David Edgar's new play Testing the Echo is named after something a visitor in Britain is not supposed to do: test the echo in one of the British Library's reading rooms. It epitomises many of the play's questions, not least of which is to do with what is acceptable in British society. Edgar challenges the mainly white, educated middle-class audience of the theatre to consider whether even we know the answer to this question.

The play is multi-stranded, and filled with a cacophony of different voices. The primary strand is probably that of Emma (Teresa Banham), an English language and culture teacher, who is teaching a class of recent immigrants how to be an English citizen, in order for them to pass a citizenship test. However, the class awakens prejudices that Emma, usually a progressive liberal left-of-centre thinker, didn't think she had. Clinging on to this main narrative are all kinds of stories featuring a cast of characters from a fundamental Muslim, an Eastern European construction worker, an unhappy Ukrainian housewife and a set of white, middle-class dinner party guests.

All David Edgar needs is the kitchen sink, and he'll be set. The benefit of having such a scattershot approach is that the play is in a constant state of debate and shift; the arguments presented are increasingly complicated by another voice and opinion. The audience is left with a tangled web and very few answers. Although Edgar does make it clear that he is firmly on the left and for freedom of speech, he carefully presents all aspects of the argument and leaves the ultimate decisions to the audience. It's startlingly even-handed, perhaps even uncomfortably so.

The production is perhaps a little bit staid in its presentation. There is an abundance of chairs and posing throughout, which can occasionally be off-putting. Fortunately, the level of acting is quite high, so any accusations of sixth-form drama class are pretty much quashed by the play's end. The direction's earnest pandering to the audience is actually quite endearing after a while.

While being far from perfect, this is as close to a theatrical event as Oxford gets. It's a scorchingly relevant major new play by an important playwright, and anybody with an interest in contemporary drama owes themselves to go and see this as soon as possible. It continues at the Oxford Playhouse until tomorrow.