The director Mick Gordon says that he has gone through a period of "soul-searching" and wryly concedes that this sounds a mite ironic in the current circumstances. For On Ego, his first show in England since 2002, explores the implications of the scientific claim that our sense of having even a self - let alone a soul - is a fiction relayed to us by that inveterate story-telling machine, the brain. Gordon developed and wrote the piece in collaboration with a neuropsychologist, Paul Broks, whose poetic and powerfully suggestive book Into the Silent Land is a miscellany of real-life case studies, intimate personal confidences, sci-fi scenarios, and philosophical reflections that muse - in the tradition of Oliver Sacks - on what neurological damage can tell us about the brain-processes which construct the experience of personal identity, and on the vexed issue of whether the mystery of consciousness (how "meat becomes mind") can ever be solved.
When I first met Gordon seven years ago, it was clear that here was a young man who was going to go very far, very fast. Even the premature baldness of this Northern Irish charmer seemed to be part and parcel of a general aura of focused precocity and swift intent. He presided over a golden era as artistic director of London's Gate Theatre. A close protégé of Peter Brook, he was snapped up by another luminary, Peter Hall, to work alongside him on the vast Tantalus cycle in Denver (a project from which Gordon beat an early retreat, professionally unscathed). Trevor Nunn then welcomed him aboard to lead the National's Transformation season, producing a more youth-conscious programme for the reconfigured Lyttelton and the new (though temporary) Loft space. That accomplished, Gordon seemed suddenly to fall off the radar. Where has he been, and why?
"I'd got to the point," he tells me, after a morning's rehearsal, "where the next logical move was to run a theatre again, but I thought that if I did that I would just be doing what was expected of me. I needed to ask myself what kind of work I wanted to make and what authorial responsibility would be mine. So I basically took a leaf out of Peter Brook's book, and travelled." He has been on long, investigative assignments in Uzbekistan, Lithuania, and Uganda, interspersed with wallet-replenishing stints in Stockholm, where he has directed Pinter, Stoppard and a new, piquantly trilingual and tragicomic piece by Nick Grosso, A Play in English, Swedish and Italian, about the media and Sven-Goran Eriksson's various amatory entanglements.
"I chose places where theatre directors have a very clear sense of what they are doing their work for. In Uzbekistan, for example, there are no civil or human rights and the Ilkhom Theatre in Tashkent is a place of freedom through metaphor and poetry and imagination. They have a brilliant complicity with their audience." At the Gate, Gordon had experimented with devised pieces, such as Intimate Death, a beautifully judged meditation on dying as a process of discovery, inspired by the writings of Marie de Hennezel, the chief psychologist at a Parisian palliative care unit for the terminally ill.
After the Transformation season, Gordon was invited to re-develop another of these Gate shows, Love's Work, in Tashkent. Uzbekistan didn't know what had hit it, as teams of interviewers, armed with Dictaphones, combed its regions, approaching total strangers for their personal stories. Five hundred of these were collected and staged in On Love, a collage of testimonies that offered multiple perspectives on the subject and was an inherently subversive gesture in so repressed a country. The piece is regularly updated. "It's my longest-running show to date," smiles the director.
This exercise resulted in the desire to found his new company On Theatre as "a vehicle that would use the tools of the medium and its human scale to create Montaigne-type essays - in both senses of the word: reflections and attempts". Gordon certainly can't be accused of jumping in at the shallow end with On Ego and its ponderings on the conundrum of consciousness and personal identity.
In Into the Silent Land, his collaborator Paul Broks invites us to contemplate mind-bending and heart-rending cases such as the woman suffering from Cotard's syndrome, a nihilistic delusional state which may be due to a decoupling of feeling and thought. It suggests that merely thinking that one exists may not be sufficient. The idea must also be felt. Descartes's dictum must therefore be amended to "I feel I think, therefore I am". At one point, Broks refers to certain categories of brain-damage as "thought experiments made flesh". And that, of course, would be a good definition of some kinds of devised theatre.
After over a year of reflection and periodic workshops, On Ego emerged as a scripted play which has just opened at the Soho Theatre, in London. "The debate in the piece", says Gordon, "is between bundle theory and ego theory. We know, neurologically speaking, that the mental processes underlying our sense of self are scattered through different zones of the brain. There's no point of convergence, or inner sanctum of self. Our brains literally make us up. Bundle theory endorses the neurological truth. Ego theory is simply the common, intuitive illusion that behind every face, there is an essence, an ego, an 'I', a central core. Our protagonist, a young neurologist, starts off as a committed bundle theorist."
Then, though, there are two dreadful developments. One is based on a "what if?" scenario, indebted to both Star Trek and the great Oxford philosopher Derek Parfit. The piece takes place in a world where the teleportation of people is possible through the transmission of digitally encoded information about them. The original person is always vaporised in the process to prevent doubling. But a hitch occurs, and the protagonist, now arrested and threatened with execution, must face up to the fact that a replica, who has perfect psychological continuity with him, has gone to meet his wife for dinner. According to his own theory, it shouldn't matter to him that the life he would have lived and the books he would have written will now be achieved by this indistinguishable surrogate. But it does, and the horror of his predicament is compounded by the fact that the wife is succumbing to Capgras syndrome, the neurological delusion that someone you love has been replaced by an impostor.
The resulting drama is both philosophically stretching and gut-wrenchingly ambivalent, making creative capital of the fact that actors, by virtue of their work, are natural bundle theorists and that theatre is adept at finding physically immediate metaphors for difficult concepts. "I think that Broks would say that the soul is an illusion," Gordon explains, "but that this certainly doesn't mean that it isn't important. The difficulty comes when we don't recognise that it's an illusion because brains have bodies to fight for what they think is real. The history of religion shows how constructive that can be," he adds dryly.
It's no coincidence, then, that the company's next project is On Religion, a collaboration with the philosopher A C Grayling. "This is the most rewarding work I do because I'm educating myself," the director announces. "But it's an expensive and lengthy process. Even to begin a serious conversation, the amount of reading and time spent in the company of experts is huge."
Let's hope that continued Arts Council support and Gordon's canny financial juggling of side-projects will mean that On Theatre can fulfil its promise of being an education to its artists and audiences alike.
'On Ego', Soho Theatre, London W1 (0870 429 6883) to 7 January