into play as well. Though readers are not given further information about the narrator's current life, they are left with the question of whether or not he will ever be able to overcome his guilt, move on, and be happy.
Appreciating Beauty
From the very first time the narrator takes Doodle to Old Woman Swamp, Doodle has an eye for all things beautiful. Natural beauty plays a huge role in this story, from the vivid descriptions of the house and its surroundings, the swamp, the storm, the creek, and so much more, right to the beauty of the fallen scarlet ibis itself. Both boys appreciate the beauty around them, but Doodle does especially; the natural world serves as a kind of therapy for him, a means of healing himself and moving forward in the face of his disability.
Breaking Expectations
Doodle's life, though short, was all about taking people by surprise and exceeding the expectations that others had for him. First, everyone believed that he would die, since caul babies usually do. Next, they believed that he would not be entirely sane because of his condition. Finally, they believed that he would never be able to walk. Every time, he proved them wrong. Even though Doodle ultimately could not overcome his physical limitations, his life was still an impressive story of beating the odds.
