Mathematics is at the centre of David Auburn’s Proof and so it's thus apt that The Oxford Theatre Guild’s adaptation, directed by Daniel Whitley, is being held under the corridors and offices of Oxford’s own Mathematical Institute. While the mysteries of number and logic are a preoccupation of those on stage, questions of talent, creativity, age, family, love, and madness take us away from the technical detail. It’s not just about proving a hypothesis, but also about proving oneself. Of course, real life does not enjoy the unambiguous rigours of the mathematical method.

Catherine (Kate Richards) has cared for her father Robert (Heward Simpson) in the midst of profound mental illness. Robert is known to be a great mathematician, but his grasp on reality is on a severe decline. Upon his death, Catherine sees herself following in her father’s footsteps – both in terms of his mathematical talent, but also potentially in terms of his madness.

As Catherine grows closer to one of Robert’s old prodigies, Hal (Marcus Davis-Orrom) and as her sister Claire (Laura O’Mahony) comes into town to haughtily help Catherine sort her life out, her grasp on reality – and on her work – is tested.

The play is a small, streamlined piece with well-developed characters. The worlds of these four individuals are deeply fleshed out, particularly Catherine, who deals with the pains of putting her life on hold to meet the needs of her father. Even Claire, a character who is comically irritating and yields most laughs, carefully avoids becoming a hollow stereotype.

The focus on characterisation is a true strength of Proof as is its ability to draw the audience in on questions of belief and reality. One heartbreaking scene flashes back to Robert in a period of relative mental stability. He talks about his growing clarity, his ability to think as he did in his twenties, and the possibilities his findings will have on the future of mathematics. The audience wants to get carried away with his delightful excitement, and yet knows also that his apparent lucidity is likely a grandiose symptom. It is a devastating experience to hear Catherine read his notebook aloud to reveal nonsense.

It seems a difficult feat to produce a play about maths which is fit for a general audience to follow along. But much in the vein of Good Will Hunting or A Beautiful Mind, Proof is captivating and clever, in an accessible way.