The notebooks are a symbol of Robert’s mental illness. He was a graphomaniac, writing compulsively and believing that he was continuing to do important work. Writing everything down while simultaneously losing one’s memory and mental faculties suggests an attempt to preserve what the afflicted person is losing. Catherine’s proof is not only a proof in the mathematical sense, but also in terms of evidence of Catherine’s ability to contribute to the field. When Hal finds Catherine’s notebook and believes that Robert wrote the proof, he says, “It means that during a time when everyone thought your dad was crazy… or barely functioning… he was doing some of the most important mathematics in the world” (47).

Similarly, Catherine wrote the proof during a period when she seemed to be barely functioning. She left school and seemed to be spending too much time in bed or reading trashy magazines. By writing in one of her father’s notebooks, Catherine shows a reluctance to own her work. Her life has not been her own, since she has been devoting it to caring for her father. Now that he is dead, Catherine is faced with the daunting responsibility of living her own life and trying to fulfill her potential.