Every character in the novel has their own unique and complex interior life that other characters cannot perceive. Each character has a set of motivations, vulnerabilities, hopes and fears that are opaque to other people. The important simile used to describe this theme, raised early in the text by Simon as something that Blue wrote, is that people are like “houses with vast rooms and tiny windows” (18). In other words, there can be a great deal happening inside a human being, but it’s very difficult to see exactly what from the outside.

The difficulty of sharing this inner life with others is experienced as lonely and alienating, even for characters like Simon, who has a strong circle of friends and family. As someone who has not revealed their sexuality, Simon feels like there is a large part of his interior life he has not shared with those who love him. He can also appear frustrated by his inability to relate to other characters. When thinking about his younger sister’s motives, he admits, “I have a hard time getting into other people’s heads sometimes. It’s probably the worst thing about me” (41). Simon is initially curious about Blue because he writes about feeling lonely on the school’s Tumblr, a feeling Simon can relate to.