NICHOLAS WRIGHT'S MASTERCLASS / The Art of Theatre: 15 Magic

THE DEVIL: That is the will of God.

For it is written, Paulo,

Your destiny is Enrico's,

The fate of his soul at death

Is the fate of your soul also.

(The Devil goes)

PAULO: A miracle, a miracle,

A divine holy mystery.

I'll travel to Naples now

And wait for my Enrico,

My spiritual twin brother.

DAMNED FOR DESPAIR by Tirso de Molina, trs Laurence Boswell with Jonathan Thacker

JOSIE: Wait till I tell you something. (Pause) I thought it was a patient because if you saw them you'd know what I mean, there's some of them I'm nothing compared. You'd think I was worse because I've done something but some of them think I'm someone else and I do know . . . What was I saying?

LILY: You thought someone was a patient.

JOSIE: Yes but she's hundreds of years old. And then I was impressed by the magic but now I think there's something wrong with her.

LILY: When you say hundreds of years old, you mean like eighty?

JOSIE: She looks about fifty but she's I don't know maybe five hundred, a million, I don't know . . .

LILY: When you say magic?

JOSIE: I thought maybe she could go home with you.

THE SKRIKER by Caryl Churchill

TONY KUSHNER's Millennium Approaches has a scene between two characters who have never met. Prior, who has Aids, dreams of a woman named Harper; she, simultaneously, sees him in a Valium hallucination. Got it? Now work this one out: in the course of the scene, he gives her a vital piece of plot-information: 'Your husband's a homo.'

Telepathy? Astral planes? All these and more. The point about this Escher-like scene which could never take place is that in psychological terms it makes perfect sense. 'Oh, ridiculous,' Harper explodes. Moments later, doubt sets in: 'Do homos take, like, long walks?' The intuition was there: it only needed the trigger.

Just as in life, magic in plays springs from an underworld: a realm of unconscious fears, unwelcome desires, irrationality, madness. Not as in life, it reveals hidden truths. Its fascination on stage lies in its ambiguity: magic and meaning, both equally 'real', taking turns to edge to the fore. So the fairy world of A Midsummer Night's Dream (to take the obvious example) is both a reflection of human turmoil and its unapologetic self. And Damned for Despair - a gripping religious yarn - is also a study of psychotic projection along the lines of Jekyll-and-Hyde or James Hogg's Confessions of a Justified Sinner.

Paulo, a pious hermit, discovers his secret self in a ruthless bandit. Persuaded that their destinies are shared - that if the bandit goes to Hell (as he presumably will) then so will he - he turns to crime with all the gusto of a man who's been saving it up for years. What has he got to lose? He's last seen sizzling in eternal flames while - surprise - his alter ego, having repented moments before his execution, ascends to Heaven. The moral? God can't be second-guessed. Or, if you like: insist though you might on seeing other people as versions of yourself, they have their own identity - and, tragically, so do you.

Caryl Churchill's The Skriker can be seen - and mostly has been - as the tale of a shape-shifting fairy pursuing and possessing first one young working-class girl, and then her friend, in a variety of human forms: a child, a tramp, a sleazy male groper. It's also that very unusual thing: a play in which madness is seen from within. Rooms, from this point of view, can never be empty: there are always ghosts, invisible forces, memories. Strangers are oddly familiar; if they get on your nerves then they're definitely planning something.

Lily and Josie are like those young women in folk-tales of whom we're told nothing but a basic proposition: 'A girl was on her way to market . . .' or 'There was once a girl so greedy that . . .' All we know about Josie is that she's killed her baby. We find her first in a mental hospital where Lily, her friend, is visiting her. Another patient, Josie confesses, is invading her mind: she's actually not a patient at all, but a supernatural being . . .

It's a familiar scene to anyone who's had a friend go mad. You feel you're about to go mad yourself: it's as though they're offloading something on to you, too painful to bear. Which, looked at one way, is exactly what happens in Caryl Churchill's play. Lily, the next time we see her, finds gold coins springing out of her mouth: her reward for helping a passing Skriker-derelict.

And from now on the Skriker can't let Lily alone. In a bar, a tipsy but well-dressed woman seems strangely unfamiliar with the television, given that she's American. Who is she really? 'I am an ancient fairy,' she confides. Some cases are more doubtful: even Josie, who now sees Skrikers everywhere, is alarmed when Lily attacks a disagreeable little girl in the park. What if it's just a child? But it's the Skriker, of course, disguised as yet another damaged, exhausting stranger.

Or else it's not - and, no less strangely, Josie has given her friend her madness.

Next week: REWRITES