Mark Cantan uses his mathematical skills to find the perfect formula for writing stage comedies

At a crucial moment in Jezebel, a brisk and tightly plotted new sex comedy by Mark Cantan, one of his characters considers the complications of a threesome and decides to do the maths. The probability that any given sex act involves a threesome, he determines, is 2.36 x 105. That means 2,834 menages-a-trois must take place a day. The further repercussions of this one – involving an uptight statistician, his businesswoman partner and a fretful naïf who arrives in their bedroom largely by accident – form the comic conceit at the centre of Rough Magic’s new production. It all sounds ridiculously unlikely. But “it was inevitable. When you think about it.”

Mark Cantan is precisely the kind of comedy writer who does think about it. Over the last few years he has emerged as someone who likes taking illogical situations to their amusingly logical conclusions. His 2010 play, The Get Together, another comedy of misunderstandings, contained more secrets and mix-ups than an avalanche of Alan Ayckbourn farces, to the point that one character had to recap them. “Dad thought Peter was my boyfriend, Mum and Tim thought Gary was my boyfriend, Dad thought Gary was Tim’s boyfriend, Mum thought Peter was Tim’s boyfriend, and Gary and Peter both thought each other was Tim’s boyfriend . . . Is that right?”

Beneath the pleasing construction and witty one-liners of Cantan’s comedy there’s an almost mathematical pleasure: every misunderstanding or embarrassment seems to obey an intricate algorithm. This isn’t accidental. Where some comedy writers start out as natural wits, sitcom nerds or gauche individuals drawn to stand-up, Cantan – like fellow number crunchers Tom Lehrer, Dimitri Martin or Dave Gorman – adds mathematics to the equation. He started writing comedy as a maths student in Trinity College Dublin during the late 1990s, performing in sketch shows heavily influenced by TV comedy and movie pastiches. His career since then, working alone or in collaboration for film, television and the stage (while more recently proving a dab hand at viral sketches on YouTube), has refined that combination, taking familiar set-ups and making their situations as complicated as possible.

“I always say that comedy is kind of about illogic,” he says. “It helps me to be a very logical person to work it all out in my mind. Maths is all a brain workout – if I move x over there, what would the next equation look like? – so to have that mental ability to juggle a few things in my head helps. I’ve also watched so many sitcoms and farces I know generally where they head. The challenge is to find new and original ways of making them.” In short, then, he seems fascinated by formulae.

That doesn’t make Cantan, whose conversation is peppered with references to Irish, British and American sitcoms, sound like a natural writer for the stage, where comedy rarely moves with the acceleration of the screen. “I don’t think I have the bravery yet to go five minutes without a joke,” he admits. Significantly, both The Get Together and Jezebel shift their locations constantly, some scenes lasting just seconds, while characters narrate their own actions. That can make Cantan’s scripts seem indifferent to the characteristics of the medium – and one could say the same thing about Cantan, a frequent theatregoer who, to put it mildly, is rarely impressed by what he sees.

“Yeah, I’m just not a big fan of Shakespeare.” Cough! Sputter! I’m sorry? “When you say that to people,” he continues, “they say, ‘You probably just haven’t seen good Shakespeare.’ But I’ve seen so much Shakespeare.”

As a participant on Rough Magic’s Seeds programme, a two-year mentoring scheme which involves frequent exposure to international theatre (and for which he wrote Jezebel), Cantan would often find himself alone in his dismay. “At the end of [Cheek by Jowl’s] Macbeth I thought, Thankfully I’m not going to be the only person who hated this. Everyone else was, ‘Oh my God, it’s amazing.’ I thought, Oh no. I’m in real trouble here.”

He was equally bewildered by an avant-garde production of Don Quixote in Warsaw. “By the end of it, I still didn’t know which one was Don Quixote.”

Cantan’s opinion is too considered to easily dismiss him as a philistine, although his arguments can be infuriating (The Usual Suspects has a better payoff than Macbeth; Dumb and Dumber is a funnier film today than Some Like It Hot). But he’s refreshingly candid about his views. “If there’s no story, or it’s not in a language I can understand, I can’t get something out of it.”

But Cantan does get something out of theatre, which, he points out, generates more instantaneous feedback than even a viral video. And it too could benefit from a writer who takes comedy seriously. “I don’t start out looking to raise issues,” he says. “I’m looking for what’s funny. And by finding new things that are funny it subliminally points out the foibles of society. Pretty much most comedies are about a breakdown in communication. Either people not understanding each other, not listening to each other, or lying to each other.”

He stops for a moment, as though computing. “I think,” he says. “Probably. I haven’t done a check on that.”

Jezebel runs at Project Arts Centre until December 22nd