We all think we know Surrealism. Its imagery, its juxtapositions and paradoxes, its reach into the subconscious of dreams and imaginings has become so much part of the visual language of commerce as well as of art that it is almost impossible to conceive of the last century without it. And yet its very popularity has made us forget what its artists and poets were actually trying to achieve – to make us see the world and ourselves afresh.

Of no artist is this more true than of René Magritte, the great Belgian Surrealist. His images of the bowler hat, the loaf clouds and the falling rain of figures, have become the best-known symbols of the movement and the instantly recognisable reference points of advertising as well as popular art. And yet the intention of this purist of the Surrealists and the most literate and articulate of its painters, has somehow been lost in the popularity of his works. He, who had hoped to open our eyes to a new way of looking through the simplest of forms, has been obscured by their very success.

It's a paradox which the Tate Liverpool is hoping to address through an exhibition later this month, the first major show of his work in this country for a generation and, so the gallery boasts, the biggest ever held in the UK – a hundred paintings alongside drawing, gouaches, examples of the commercial work he undertook and some of his home movies as well as his later sculpture.

"The object", explains the curator of the show, Darren Pih, "is to explore what motivated this singular artist and show how he has become even more relevant in today's world."

Their task is not as easy as it may appear on the flat surfaces which Magritte so carefully worked up. Look at his work and you are struck by two things. One is the directness of the imagery. The other is the way that they are composed to confuse and disorientate you. A view of a landscape through a window in La Condition Humaine of 1933 is partially obscured by a painted canvas of exactly the same view hidden behind it. The landscape is both within and outside the room.

"Visible things always hide other visible things," as Magritte put it, implying that the landscape itself may be only a canvas hiding something unknown beyond.

That is Magritte and his fellow Surrealists, endlessly playing with reality and illusion in an effort to break your assumptions about the solidity of objects and, in Magritte's case, to arouse in you a sense of the mystery of things and thought. A host of bowler-hatted men in Golconda of 1953 hang in space along geometrically arranged lines across a streetscape, as if they were rain, only whether they are rising or falling is an open question. A train comes out of the fireplace beneath a clock in Time Transfixed of 1938, only the train is going nowhere and the mirror is largely blank – time- and motion-less. The nude figure of a woman is imprisoned in a glass bottle that confines her flesh in its straight, glassy lines in Bottle-Woman (1945). A man paints a bird with flapping wings in Clairvoyance (1936) while actually looking at an egg. A meal with wine and fruit is recalled in Souvenir de Voyage, only the fruit and table are petrified as rocks and the doors open up not to field and sky but a wall of real rocks. The Intimate Friend from 1960 is seen, bowler-hatted again, from the back, with the images of bread and wine hovering behind his back. A couple kiss in The Lovers of 1928, only with their heads covered in sheets. Most famous of all, a perfectly painted pipe in Treachery of Images from 1929 has the legend, "This is not a pipe", in the supreme example of Magritte's obsession with bringing words into the picture, not just as a comment on the painting but also as source of ambiguity and multi-meanings themselves.

Playful or just perverse, childlike or merely jejeune? What marks the Surrealists is their humour, their desire to surprise through playfulness. Only this jokiness, intended to disconcert, makes it – as it was intended – almost impossible to know just how seriously to take them or their compositions, how far to puzzle away for meanings in works that are meant to portray meaninglessness.

Of all movements, Surrealism was the most intellectual and wordy. Its progenitors were poets and philosophers as much as artists, endlessly discussing the meaning of meaningless in our existence. Indeed, for some of its leading proponents, painting had no real place at all. Even trying to represent objects in order to deny them was a form of affirmation of the real that didn't fit with their philosophy.

Forever changing partners and producing new manifestos, they held endless meetings to discuss new projects and whether to expel members for heresy in a two-decade-long performance that fitted every expectation of satirists, then and now.

Magritte split with André Breton, the self-appointed leader and main theoretician of the Surrealist movement, when at a dinner party in Paris in 1930, Breton loudly demanded that Magritte's wife remove the cross from around her neck as incompatible with the movement's anti-clerical principles. She got up and left. So did her husband. Breton and Magritte barely communicated for the next two years. But then Magritte, a few years later, was party to the expulsion of one of the Belgian group's leading musical members for agreeing to conduct an orchestra at a Mass.

Back in Brussels during the occupation, so his friend Marcel Marien recalled in his autobiography, Magritte and his brother made money by producing fake pictures by the masters as well as banknotes. True or false? Magritte was certainly proficient and knowledgeable enough to do it. Copying and passing off paintings as real was well within the code of Surrealism. But then there's no evidence that it actually happened.

Paradox was the fundament of Surrealism and Magritte was the most paradoxical of all its proponents. He presented an entirely respectable bourgeois front, happily married, living in the more salubrious parts of Brussels and painting not in a studio but a corner of the living or dining room. Yet his whole life was spent subverting the bourgeois and their values. A man who made his living for a time designing wallpaper and illustrating fur-coat catalogues, he expressed contempt for his past as a commercial artist and attacked their values in the harshest terms. The painter who best understood that a picture is worth several hundred thousand words spent much of his time trying to explain them in words not just on the canvas but through letters, speeches, essays and tracts. An artist who was perfectionist in his portrayal of objects, he kept denying the value of a painterliness of which he himself was master.

Of all Surrealists, Magritte was the most collegiate, hugging close the Belgian group of which he was a member at its founding in 1926 right until the end of his life in 1967. And yet, in most ways, he was a loner as an artist, at the fringes but never fully accepted in the centre of the international Surrealist movement in Paris.

This was partly – mainly, perhaps – because he was Belgian. The major painters who gathered in Paris – Salvador Dali, Joan Miro, Max Ernst, André Masson and Yves Tanguy – came from all parts of Europe, especially Spain. But they gathered in France under the aegis of the writers Breton and George Bataille. Magritte settled there for a couple of years between 1927-30, in the first flush of his Surrealist ardour. Although he made good friends, wrote and produced illustrations for the main periodicals and attended meetings, he never broke through in Paris. His first one-man show there wasn't until after the Second World War and then he expressed contempt for the city of his youthful dreams by showing a collection of brutal pastiche works of French artists, in his co-called Vache Period.

French snobbery against the Belgians – always a recurrent theme in Parisian circles? That certainly played a part. But it was also that Magritte, coming from a bourgeois background in such a bourgeois country with so unsettled a history as Belgium, absorbed both its sense of "correctness" and insecurity, and reacted against them. He was a teenager when his motherland was first occupied by the Germans and into his forties when they did so again. Magritte always stayed intensely loyal to the country of his birth and his circle there.

He remains something of a mystery, despite the number of letters he wrote and friends he made. Much has been made of the suicide of his mother when he was only 13. The story went that he saw the body of his mother dragged from the river where she drowned herself, and that the image of her face covered by the wet nightdress in which she had gone out remained with him all his life and accounted for his repeated use of clothed faces. That may be so, although diligent research in the manner of our academic times has produced no evidence that he actually saw the body's recovery.

The death of his mother, who had been depressed for some years and was kept locked in her room for most of the time, must have affected him. Great screeds have been written by psychiatrists and would-be psychologists explaining how this experience accounted for the peculiarities of his vision.

Much of this seems the usual tosh written by psychiatrists when trying to analyse the creative process. You don't need personal tragedy to explain Surrealism and their Freud-inspired interest in the unconscious. What marks out Magritte is not the passion behind his work but the formalism of his art and the fragility of his feeling. From the start he approached art as a means of articulating his view of life as something elusive, disturbing and mysterious.

"They want to revolutionise art," he later said of young artists, "I wanted to break free from it." He did this first by trying out Cubism and the experiments of Braque and Picasso in viewing objects from the inside out and then by dabbling in Dadaism, with its notions of the absurd and the essential alienation of man. His moment of epiphany, however, came when he saw a reproduction of de Chirico's Love Song, a masterpiece by the Italian godfather of Surrealism in which the mundane and the artificial are mixed with the human and the organic to create an impression of timelessness and mystery.

It was the mystery, the sense of wonder, that attracted Magritte and made him so different from most of his fellow Surrealists. Where Joan Miro espoused the "automatic" approach, letting the unconscious determine the line, and Dali reached into the dreamworld, returning to three-dimensional and figurative art in his later work, Magritte kept rigidly to his canon of flat dimensions and frozen images. What he wanted, and what he achieves in his best work, was not so much to challenge the viewer as to intrigue him into seeing life liberated from the concrete and the present.

Magritte wanted to puzzle the onlooker, hence his wordplay, but he also wanted to cheer his audience. His reaction to the German occupation of Belgium in the Second World War was to break out of his traditional style into using Impressionist brushwork on the grounds that, in the days of darkness, people needed to feel joy. His reaction to the end of the war was to explode into his Vache period, when his images became almost comic in their extremes

It didn't work for the gallery owners or for the audience, and Magritte soon returned to a more sober style, but also a more ethereal one. His later works have a poise, a serenity indeed, that suggest that the artist had achieved a comfort with what he was doing. Home movies and, at the last, sculptures took his new fancy but the images he favoured remained the ones in paint.

The Tate Liverpool argues that the reason for reviewing him now is that he has become more relevant than ever. That is true in artistic terms. Where would Gilbert and George or half the sculptors working today be without his influence? The Surrealist belief that an inanimate object is as human as an organic, that the world of appearance is also the world of disguise, and that image is the mechanism for understanding the many levels of reality, are the commonplace of pop and conceptual art.

What is lacking is Magritte's sense of doubt opening up to wonder, and wonder opening up to doubt. It's what makes Magritte so popular with the public. He may confuse but, unlike most of the other Surrealists, he doesn't set out to tell you things but to lead you out of them into a freer vision. He's on your side.

Not that he isn't complicated and elusive at times. Although he was much praised by the pop artists of the post-War period he was somewhat dismissive of them. "The humour," he said in a television interview, "of Pop Art is rather 'orthodox', it is within the reach of any successful window-dresser; to paint large American flags with one star more or less does not require any particular freedom of mind and does not present any technical difficulty."

The irony for Magritte is that it is because his images seem within the reach of the successful window-dresser that he is so well known. We don't need a big new show to confirm a reputation long since risen from the margins of critical theory and Modernist dismissal. But we do need one that displays the "freedom of mind" and the mastery of "technical difficulties" he struggled so persistently to achieve. If by presenting his works in their full variety and through thematic display (as it is doing) the Tate Liverpool can bring an audience to feel that ambition then it will have served its purpose.

"We must not fear daylight just because it almost always illuminates a miserable world," he once said. That is what gives René Magritte his real relevance today.