Vincent van Gogh: the complete letters, Edited by Leo Jansen, Hans Luitjen and Nienke Bakker

Born into a Protestant clergyman's family, his childhood steeped in Good Book and the liturgy, this turbulent young visionary in search of a sacred vocation dives early into literature and never wants to surface. Charles Dickens becomes a lifelong friend; George Eliot a touchstone of his reverence for working folk. Though the language of the Bible guides his thoughts and shapes his style, he swims happily in the classic poetry of French, English and his native tongue. As for Victorian illustrated magazines, he loves them so much he wants to find a job with one.

A move to Paris plunges him into the milieu of Flaubert, Maupassant and Zola, with all the grandeur, heroism and tragedy that the naturalists found in everyday life. Throughout, he evokes, justifies and analyses his works, his feelings, his ideals in an unstoppable torrent of self-expression. Near the end, a shattering crisis sees him find solace in Dickens's Christmas Books and Shakespeare's history plays. "It's so alive," he writes of these characters during a fitful recovery from his breakdowns, "one thinks one knows them".

If this sounds like a biographical sketch of a writer, then it is. No great visual artist ever wrote so much, and so well, as Vincent van Gogh. We have 819 letters from him and 83 to him (he was careless about keeping correspondence). The 658 to his brother, supporter and comrade-in-arms, the art dealer Theo van Gogh, constitute as rounded and forceful a spiritual autobiography as any in the Western canon.

And all this endless self-interrogation happened as he turned his life upside down in wrenching moves from his North Brabant home to southern Belgium, London, Antwerp, the Hague, Paris, Arles – even Isleworth in 1876, when the young man who still hoped to preach the Gospel gave his first sermon at the Methodist church near Kew Gardens and wrote to Theo of an autumn walk beside the Thames "which reflected the large chestnut trees with their load of yellow leaves and the clear blue sky, and between the treetops the part of Richmond that lies on the hill, the houses with their red roofs and windows without curtains and green gardens... and below, the grey bridge with tall poplars on either side". Vincent, whose flair for painting vibrant verbal landscapes never dimmed, had at that stage scarcely lifted pencil or brush.

"My professor used to say that Van Gogh didn't die aged 37 but 74, because he lived at double speed," comments Nienke Bakker, an art historian at the Van Gogh Museum and one of the editors of this superbly researched and gorgeously produced edition of his letters. Around 120 have gone on show alongside related artworks by Van Gogh and his peers to mark the culmination of 15 years of study by the Museum and the Huygens Institute. As for these six sumptuous and scholarly volumes, with more than 4,000 illustrations and a comprehesive editorial apparatus that never gets in the way of the reader's enjoyment, £325 may look a steep price for a set of books. Given the quality of the production, and the marathon of multi-national research that has led to this definitive edition, it ought to sound a bargain. Selections from the correspondence began to appear in 1893, three years after the artist's death, and several landmark editions have followed. Yet no systematic illustrated and annotated version available in English has existed until now. At last, Van Gogh speaks at full volume.

An even more complete online collection went live this wwek at www.vangoghletters.org. "It's entirely free of charge for everyone in the world," stresses co-editor Leo Jansen, who has worked on the project since 1994. "I'm very proud the Museum has decided to do this. We are a public institution."

In the letters, every twist of Van Gogh's lurching career comes alive with passionate descriptions, disputes and defences that leave no step unscrutinised and no painting unannotated. We can trace the course of his early piety and social activism, his apprenticeship in the European art business with Goupil & Cie, his doomed love for the ex-prostitute Sien Hoornik, the agonising struggle to make his own wayward talent blossom, bohemian adventures, revelations and breakthroughs in Paris, the climactic dream of fulfilment in art and life through the Arles "studio of the south" - and the uneasy peace of its aftermath in the Saint-Rémy asylum.

For Vincent, the unexamined life was not merely not worth living; it was never lived at all. "There's always something at stake," according to Leo Jansen. "He wanted to reach for the essence of things. He wanted Truth with a capital T." And always, from that golden autumn day beside the Thames to the sea-like wheatfields of Auvers-sur-Oise shortly before he shot himself in July 1890 – "delicate yellow, delicate pale green, delicate purple of a ploughed and weeded piece of land"- that truth comes in colours, gloriously conjured.

In direct and dramatic language, the letters paint a self-portrait of the never-satisfied idealist. As Jansen notes, he "always felt himself on a mission... to do great deeds and to make himself useful to society". Arguing, cajoling, inspiring, preaching all the way, Van Gogh first embraces then spurns orthodox religion, takes up a romantic creed of art, seeks to ennoble the poor, to enrich the dulled senses of his fellow-citizens and – finally, fatally – to refashion art itself into a window on a rainbow-hued Utopia in Provençal light.

"Underneath, there's a system of values and principles that's really very consistent," says Jansen. "You've been given life, and you have to spend your life proving that you're worth it". Driven by words and concepts before any radiant images ever danced to their tune, this faith in personal vocation and methodical labour feels not so far from the pieties of his father. Yet it's a million miles away from the Hollywood myth of a deranged ear-slicing genius who chucked paint at canvas in fits of delirium. But then, as Jansen comments as his own long and heavy task at last reaches fruition, "I have rebelled against the myth since the day I started."

Nienke Bakker gave me a sneak preview of the Amsterdam display. As we gingerly lifted up the brown paper that still covered the panels, workmen sawed and hammered to finish off the cases in preparation for this week's opening. The writer-artist would have been in his element amid this honest toil. I can't read his Dutch, but Vincent wrote around a third of all his letters in French. From these, one idea leaps out from these faded pages covered with artfully placed sketches of work-in-progress.

When Vincent writes travail or travailler, as he often does, sometimes the "t" stands proud of its fellow letters – like a solitary reaper, or an artist at his easel. Work will make him, and us, free. "It's only when people have all the rest that they get a feeling for, need for paintings, books etc," he writes to Theo in 1889. "So in my own estimation I definitely reckon myself below the peasants. Anyway, I plough on my canvases as they do in their fields."

And this work feeds on words. Mostly to Theo, but also powerfully to fellow-artists, and touchingly to little sister Willemien, Vincent never lacks for them as he so often lacks for paints, purchasers and cash. As the editors put it, "he may have wrestled to master the arts of drawing and painting, but he was born with the gift of words". "There's the art of lines and colours," he writes to Emile Bernard, "and there's the art of words that will last just the same". With his words and visions united in all their blazing intensity, this momentous edition at last completes the palette of Vincent's double art.

'Van Gogh's Letters: the artist speaks': Van Gogh Museum, Amsterdam until 3 January