The plot revolves around a monumental mathematical genius, Robert (Bill Van Horn), whose beautiful mind snapped years ago; when the play opens, he's already dead. His younger daughter, Catherine (Alex Keiper), who inherited his talent and may have inherited his madness, sacrificed her life and education to care for him. Her older sister, Claire (Krista Apple), turns up for the funeral, and his former grad student protege, Hal (David Raphaely), now a math professor himself, is going through the notebooks his mentor left behind. When he discovers a final notebook containing a groundbreaking elegant proof, the plot turns.
Catherine tells Hal about Sophie Germain, an 18th-century French mathematician who discovered what are now called Germain Primes, a kind of prime number; her story is emblematic of the place of women in higher mathematics, not just in the 18th century, either, and a significant signal in the plot of Proof.
The title of the play resonates in several ways: Mathematically, a proof is of a theorem, a series of formal statements showing that one assertion necessarily leads to the next. This kind of proof is hard. Proof, as we generally use the word, is the result of evidence, making it much easier than trust. And Proof is, finally, about trust as well as a proof and the lack of proof about the proof.
All the performances are tender and subtle and absolutely convincing. The lovely set - a brick wall, old porch furniture, dried leaves caught in the window screens - is designed by Andrew Thompson, and the lighting, designed by J. Dominic Chacon, is full of charm and significance as night turns to dawn and then morning light breaks.
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