The secrets of timeless drama

The Young Vic theatre has prepared a season of playwrights' debuts. David Lan, its artistic director, reveals some trade secrets

You're on the Heathrow Express. Let's say there are a number of realities: the train; you and your fellow passengers; the suburb of west London through which you're travelling; your immediate destination (Heathrow); your further destination (Bradford, Baltimore, Beijing...). Then there are your thoughts triggered by the book you're reading, and then the special edition news on the monitor begins. This is a total of seven realities, all independent of each other. The news concludes. The train arrives at the terminal. You head off down the platform. The other passengers go their ways.

Or, again, you're on the Heathrow Express. You're reading your book (a tourist guide to Barbados); a passenger is struggling to get a suitcase out from under his seat, trying too hard which is why it jams - no one else pays him attention; the news on the monitor drones on - more bombings in Baghdad; a woman passes through the carriage pulling a reluctant child through the connecting door, which slams; the struggling man abandons his case and darts out after the woman; suddenly the TV flickers and dies; then the train picks up speed - the passengers look up, alarmed; through the window, in the skies over Hammersmith, smoke is gathering; your tourist guide conceals a square of paper on which are scrawled 10 words in a foreign language, phonetically transcribed... your lips move as you practice saying them...

It's only when every level of reality is connected to, and resonates with, every other that a play acquires real energy and power. Think of Troilus and Cressida, think of The Cherry Orchard, think of Arcadia. Where are we? Where do we think we're going? Who are we going there with, or in spite of? Where do we plan to move on to when we've got there? What is the nature of the world within which we live? Who are we?

Genius in theatre is about how many separate realities can you squeeze onto a stage, and how complex can you make the dialectic between them?

Or, to put it another way: in Hamlet, everyone who is anyone has a scene with Hamlet - even Fortinbras, though by this time Hamlet is dead. If they didn't meet Hamlet we'd have no interest in them. And with each meeting we learn something contradictory about him. Imagine the skill it took to pull that off. How many playwrights have achieved that since then?

Second criterion: The power of the present

The coincidence of Look Back in Anger and Waiting for Godot both being around 50 years old has sparked the question: which is the truly radical, and which is the more profoundly innovatory? Of the two writers, who is the real genius of 20th-century theatre? In fact, in these plays at least, both Beckett and Osborne shared the crucial ingredient, the catalyst without which theatre is inert: immediacy - the only reality is the one that is actually unfolding in real time before your eyes.

Since the Victorians, and through the 1930s and 1940s, most English plays blanketed themselves in exposition, or "back story" as film people call it. This a polite way of talking about the expression of ideology by the technically unskilled. The writer knows precisely where they're leading us and is determined that we share their understanding of what that place means. Even the most accomplished of playwrights - Lonsdale, Coward, Maugham - make as little allowance as they can for ambiguity. This necessitates that their characters spend much time inert - often lazing on settees, chewing over with each other their own past histories and preparing for the moment when disaster occurs, usually a few minutes into act two.

Beckett never had use for settees. In Godot, there is no reality but the one before your eyes. No information is given which is not contradicted. (The same is true in Shakespeare and Chekhov.) In Anger, Osborne still needed the settee. (It had gone by Luther and only returned when his ideas ran out of steam.) He came within an ace of achieving Beckett's control of the passing instant.

In the 1920s, the German Expressionists and Brecht had been after the same thing. Though they carried a heavy freight of ideology, they believed that theatre should be like music: its power decaying from the instant it was born. Theatre as fruit fly, or as bullet.

In the truly sensuous there is nothing redundant. To achieve that - as Robert Lepage does even, as in The Dragons' Trilogy, in a show lasting five and a half hours - takes genius.

Third criterion: Pain

The theatre of Europe is like a biscuit: twice baked, twice born - both times in the fire. The first baking was in the Greek Dionysian ceremonies of the death of winter. The second baking was in the ritual of the late medieval church: the acting out of the passion of Christ. You might say that the Renaissance was an astonishingly swift accretion of skill and technique so that audiences would feel, ever more acutely in their own bodies, the actual experience of the crucifixion; so that they would share Christ's suffering.

The key to dramaturgy is conflict. From Oedipus to Ayckbourn, at the centre of a play is a suffering human being. We may be appalled by the horror (Titus Andronicus) or cry tears of laughter (A Flea in her Ear). As Kenneth Tynan put it, "Whether in a farce like Charley's Aunt or a tragedy like King Lear, the behaviour of a human being at the end of his tether is the common denominator of all drama."

Our fourth criterion: Just do it

Plays for our Young Genius festival had to have been finished before the writer was out of their twenties, so they must have grasped the previous three criteria the moment their writing lives began. That this can happen seemed to us a sort of miracle which we could not explain - is genius hard-wired? - but which seemed good to celebrate. Soyinka, Kane, Marlowe, Schiller, Brecht, Jarry, Beaumont, Büchner. Geniuses all? Are my three criteria fulfilled? Or redundant? Take your pick of what's on show at the Barbican from now until November and let us know via the website.

The Young Genius season, Barbican Theatre, London EC2 (0845 120 7511; www.youngvic.org), 16 September to 10 December