He was the patriarch of Modernism. But have we become so familiar with Cézanne's ground-breaking vision that we have forgotten how anxiously hard-fought it was in the making? This son of a banker, born in Aix-en-Provence in 1839, was still in his early twenties when he abandoned his law studies and set out on the artistic course that was to change the entire way that we portray our world. “Cézanne is the father of us all,” as Pablo Picasso said.

A new exhibition sets out to rinse a dried crust of art history from the surface of some our nation's most significant paintings. This week, as the finale of its 75th birthday celebrations, the Courtauld Institute pulls its entire Cézanne stock out of the cupboard and displays them together for the first time.

The Courtauld possesses the most spectacular Cézannes in this country for, at a time when the art establishment dismissed this painter, when the National Gallery carelessly passed up on its chance to purchase a canvas and the Tate coolly rejected the offer of a loan, Samuel Courtauld was buying up canvases at the rate of about one a year.

Times Archive, 1911: Cezanne And Gauguin

Just as Wordsworth was always best inspired when he put some incident of experience into verse without poetic ornament, so Cezanne was inspired by some actual scene or object which he presented with no picturesqueness

• Times Archive, 1934: To meet Cezanne

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• Cezanne in Provence

In the eyes of this philanthropic textile manufacturer, this artist was possessed of a stunning visual magic. Courtauld always remembered the moment he first saw one of Cézanne's works. It was 1922 and a friend, a former airman had led him towards it. “Though genuinely moved, he was not very lucid,” Courtauld recalled. But he managed eventually to get his point across: “It makes you go this way, and that way, and then off at the deep end altogether!”

Now, the Courtauld curators try to take us back to that revelatory moment. They want us to feel Cézanne's magic afresh. So here are some of Modernism's most famous masterworks: the felt-hatted card players, for instance, the pipe-puffing peasant and the Provençal mountain. Even if you've never been to the Courtauld, you will probably know them from books. But it is precisely this familiarity which the show strips away as it tries to remind us how surprising, how peculiar, how intriguingly incomprehensible, each of these pictures might once have seemed.

Of course, this show can't compete with the awesome Cézanne spectacular of a decade or so ago. The institute can stump up only about 20 works. But these, spanning his most important decades, can do a lot of hard work. They are helped out by letters that Cézanne wrote to the young Emile Bonnard, which capture, in a purple and improbably curlicued hand, what probably constitutes the most coherent account of his theories on art. Retranslated, they form a central reference point.

This show sets out to recreate Modernism's “big bang”, by taking us back to the moment of making, to the unsettled surface where mind and matter react. It encourages us to consider how the works are built up from the bottom, and then, once you have reached the top surface, to look at how you might read it right back down to the bottom again.

The show begins with an 1875 landscape constructed with crude swipes of the palette knife. This is a blatant rejection of contemporary academic convention as well as an open display of passion by a man who, in defiance of Manet's fashionable disengagement, believed that “a work of art that does not begin in emotion is not art”. In ensuing oils, we see the invention of his “constructive stroke”, the development of his wilfully anti-illusionistic system of painting. His distinctive patches of parallel marks are emphatically not reproductions of what he can see before him. And yet you can watch him striving, as he explained it, to give concrete expression to his sensory experiences, to somehow capture the sensation of life.

Slowly you fall into the pattern of his pictures. And soon it all becomes very complicated again. You are the observing eye that struggles alongside Cézanne with the complexities of visual perception. As you read his letters, of almost incomprehensible complexity, you can almost hear him screwing his brains up, searching for a language to explain his thought processes. You might be inside the domed cranium (here represented in a self portrait etching), which looked, as Rainer Maria Rilke said, as if it had been formed “by hammering from within”.

With Cézanne's paintings, you might feel for a moment that you are looking at a straight representation of the world. But he pulls you up. This is a picture made up of superficial marks, he insists: and there to prove it is a crude swipe of pigment, a patch of blank canvas, a line that goes nowhere. Until Cézanne, all artists were trying in some sense to re-create nature. He is not even aiming to imitate it; instead he is constructing a “real” artistic world, creating what he called “a harmony parallel to nature”.

His genius was creating a revolutionary way of thinking about perception. He is not a mere Impressionist, flickering back and forth between imitation of reality and superficial patterns of paint. But this “harmony” he sets out to create is not something that can be captured with words. It is something that can be described only in the language of paint.

Reproductions will never express this. Here there are no barrier ropes. The relationship between spectator and painting is direct. It has to be with an artist this subtle. Look at that apple. Every brushstroke seems a part of its substance. The eye grasps it like an object. And yet just as it does so, the apple disappears.

This process of constant renewal is Cézanne's reality. It is this which keeps his work always fresh.

The Courtauld Cézannes, at the Courtauld Gallery (020-7848 2526), Thurs to Oct 5

Living colour: scandalous lives, stunning images - the Post-Impressionists

Vincent Van Gogh

(Self-portrait, 1888)

Van Gogh executed this self-portrait in 1888. The same year, he cut off his own left earlobe and offered it to a prostitute after a violent row with Paul Gauguin. He painted a dozen self-portraits between 1886 and 1889.

Georges Seurat

(Baigneurs à Asnières, 1884)

One of the seven masterpieces from the founder of Neo-Impressionism, prematurely deceased from infectious angina in 1891. This painting is his first major work.

Henri de Toulouse-Lautrec

(At the Moulin Rouge: La Goulue & Her Sister, 1892)

A genetic disease and an intense life in the brothels of Montmartre (where he met Louise Weber aka “La Goulue” - the gluttonous one) didn't prevent him from being one of the most influent Post-Impressionists of his time.

Paul Gaugin

(Tahitian Women on the Beach, 1891)

Gauguin fell in love with Tahiti and the Polynesian Islands and spent the end of his life there. The heavenly islands and their natives fuelled the painter's inspiration and gave him his colourful expressive style.

CHRISTIAN PAMBRUN

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