More and more often in theatre, a space once sacred is being invaded. Between the stage and the seating arrangements there is no longer always a gawping, uncrossable chasm. Pan Pan is one theatre company that taps the potential of artist/audience interaction in particularly memorable ways; the most frequently asked question after performances of their piece Standoffish is: "Did you get a hug?"

So, with Pan Pan at the helm, it's no surprise that the fourth Dublin International Theatre Symposium offers a programme of events devoted to the bridging of conventional distances. There are demonstrations of work in progress and open discussions with practitioners that bring the audience closer to the inner life of the performance, to the mechanisms of creativity.

But it's the impressive range and scope of the theatre workshops on the programme which attests to the company's determination to tear down walls. Because only amid the rubble of such walls can the theatre workshop take place. The workshop breaks art down to its first components and, through collaboration, builds it up again.

Each workshop running during the week of the symposium does this in different ways. In some, participants work with text, in others with movement or sound; sometimes they work merely with thin air. From the outside, these approaches seem impossibly different; but on the inside, everyone works towards the same goal.

The first two days see two different workshops given by two different companies. The gap between them couldn't seem wider. While Corcadorca, over the course of the week, are putting through its paces the script of the powerful drama which won second place in their Playwright Awards 2000, and staging it on Friday night, the madcap English company Ridiculusmus have a far less concrete plan, simply entitled "A Day Devising".

First impressions certainly suggest that these companies are polar opposites when it comes to putting together a work for theatre. Corcadorca have chosen the small, dark space of the theatre in the City Arts Centre for their workshop. With the playwright Jerry Twomey, who has taken a week's leave from his job as a stage constructor in Cork, and the script of Noose, seven of us huddle around a table and listen to the play read aloud by the two actors who will perform it. Brid McCarthy reads the lines of Twomey's unspeaking woman, and Niall Cleary, who will play her younger unspeaking lover, reads the stage directions. Nobody moves yet.

It's a different story over in the dance studio of the Samuel Beckett Centre with its enormous window of daylight and its wall of mirrored glass. Everywhere lithe bodies in loose clothing are stretching and stepping and limbering up. From a distance, the workshop leaders Jon Hough and David Woods observe the preparations. As the hour approaches, the noise level rises. Anticipation is growing, and nobody knows quite what we will be doing. When the Ridiculusmus crew gathers its ensemble of dance students, actors and artistic directors, it is announced that this is a day of free-form improvisation, the technique the company uses to devise its own material.

Working only with the resources of our own imaginations and the vast space of the floor, we will be sent out in groups of three to fill 20 long minutes of silence. The comfort of a script in hand, and the panic of blanking in front of a waiting audience - could the situations be more different?

Of course, such diversity in approach and attitude is what justifies the existence of a theatre symposium in the first place. No one would celebrate a culture of cloned ideas. And yet, once both groups begin to get their hands dirty with the real business of building a play, they begin to dig towards a common ground. On that ground meet the impulse toward free play which fuels Ridiculusmus, and the need for shape and structure so appreciated by Corcadorca.

In the City Arts Centre, as the actors read through the Corcadorca script, something is beginning to happen. McCarthy's clear reading voice is being taken over by the voice of someone else. The suffering of Twomey's woman is beginning to weigh every word. Across the table, Cleary's face begins to register anguish, disgust, terror. His features contort with the horror of his character's predicament. Gradually, imperceptibly, but undoubtedly, a metamorphosis is taking place, unscripted, unplanned, almost improvisational.

The playwright is deep in concentration. This is the first time he has heard his play read aloud. He catches every word, and he knows where every word should be. He is the one who will notice every slip of the tongue, wince at every accidental stumble. And yet, he has agreed, he is willing to let the words be moved, changed, abandoned if the actors, the director, feel they do not scan.

"Whatever it takes," he says. "I would hope that I wouldn't be too precious in that regard, that if something works I won't argue with it."

Twomey faces his first challenge after the first reading. The feeling is that something crucial is not clear. Nobody has understood the precise nature of this woman's loss - the loss of a baby boy - but he is stunned that we do not understand. To him, her every word points to the event which has scarred her, the event which he does not want to state crudely. He does not want to make her say the word which is, for her, unspeakable. He tries to help us to see, quoting lines which say it all for him, but we have missed them, as an audience does.

"It's lost in itself," the actors tell him. "It's veiled by too many words."

And he is faced with the ordeal of meeting our demands without destroying the work, without turning it into an issue play, which he dreads.

"She can't ever say the word," he says after some thought. "I'm putting my foot down on that now."

What has been recognised is the conflict which drives these workshops, and one which the participants in the Ridiculusmus day can understand only too well: the conflict between the urge to let creative ideas flow unhindered and the need to channel them into a clear structure. David Woods explains that it is possible, and essential for their piece, to strike such a balance.

"The desired state is to get locked into character to such an extent that you are in a sort of trance," he says. "But you have to think about direction and structure too, so even while you're not thinking, you must be thinking." This is the achievement towards which the Ridiculusmus trainees strive all day, but it doesn't happen easily. Without a director for guidance, and growing dizzy with panic in the performance space, shaping and sustaining a credible character seems an impossible task.

But from the debris, inklings of possibility, germs of ideas are salvaged - nothing is wasted in the workshop environment. Ideas flow together, or they clash; something fits perfectly, or it sticks out a mile. A glaring error, a careless judgment, a missing clue, can only be spotted from a place outside that zone of intimacy with the work.

Very quickly, it's easy to see what the experience of the workshop is about. It's about interaction and interrogation, about the freedom to change and the wisdom to cut. And about being wrong, about the importance of making mistakes.

"Now, you're all quite likely to fail," we are informed by Ridiculusmus before embarking on our attempts at improvisation. "But failure is very productive. And we can't really stress the depressing, boring, mind-numbing nature of the process of working to the result, of getting there."

Jerry Twomey would agree. "It's hard work," he says. "In a way, I'd rather be loading and unloading vans tomorrow, setting up stages for orchestras and letting them do the singing and cope with the work, you know, but it has to be done. It has to be done."