Bad Jews, Arts Theatre

Joshua Harmon’s provocative 2012 piece is the Rocky of comedies. His evenly matched sparring partners, a pair of viscerally antagonistic cousins confined in close quarters after a familial loss, bruise, bludgeon and literally draw blood. The bonds of kinship have never felt so tangible, so knotty, so inescapable.

Daphna (Jenna Augen) is aggressively committed to her Jewish heritage and lifestyle, while atheistic Liam (Ilan Goodman) all but disowns it, missing their grandfather Poppy’s funeral because he dropped his iPhone from a ski lift while in Aspen with gentile girlfriend Melody (Gina Bramhill). Liam has acquired – and plans to gift Melody – Poppy’s chai, a pendant of great personal significance; Daphna feels its religious and cultural symbolism means she is its rightful guardian. Liam’s brother Jonah (Joe Coen, pictured below with Ilan Goodman), called upon to act as casting vote during their hellish night in a cramped Manhattan studio apartment, clings to neutral ground as if it were a life raft.

Harmon and the excellent Augen and Goodman, under Michael Longhurst’s crisp direction, create a relationship steeped in history. This is just the latest salvo in a savage, ancient battle, each jibe and clash heightened by past damage. Intimate knowledge becomes ammunition in a bitter war on constructed personas, from Daphna’s teen cheerleader phase to Liam’s hated Hebrew name. Impressively, the taunts and tirades never render either assailant monstrous, with even the most vicious attacks strongly rooted in pain, fear, grief, and – most interestingly – self-criticism. Each works a little too hard to distance themselves from their counterpart. Yet they’re completely united in their unfiltered, bullying certainty.

Recent events colour Daphna’s assertion that Jewish culture is under threat from increasing globalisation, but Harmon’s taboo-busting play doesn’t stray too far into pure polemic. Commentary on selective faith, inherited suffering, racial purity and the weight of history is filtered through quick-witted, authentic personal drama, from Daphna’s clinical decimation of Melody to Liam’s unhinged, tour-de-force eruption. Bad Jews addresses global concerns, but it’s just as riveting in petty squabbles over an air mattress.

The conflict is sometimes gruellingly relentless, lessening its impact, though there are respites through lighter humour – including a memorably excruciating rendition of “Summertime” – and aching reflection. Poppy’s absence cuts deep, leaving three lost children to grow into the new heads of the family, while figuring out what that role means to them. Does honouring his memory, and their inheritance, mean rigidly adhering to tradition, or embracing the freedom to pursue their own paths?

Augen (pictured above left) is a revelation as abrasive, ferociously intelligent Daphna, whose pugnaciousness might be viewed differently if she were male, while Bramhill is a comic treat as her sweetly vapid polar opposite. Goodman smartly underlines the tension between Liam’s breezy preppiness and his simmering resentments, and Coen is a superb suffering straight man. Together, they offer a mesmerising take on the dysfunctional family (rivalling those game-players at the National) and a thought-provoking exploration of identity, universal in its razer-sharp specificity.

• Bad Jews is at the Arts Theatre until 30 May