ART / Sacred sights: James Turrell plays tricks on the eyes to disorientate and manipulate viewers. James Hall reviews his work at the Hayward

IN AN imaginary interview with the Californian Light Artist James Turrell, I ask: 'With which figure do you most identify - Prometheus? Columbus? St Francis of Assisi? Goethe? Galileo? Orson Welles? Buck Rogers? The Marquis de Sade?' And Turrell responds, without batting an eyelid: 'No, none of these. The figure with whom I most identify is the manager of Plato's Cave.'

Plato's Cave, if you didn't know it already, is a small guest-house in 4th-century Athens with a bizarre brand of room service. Here is the story so far. The guests have been tied up since birth in a subterranean dormitory. They can only stare straight ahead. A fire burns behind their backs, throwing shadows of various objects on to the opposite wall. These they mistake for real, solid things. Eventually, a guest is released. He turns round, is blinded by the light, but once acclimatised, is amazed to see the objects which are sources of the shadows. He is then forcibly dragged out of Plato's Cave into the sunlight, and is again blinded. Once his eyes adjust, he sees still more objects even more clearly than before. He returns to Plato's Cave, but because he initially fails to see the shadows on the cave wall, the other guests claim that his trip to the outside world ruined his eyesight, and was thus a total waste of time . . .

James Turrell has been providing equally unsettling kinds of room service for over a quarter of a century. Some of it can now be experienced in three separate room installations on the top floor of the Hayward Gallery. In order to reach two of the rooms you have to shuffle along a narrow, pitch- black corridor, making sure that you stick to the left-hand side. At the end of each corridor you turn a corner and enter a dimly-lit space. Once inside, weird and wonderful light-shows, almost impossible to describe, unfold before your very eyes: here darkness is made visible, light made material.

Turrell was born in Pasadena in 1943. Before deciding to become an artist, he took a degree in perceptual psychology. He says he chose to work with light after being impressed by the luminosity of Abstract Expressionist artworks seen in slides, but disappointed by the drabness of the originals. His first installations were made in the late Sixties in two refurbished rooms of the former Mendota Hotel in Ocean Park, Santa Monica. Since 1979, however, he has turned his attention to Roden Crater, an extinct volcano in the Arizona Desert. It is a colossal project, financed by grants and sales of work. The rim of the crater has been reshaped, and an internal network of passages and chambers is being built. On completion in the year 2000, the crater will have been transformed into a temple to light and darkness.

The groundwork for the Roden Crater project, and for the three rooms at the Hayward, was laid during Turrell's time at the Mendota Hotel. On arrival, he sealed off the rooms from outside light, built false walls, covered the surfaces in smooth plaster, and painted everything - floors included - white. He then projected square and rectangular beams of high- intensity light across the corners of the rooms and on to single walls. Depending on the distance of the viewer, the projections looked like flat planes or three-dimensional blocks of colour. The effect of periodically perceiving light 'as a tangible material' was disconcerting, to say the least. Turrell says he is 'interested in a place where the imaginative seeing and the seeing of the external world meet, where it is difficult to distinguish the seeing from within from the seeing from without'. He is a manufacturer of waking dreams.

Wedgework IV, one of the installations at the Hayward, was completed in 1974. You stand behind a rope at one end of an enclosed rectangular room, looking towards an oblique wedge of reddish light that fills the far end. The left-hand wall stops short of the right-hand wall, and fluorescent light is projected from behind it. Somehow, as the light goes from left to right, it changes from opaque to transparent, from thick to thin, getting whiter as it goes. Turrell, who is also a trained pilot, says that, when flying, a similar 'differentiation of vision happens through weather and water vapour'. For the viewer at the Hayward, this multi-textured mirage gives a sense of vertigo. It is almost as if you had a ring-side seat at the origin of substances.

There is no denying the method in this visual madness. Having already studied perceptual psychology at university, Turrell took part in an Art and Technology programme at the Los Angeles County Museum. Here he collaborated with Dr Edward Wortz, a physiological psychologist who was researching extra-terrestrial conditions for NASA's Apollo Program. Together they studied sensory deprivation using an anechoic chamber. This controls sound and light. Some subjects were brought to the chamber blindfolded to see how this altered their perception of the space. They also produced Ganzfelds, total visual fields in which there are no objects to take hold of with your eye; it resembles a dense fog of colour that extends indefinitely into the distance.

Trace Elements (1990), another of the works at the Hayward, allows you to put your hand and head into a Ganzfeld. This time a rectangular room is lit from three sources: from two spot-lights directed on to each flanking wall, and from a glowing rectangle that extends across a facing wall. Initially the rectangle looks like a cinema screen, lit but imageless. The colour is mauve with white tinges. As you get closer, you notice that no shadow is cast on to the screen, and that there are no reflections. It dissolves into a wall of fog.

You have an irresistible urge to try it with your hand, and instinctively but irrationally expect to feel something solid. Yet you grope into nothing - into thick and thin air. The realisation that what seems solid is actually empty makes you feel very alone, and rather cheated.

Turrell's work has always had ritualistic elements. There is the queueing to get in, the dark corridors, the waiting for your eyes; then there was the pilgrimage to the Mendota Hotel, and now to the Arizona Desert. But over the years the ritualistic aspects have become increasingly extravagant and overt. The chambers inside Roden Crater (represented here by models, photographs and plans) are organised to interact with natural light in ways which are modelled on ancient sacred sites. Moreover, since 1988 Turrell has been devising white temple-like structures similar to 18th- century visionary architecture. They come with a wide range of idiosyncratic and often menacing titles. These evoke science-fiction (Afrum- Proto, Alien Exam), science-fact (Mapping Spaces), romanticism (Deep Sky), paganism (Human Sacrifice, Fire Eater, White Blood), tribalism (Boullee Boula), or the wild west (Bullet Head).

Some of them echo the symbolism of the Masonic initiation ceremony - the so-called Trial by the Four Elements. In the Trial by Air the initiate is symbolically hoisted up into a domed space into the presence of Wisdom; something similar occurs in White Blood: the viewer lies down on an altar-like platform before being raised up into a domed Ganzfeld space overhead. The Trial by Water, which involves swimming across a difficult stretch of water, was much in evidence in an extraordinary installation in Poitiers in 1991. Here the visitor had to strip, shower, put on a Twenties-style tank-top swimming costume, and then dive into a square pool and swim under a wall. You emerged inside a white light-filled cube open only to the sky. This cube was similar in effect to Air Mass (1993), a stunning tent-cum-pantheon that has been erected on a roof terrace at the Hayward.

Sadly, not all initiates pass Turrell's tests. After an exhibition at the Whitney Museum, New York, lawsuits were brought against him by viewers who sprained wrists or broke arms after falling into a Ganzfeld piece, City of Arhirit. A double injury was sustained by at least one visitor to Poitiers. The first injury was a dislocated arm, caused by swimming into the edge of the semi-submerged cube. The second injury (and much the most serious) was the humiliation of being rushed to hospital wearing a tank-top swimming costume. There is less to fear at the Hayward. You do not need to shower. You do not need to strip. You will not be hoisted. You are unlikely to fall. The trickiest bit is entering and leaving along darkened corridors: you may bump into a body coming the other way . . .

Turrell is one of the most compelling installation artists at work today. Accounts of his work as 'quiet and meditative', which perpetuate the myth of Turrell as a dozey hippy, misrepresent him. Turrell's oeuvre is as much a theatre of cruelty as it is a theatre of contemplation. It also inspires trepidation, deprivation, humiliation, embarrassment, gullibility, absurdity and fear. Visual art usually invades the head; Turrell hopes to invade the entire body. He has a dream of a completely captive audience. We are familiar with the idea of there being a Thought Police; Turrell's manipulations hold out the possibility that there could even be a Sight Police.

(Photograph omitted)