#3: Did Catherine Write the Proof?

At the finale of the film, Proof, we are left to speculate on whether Catherine wrote the proof that was fought over by the characters. Looking back, we first come to find that the notebook in which the proof is written greatly resembled those of Robert, the great mathematician. As the movie progresses, we discover that Robert has given one of his notebook to Catherine, so she will get back to work and stop wasting her days. Hal, portrayed by Jake Gyllenhaal, seems to believe this is Robert's notebook and handwriting. Another factoid pitted against Catherine was the fact that her father was working again. With Robert's genius mind, it is hard to believe Catherine could compete with him.

Next, we come to find that Catherine has begun to write something. We are not sure what, but her and her father are both working on projects. Recalling that Robert and possibly Catherine are crazy from the beginning of the story, we cannot be sure what either of them are writing. As both characters finish their notes, Catherine begins to read her father's aloud. At this point in time, we discover Robert has written nonsense, and the fact that he can no longer work essentially kills him. Towards the end of the story, Hal discovers the handwriting is actually Catherine's and the style of math is newer than Robert's time. In the end, we discover that Catherine is not crazy, and she indeed wrote the revolutionary proof.