Behind the faded red brick arches of a disused 18th century deer shelter in Yorkshire there is a dark tunnel that burrows deep inside the hill. At the end of the tunnel, there is light. It floods through a perfect square opening that has been cut in the high ceiling of an underground chamber. The square frames the sky. Clouds drift past, their layers of vapour disperse and thicken as blue sky turns to grey and rain clouds gather. There is a flash of black as a bird swoops overhead. Visitors sit silently on concrete viewing benches and gaze heavenwards.

This new work at the Yorkshire Sculpture Park near Wakefield is one of many famous 'skyspaces' designed by American artist James Turrell and installed all over the world - from Jerusalem to Arizona and the north of Scotland.

Sitting inside the chamber, the opening in the ceiling makes the sky seem strange. It is no longer the sky as we normally see it, as something far away and above us. It feels as though it is possible to reach up and touch the clouds. This is what Turrell wants, to bring us into closer contact with light - to draw our gaze up and bring the sky down. To him, a pilot since the age of 16, we are all 'bottom dwellers', an earthy mass, our eyes and mind cast down to terra firma.

'Up there in the cockpit,' Turrell says, 'I've seen so many things that reminded me of this other way of seeing, where light is the material and makes the space. You have to learn this seeing from above. I feel no up or down, it's this new space.'

Turrell studied perceptual psychology at university and he uses light to investigate what seeing actually is- how we form our reality and how deceptive that reality can be. Not only does a hole in the ceiling transform the way we look at the sky, possibly forever, but in other work also on show at the Yorkshire Sculpture Park he demonstrates a similar desire to explore the boundaries of perception; you are led inside a space that is pitch black. Left alone in the dark, there is nowhere to turn, you are enveloped in blackness, lost and disorientated. As your eyes adjust to the dark, the pupil dilates, and very slowly two large oval patches of purple light appear amid the gloom. As you stand and wait, the purple deepens and the black fades to grey. It is now possible to see quite clearly the shape of the room. The light hasn't changed; it is we who are in never ending flux with the world around us.

By showing us the deceptions of sensory information Turrell makes us see that, like in the film The Matrix or in Plato's cave, ordinary appearance does not depict true reality. 'We are caved in. We enclose ourselves in culture and forget where we come from. We have our back to reality and live with the imperfections of perception. I am interested in seeing ourselves seeing. We don't see the way light is used, it is not known to us, most of the time it's an unconscious seeing.'

'People make references to the spiritual. There was light on the road to Damascus and light is associated with this kind of consciousness, this moment of clarity,' he says. There is a spiritual dimension to his work. Turrell comes from a long line of Quakers and although he lapsed for 25 years he is practicing again. The skyspace has the austere simplicity of a Quaker meetinghouse: the walls are painted white and the concrete benches are unadorned.

Quaker's worship in silence; even marriage ceremonies are conducted largely without sound. This space of silence forces you to look and wait. It is in these moments that you discover yourself: your own experience of light, or God, or love, unmediated by an interlocutor hijacking your thoughts and feelings, telling you how to be.

His exceptional way of being in the world, of harnessing the qualities of light and space is at its most spectacular back at his ranch in the Arizona desert where almost 30 years ago he bought an extinct volcano, the Roden crater, into which he has carved a series of 'skyspace' chambers and tunnels; an elegant intervention into nature that is balanced with the moon and stars to create a celestial observatory in which visitors will be able to 'feel the presence of gathered starlight'.

It is a project with neolithic ambition on the scale of Stonehenge - in tune with the landscape, the cosmos and inseparable from its place in the desert. Like Stonehenge, it will be here long after we have departed. Although Turrell talks of how Rembrant and Constable painted the sky and Turner painted light, his work mediates our experience in ways more similar to those of the ancients. In his own words, 'I don't want it to be about light. I want light itself.'

James Turrell's Deer Shelter at Yorkshire Sculpture Park, West Bretton, Wakefield (01924 832631; www.ysp.co.uk) Admission free.