Christopher’s defining characteristic is his inability to imagine the thoughts and feelings of other people. In other words, he cannot empathize. Because he cannot imagine what another person is thinking, he cannot tell when a person speaks sarcastically, or determine a person’s mood by his facial expression. This inability to empathize is one of the most prominent features of autism-related disorders, and this characteristic as well as a few others—Christopher’s difficulty understanding metaphors, his fixation on certain topics, and his computer-like ability with numbers—strongly suggest that Christopher has a mild form of autism. This condition has made him extraordinarily gifted in math and science but severely underequipped socially, leading Christopher to frequently misunderstand other people, especially his father. As a result, he greatly dislikes social interaction and avoids it when possible.
Although Christopher does not mention autism by name anywhere in the novel, we see that he recognizes the ways he differs from most people and feels keenly aware of these differences. He says, for instance, that although most people enjoy chatting, he hates it because he finds it pointless. He doesn’t see social interaction as an end in itself, thus talking to another person about an unimportant topic serves no purpose. He lives as an outsider as a result. He has very few friends and doesn’t trust other people. He feels content to read in his room by himself, and he even fantasizes about being the only person alive on the planet. Christopher also recognizes and takes pride in the strengths that result from his condition, such as his talent for math and his remarkably accurate memory. His memory allows him to recall an entire event in extraordinary detail, and he uses it to navigate social interactions by memorizing a chart of facial expressions and the emotions associated with them.
Christopher shows a growing desire for independence throughout the novel, and through much of the novel we watch as Christopher gains the confidence to assert himself. He shows his yearning for independence in a few ways, rebelling against his father by disobeying his orders, for instance, and fantasizing about doing whatever he likes and taking care of himself in his recurring dream of being one of the few people left on Earth. He also begins planning to go to college, and to live on his own there. As Christopher overcomes the various trials he faces, he gains confidence in his abilities and gradually becomes more self-sufficient. This process culminates in a difficult journey to London that Christopher undertakes by himself, a feat that represents a significant triumph for him since he has never traveled by himself. At the end of the novel, Christopher feels he has overcome his challenges, and he feels ready to be on his own.