One of the novel's central themes is understanding what is real. At the outset, several of the characters repeatedly question what is real. Blajeny does so to teach his pupils that reality is not limited to what one knows or sees, whereas Meg asks it in disbelief of what she has seen and experienced. The concept of reality is something the characters must overcome if they are to fully understand the conflict with the Echthroi and the solutions for overcoming it.

Unfortunately, the human characters have difficulty coming to terms with a reality that does not align with their own. When Meg decides to take the cherubim to the elementary school, Proginoskes says “most earthlings can bear very little reality” (92). L’Engle illustrates this when Meg and Mr. Jenkins struggle to understand kything and Metron Ariston. These concepts are far outside their experience, so they have difficulty believing they are real. Blajeny’s and Proginoskes’ job is to help broaden their perspective to see that there is much more to reality than what they know. The characters begin to stretch their concept of reality, and once they do, they can fight and eventually defeat the Echthroi.