While Catherine doesn’t trust Hal with her sister, she does trust him with the proof. It’s not clear why Claire believes that Hal can be trusted with the notebook (and not claim it as his own). Perhaps it is because she noticed Hal’s dedication to giving Robert credit for his genius—his hours of reading the notebooks are evidence of his desire to publish Robert’s work. Or perhaps the play is suggesting that, in times of uncertainty, it is sometimes necessary to make a leap of faith in order to reach one’s goals. Claire, like Hal, wants to know who wrote the proof. In order to know, she has to trust someone else to analyze it—as she says, she isn’t mathematically talented enough to understand something as complex as the proof. Claire’s comment about her intelligence has another significance—it supports the play’s message that genius and mental instability are inextricable from each other. In Catherine and Claire’s family, one either has both or one has neither. While Catherine appears to have inherited Robert’s mental illness along with his brilliance, Claire got neither (or, at any rate, only a fraction of Robert’s talent).