"Proof" is a play by David Auburn which won the 2001 Pulitzer Prize for Drama and the 2001 Tony Award for Best Play.
It was originally produced by the Manhattan Theatre Club and opened on Broadway on October 24, 2000 at the Walter Kerr Theatre.
It was directed by Daniel J. Sullivan, with Mary-Louise Parker as Catherine, Larry Bryggman as Robert, Ben Shenkman as Hal, and Johanna Day as Claire. Parker won the Tony Award for her performance.
Later during the Broadway run, Jennifer Jason Leigh and Anne Heche took over the lead role. Josh Hamilton and Neil Patrick Harris subsequently played the role of Hal.
The play concerns Catherine, the daughter of Robert, a recently deceased mathematical genius and professor at the University of Chicago. Claire has spent the last several years caring for Robert during a lengthy mental illness leading to his death.
Upon Robert's death, his ex-graduate student Hal discovers a paradigm-shifting proof about prime numbers in Robert's office. The title refers both to that proof and to the play's central question: Can Catherine prove the proof's authorship?
Along with proving the proof, the daughter also finds herself in a relationship with Hal. Throughout, the play explores Catherine's fear of following in her father's footsteps, both mathematically and mentally.