In the world according to Snoo Wilson, Shakespeare is a woman, Christ rides a bicycle and Nietzsche time-travels in a wheelbarrow. His latest play - about the bust-up between Freud and Jung - sounds almost sane by comparison, says Robert Hanks. But only almost.

Some incidents from the plays of Snoo Wilson:

Gorillas emerge from a huge eyeball in the corner of the theatre.

A Cadillac smashes in through a window on the 32nd floor of a skyscraper; a fridge turns into a spaceship, but fails to take off.

Queen Elizabeth I turns the Pope into a maggot, which swiftly matures into a bluebottle and nearly drowns tumbling into William Shakespeare's celestial inkpot (Shakespeare has, of course, chosen to become a woman).

Charles Darwin, on the night of his death, is visited by a Belfast-accented Jesus Christ riding a racing bicycle, and Friedrich Nietzsche, who has travelled back through time in a wheelbarrow; Mary Magdalene descends from a helicopter to treat Nietzsche to a bondage session...

Wilson's rambling, hallucinatory, wildly eclectic and brashly witty theatre is not, you'll have gathered, naturalistic in any accepted sense. Even his most commercial, mainstream work to date, HRH, a study of the Duke and Duchess of Windsor in exile which occupied the Playhouse Theatre last year, strayed a long way from biographical orthodoxy, with its heightened, slangy language, and its references to bizarre sex games.

When we meet during a break in rehearsals for his latest play, Sabina, his conversation proves as rambling and eclectic as you might expect. Unfortunately, it doesn't have any of the energy and wit his stage plays might lead you to expect, at least not to begin with. Asked for a swift run-down on the chronology of his life so far, he rambles rather despondently for 40 minutes, going into interminable detail about petty aspects of plays he did 20 years ago and skipping without comment over huge tracts of time. When conversation turns to his current work, though, he perks up, becoming positively jolly. Apparently, he hates dwelling on the past.

Still, we glean this much: he was born in 1948 in Reading (so that his passport says, he points out with some satisfaction, "Writer, Reading"). His real name is Andrew, but he started being called Snoo when he was about four years old; he either doesn't know or won't say why that is, except that "it's the nicest thing my family called me". In any case, it helps avoid confusion with other Andrew Wilsons, one of whom, coincidentally, is directing Sabina at the Bush.

He studied English and American Literature under Malcolm Bradbury at the University of East Anglia, returning after graduation as writer in residence. There followed time with Portable Theatre and, after that company had gone bankrupt, with the BBC as a script editor and with the RSC as playwright in residence.

He has never managed to sustain a relationship with a major company. Two of his plays, The Glad Hand (the one about the mad South African and the oil-tanker) and More Light (about the Renaissance mystic Giordano Bruno), came out of aborted projects with the RSC; Darwin's Flood was originally commissioned by the National but "They couldn't see it" - it ended up as a sublimely dense chamber production at the Bush.

In the despondent phase of the conversation, Wilson talks as if failure has been the dominant mode of his career so far: there was also a musical version of Around the World in 80 Days, snappily entitled 80 Days, for the La Jolla Playhouse in California: "It was meant to be the toast of Broadway, but the toast got burnt." But, by most standards, he is doing quite nicely. In prospect he has another commission from the National, one from Hampstead Theatre, a musical version of Mayakovsky's The Bedbug (with Gary Kemp, of Spandau Ballet fame) and, in development, a TV drama about a character loosely based on Max Clifford (whom he has been shadowing for some months: "A horrific genius" is his verdict). He has also sold numerous copies of his last novel, about the notorious Twenties occultist Aleister Crowley, mostly over the Internet.

The occult is one of his abiding preoccupations ("I'm fascinated by anything like that, which has confusion at its centre"), although, aside from an inexplicable faith in astrology, he takes a robustly rational view of it. He explains away Crowley's supposedly diabolical practices, for instance, in terms of his bisexuality: "People were not being prosecuted for necromancy, though they were being done for cottaging."

As Wilson says, "I'm not in the business of writing state-of-the-nation plays, except indirectly." That's not to say that his plays aren't about the here and now.

Behind Darwin's Flood and Sabina, which deals with the break between Freud and Jung, lies the thought that "It's impossible to imagine a world where these figures didn't exist and their heft wasn't felt somewhere". The new play is founded on the particular irony that the heroine, Sabina Spielrein, a patient of Jung's with whom he had an affair, may have helped to formulate his ideas of racial consciousness, which were one of the foundations of the Nazis' doctrine of Aryan supremacy. A Russian Jew, she disappeared during the German retreat from Rostov in 1941. For once, it all sounds fairly straightforward - except that it's narrated by Philemon, a winged entity from Jung's unconscious. As always in Wilson's theatre, as in life, history is only half the story.

`Sabina' opens 5 Feb, Bush Theatre, London W12 (0181-743 3388)