TURNING POINT / And then there was light: For a 15-year-old boy interested in English parish churches and baroque country houses, the theories and architecture of Le Corbusier came like a bolt from the blue. By Jonathan Glancey

Le Corbusier was a painter, sculptor, journalist and propagandist who broke every rule in the canon of architecture, including his own. His face was as iconic as his buildings: long and grave, it appeared to be carved from stone. It was framed by those thick round spectacles without which it seemed hypnotically blank. Meeting him in 1950, the English architect Robert Furneauz-Jordan thought he looked like an Easter Island statue.

Le Corbusier was the Picasso of his art. Like Picasso he did not cease from experimentation and so remained popular with the young of all generations.

I was a teenager when I first came upon his work. I was 15, with a head crammed with parish churches and baroque country houses, and a contempt of the Gradgrind, gimcrack and venal grunge surrounding me in London. I did not come from a family of artists or architects and the idea of new architecture as something that could be inspiring was foreign to me. And then, in a library, I discovered Le Corbusier's much misquoted essay Vers une Architecture (1923).

I read it several times, trying to make sense of the curiously related images of cars, ships, planes, medieval cathedrals and Greek temples. Here was that infamously misrepresented phrase 'the house is a machine for living in', which the English have misunderstood ever since to mean that Le Corbusier was a brute functionalist with a mission to box us up in claustrophobic concrete tower blocks. (He meant no such thing: 'Functionalist: this frightful word,' he wrote, 'was born under other skies than those I have always loved - those where the sun reigns supreme.') To me, it was a riddle - a riddle that could only be solved if I saw the architect's work for myself.

Le Corbusier designed and built houses and congress halls, pavilions and churches in Europe, Japan, India, in both North and South America. There is, of course, no building by him in little Britain. So, that summer, I went by train, bus, foot and autostop on pilgrimage to the village of Ronchamp in the Vosges in France, to see the Chapel of Notre Dame du Haut (1950-53). Ronchamp was a revelation of the true Corb, a building that made the most masterly and magnificent play of light on a structure at once ancient and modern.

Services are held inside and outside the building and so the exterior is an unwalled room framed by nature, rather than a barrier separating exterior from interior. Walls, roof and towers refuse to obey laws of conventional geometry. Find a straight line and you win a plenary indulgence. Corb drew the design of the building with a crab-shell by his side as reference and inspiration: Ronchamp draws as much from Nature as Euclid.

The upswept roof is supported not by the unbuttressed rubble walls, but by slim concrete pillars set into them. These lift the roof six inches above the walls so that a band of sunlight plays magically around the nave. The roof might look massive, but its structure is ingeniously lightweight. It is formed of two skins separated by a six foot void.

Inside, the convex roof curves across the nave. While sunlight gleams through the slit between roof and walls, a rainbow of light plays through the small painted windows punched through the 10 ft depths of the walls. The effect is always the same. It quietens people; it stills our turning worlds.

Corb was an atheist, but in this little building he invited the God of light to enter the pilgrim's eye. I have no fixed idea of what God meant to Corbusier, but from Ronchamp and his later Dominican monastery at La Tourette, near Lyon, his God had more to do with Turner's and Teilhard de Chardin's than it did with those who throw honest vicars out of livings or pray for the death penalty for adulterers.

His vision was certainly godly and thus far removed from the vast majority of architects of his or our day. This concern with the infinite explains why his later work is often called 'timeless'. In concrete and rubble, Ronchamp embodies the antique spirit of churches found among goats and olive trees on Aegean islands, of the numinous quality of light dancing in the Hagia Sophia, of the massiveness of old masonry walls.

It is a passionate building, creating drama out of inert materials. It is a creative risk realised solidly by local masons. It represents the point where the architect's essentially religious nature met the body of doctrinal faith.

Le Corbusier lived a life of aesthetic asceticism. He did not own a big house. His monastic office at Rue du Sevres was tiny, his apartments small, his beach hut no more than a timber seashell. He once owned a green Fiat Topolino, but preferred to walk and, when in Paris, he took the Metro.

An outsider in every way, he did not train as an architect. He was a Swiss watch-case engraver who, as Charles- Edouard Jeanneret, went to art school at Chaux-de-Fonds at the age of 13. A few years later, he spent his small savings visiting the ancient architecture of the Mediterranean and finding work in the most imaginative studios of his day: Josef Hoffman's Wiener Werkstatte, the buro of Peter Behrens in Berlin and the atelier of Auguste Perret in Paris.

He was a dreamer and a doer. He had the timing, logic and matter-of-factness of a Swiss Waldensian and the sensuality of a Mediterranean pagan. He found the French metric system of measurement inhuman and so devised his own, the Modulor, based on the rule of elbow, pace, foot and thumb. He was born in the cool of the Swiss mountains and died in warm summer waters off Cap Martin.

At Ronchamp, Le Corbusier brought the strands of his work together. Here, he stepped from the cool, mathematical sonnets of his forties and fifties into the baroque lyricism of his sixties and seventies. At Ronchamp, Apollo extends a hand to Dionysius.

Here, one intuitively understands Le Corbusier's much repeated distinction between looking (cataloguing, collecting, listing, notating) and seeing (understanding, connecting and finally creating). One sees, too, that unlike the honours- seeking architects of our day who play with or try to re-create past styles, a great architect is rightly absorbed with the past, but uses it as an artist not as a historian.

'Architecture,' said Corb, 'is not an ostrich feather stuck with or without grace in a hat by the diligence of a modiste. Architecture is the spirit of truth.' At Ronchamp, it really is.

(Photographs omitted)