Proof was developed at George Street Playhouse in New Brunswick, New Jersey, during the 1999 Next Stage Series of new plays.
Throughout, the play explores Catherine's fear of following in her father's footsteps, both mathematically and mentally and her desperate attempts to stay in control.
Catherine complains that she hasn't done any worthwhile work in the field of mathematics, at least not to the same level as her father, a well-known math genius.
He reassures her that she can still do good work as long as she stops sleeping until noon and wasting time reading magazines.
He begins to comfort her but then alludes to a "bad sign" when he points out that he did, in fact, die a week ago.
In it, Robert writes it is a "good day" and thanks to Catherine for taking care of him and expresses hope for the future.
Catherine admits to calling the police the previous night and tries to explain her altercation with Hal but only ends up sounding unhinged to the dubious Claire.
Later that night, after the funeral, Claire holds a party in the house for her friends as well as Hal and Robert's students.
Catherine becomes enraged at the idea and she accuses Claire of abandoning her to take care of their sick father alone.
She blurts out that she has decided to go to college in a couple months, funded by Claire, but promises she will be only a short drive away if he were to need her again.
Robert assures him they will eventually work out the problem points together, then suddenly realizes he has forgotten Catherine's birthday.
Catherine shows Hal out and Robert sits down to write a notebook entry, declaring it to be the aforementioned "good day".
Resuming the end of the first act, Catherine declares she was the one who wrote the proof and is met with incredulity by both Hal and her sister.
The handwriting is very much like Robert's and Hal questions Catherine's mathematical abilities given that she only had a few months' education at Northwestern.
When Hal offers to show it to other math experts to confirm the authenticity of the proof, Catherine refuses.
She reads aloud, a nonsensical, rambling paragraph mathematically equating winter, books, and the cold.
*The film establishes their last name as "Llewellyn" (The name of a book publisher focused on topics of body, mind and spirit).
[1] Directed by Daniel J. Sullivan, the production starred Mary-Louise Parker as Catherine, Johanna Day as Claire, Larry Bryggman as Robert, and Ben Shenkman as Hal.
[2] Later during the Broadway run, Jennifer Jason Leigh (September 13, 2001 to June 30, 2002)[3] and Anne Heche (July 2, 2002 – January 5, 2003)[4] took over the lead role.
Josh Hamilton[5] and Neil Patrick Harris subsequently played the role of Hal.
Directed by John Madden, the cast starred Gwyneth Paltrow as Catherine, with Ronald Pickup as Robert, Sara Stewart as Claire, and Richard Coyle as Hal.
[6] Proof premiered in Australia at the Sydney Opera House in 2003, starring Jacqueline Mckenzie as Catherine, Christina Eliason as Claire, Barry Otto as Robert, and Jonny Pasvolsky as Hal.
[8] In April and May 2013, a new production by the Whitmore Eclectic Theater Group opened in Los Angeles at the Hayworth Theatre for a limited run.
[citation needed] In September to October 2013, Proof was directed by Emily Mann at the McCarter Theatre in Princeton, New Jersey.
[10] A Seattle production opened in January 2017 at Strawberry Theatre Workshop with three TPS Gregory Award-winning actors, Anastasia Higham, Charles Leggett, and Allison Standley in principal roles.
It featured Kelsey Brennan as Catherine, David Daniel as Robert, Nate Burger as Hal, and Laura Rook as Claire.
[12] A 2005 film adaptation was directed by John Madden, starring Gwyneth Paltrow as Catherine, along with Anthony Hopkins, Hope Davis, and Jake Gyllenhaal.
Adapted by Rebecca Miller, the film version added more characters (in minor supporting roles), whereas the play has only four.