This Is Good Advice: This Is A Chair by Caryl Churchill, Advice to Iraqi Women by Martin Crimp, directed by Lauren Barnes. Sound design by Rueben Stanton, set design by Rhys Auteri and Vlad Mijic, set illustrations by Vlad Mijic and Harriet O'Donnell. Welcome Stranger @ Trades Hall, Carlton, until February 10.

Sometimes the concept of "British Political Theatre" seems synonymous with David Hare, whom the SMH describes this week as "Britain's most committed left-wing playwright". I'm not sure how one measures such things, but in a field that includes barnacled warriors like Edward Bond or Harold Pinter, this seems, to say the least, highly arguable. Hare takes the prize - in the mass media, at least - because he writes about issues that everybody recognises as politics, from Israel to Iraq, in ways that are utterly familiar to anyone who has watched television. Hare's finger, it seems, is ever sensitively pressed to the pulse of current affairs.

But Britain has produced deeply committed political playwrights whose artistic achievements far overshadow the narrow oeuvre of David Hare. Caryl Churchill is among the first rank of these. Since the early 1960s, she has steadily written plays that express her commitment to socialist and feminist ideals and, later, a disturbingly prescient vision of a natural world being destroyed by the relentless progress of global capitalism. She is also one of the most exciting formalists now writing in the theatre.

This Is A Chair is a case in point. This short and elegant play, premiered by the Royal Court in 1997, is a sardonic evolution of Bertolt Brecht's Fear And Misery of the Third Reich, a series of fragmentary and realistic sketches of the impact of Nazism on the ordinary lives of Germans. Brecht's examination of the nexus between politics and social behaviour is at once oblique and direct, focusing on the apparently inconsequential to illustrate the rapid erosion of rights and freedoms under Hitler's regime.

Churchill has shaved this form to the bone; at first sight, her sketches of mundane social interaction have nothing to do with their purported titles - War in Bosnia, The Northern Ireland Peace Process, Genetic Engineering. They are at once domestic and strangely iconic: a young woman stands up a man with whom she has a date, a couple order their child to "eat up", two old women watch television while discussing a medical procedure. The only overt sign that something else is going on - in the text, at least - is in the scene titles, which, in classic Brechtian fashion, are to be displayed or announced before each scene.

The cognitive dissociation that vibrates between the labelling of significant public events of the mid-90s and the brief sketches that supposedly illustrate them has an effect that becomes progressively more and more uneasy. One hunts for the connections, and finds more usually a disconnection. What comes closer and closer to the surface is the carelessness people display towards each other in their ordinary lives, an ethical callousness that might appear minor and unimportant, but which, in the magnification of the theatre, demonstrates how little people actually perceive each other's pain.

The amplification from the micro to the macro is not a simple question of metaphor, of these domestic mise en scenes illustrating in miniature the larger public events. Rather, Churchill is sketching out an ecology of human affairs, creating a sense of how these small events accumulate into a social ethos. Just as climate change is created by billions of individually insignificant choices, so a callous public ethos is linked to countless smaller events, such as a doctor persuading an old woman not to use anaesthetic during a procedure in order to save money. In each case, the capacity of empathetic responsibility - one of the better human traits - is imperceptibly worn away.

More, Churchill is playing with the nature of knowledge and its relation to reality. The statement "This is a chair" is a common philosophical cue for investigating knowledge: how we know things, whether they exist apart from our knowing of them, what the nature of this knowing is, what role language plays in constituting human realities, and so on. These are the kinds of questions at play, as the program points out, in Magritte's famous painting Ceci n'est pas une pipe (This is not a pipe). All the same, I can't escape a nagging suspicion that Churchill is also employing a playwright's direct literalism in her titling: an insistence that, indeed, things are as they are seen, which is not at all the same as how they are said to be.

It's a subtle thesis which is largely trampled by Lauren Barnes' production for Welcome Stranger, although she makes a creditable attempt at what is an extremely challenging play. Only a writer of Churchill's calibre and precision could even attempt such a stylistic coup, and the demands of this kind of spare text are unforgiving to even the most experienced actors. The actors employ blackboards, emphasising an pedagogic element that might exist in Brecht's play, but which in Churchill's remains ambiguous: it is not a lesson play, a Lehrstücke, so much as an attempt to destabilise the simple categorisations that make it easy for us, in our media-driven age, to ignore the actualities of our actions.

So what is written as a simple interaction is labelled for us: the opening scene, for example, has blackboards behind each actor: He is Bosnia, She is Britain. (I confess, I was at first confused: I thought they had just got their grammar mixed up, not that they were different nations). The effect is to simplify its complexities, to read the play in a directed way that removes much of its jangling affect. In order to play with a proper metaphorical potency, a text of this kind requires an intensity of realism in the performance which is here side-stepped by the approach: the subtext is, as it were, written out for us, and I'm not certain that it's the correct subtext.

All the same, there is enough ingenuity in this simple staging and enough energy in the performances to keep it interesting. It's not surprising that the lesser play - Martin Crimp's 10 minute Advice to Iraqi Women - is by far the more successful piece. Here the actors are working well within their limitations, and Crimp's piece, which depends - albeit in a far less nuanced way - on an ironic dissonance between its text and its content, finds the comedy and depth that eludes the earlier piece.

Advice to Iraqi Women is a litany of the advice routinely given out to mothers to ensure the safety of their children - always supervise children near water, lock away poisons, give them good food. It has long irritated me that such advice is couched in terms that feed parental paranoia, thus no doubt ensuring that we are the most protective parents in history. (Yes, I am all for sensible safety standards...) Crimp picks up on this rhetoric to create what becomes a blackly ironic comment on the hypocrisy of the British Government's slogan "Every Child Matters" while it was simultaneously bombing children in Iraq.

It's performed by three actors seated in a row on three chairs. Beneath them is a stretch of sand, scattered with lit tealight candles that suggest a memorial to the dead. They glance anxiously at each other before blurting out the standard exhortations. "Your kitchen," they intone, "is a warzone." Your garden is a minefield. Death awaits your children around every corner. Beware! Beautifully judged performances, taking their cue from the tone of earnest social welfare and magazine television, highlight the comic unreality of the rhetoric in the face of those who live in actual warzones. It's simple and powerful and very effective.

For all my reservations, This Is Good Advice is a chance to see a couple of plays by two of Britain's major playwrights that otherwise wouldn't get an airing here, performed by an interesting young company. Well worth a look.