What was the inciting incident in the play Proof?

The "inciting incident" is the moment or occurrence that starts a problem in a work of literature or play (or in a movie). Up until that point, the audience has been introduced to the backstory, and the "inciting incident" brings up the dilemma that is going to be resolved in the rest of the work.

In the play Proof,the inciting incident takes place in Act I, Scene IV when Catherine, after kissing Hal, gives...

The "inciting incident" is the moment or occurrence that starts a problem in a work of literature or play (or in a movie). Up until that point, the audience has been introduced to the backstory, and the "inciting incident" brings up the dilemma that is going to be resolved in the rest of the work.

In the play Proof, the inciting incident takes place in Act I, Scene IV when Catherine, after kissing Hal, gives him the key to her father's desk. In the desk, Hal finds a proof, and he says, "It looks like it proves a theorem...a mathematical theorem about prime numbers, something mathematicians have been trying to prove since...since there were mathematicians, basically." Hal is not only excited about the proof because it is found after the death of Robert, Catherine's father and a famous mathematician, but also because the proof was written at a time when most people assumed Robert was far too mentally ill to be productive professionally. Just as the curtain drops to mark the end of Act I, Catherine says of the proof, "I didn't find it. I wrote it." This marks the inciting incident because there is no real proof that Catherine wrote the proof, pun intended.

Act II begins with a flashback to Robert and Catherine, and then, in Act II, Scene II, the plot continues to revolve around whether Catherine wrote the proof or not. Hal does not believe that Catherine had the capacity to write the proof, and Claire, Catherine's sister, thinks the handwriting in the proof is her father's. At the end of the play, Catherine says that even though Hal believes that the proof uses several new mathematical techniques that Robert, who was suffering from mental illness, couldn't have known, "it doesn't prove anything." Hal and Catherine begin working on the proof, collaborating, which is the greatest amount of proof Hal and the rest of the world are ever going to get that Catherine is the author of the proof. This process seems to resolve the questions that were brought up in the inciting incident to some degree.