It was famously said that sculpture is what you bump into when you back up to look at a painting. Although only a quip, it is not a bad definition of modern sculpture. Most modern sculpture - and its sidekick, installation - occupies space in a quite aggressive way. The artwork-as-obstacle was given clear expression in the introduction to American Sculpture of the Sixties (1967), a survey that included Carl Andre and, as an honorary American, Anthony Caro: "Sculpture here comes at you from all directions - from the ceiling and wall, or it may snake around a corner. When it rests on the ground, it doesn't really rest, but it still comes at you; it never reposes on a pedestal." Sculpture here was not only something that you might bump into; it was something that turned you into a pinball.
It wasn't always thus. From the Renaissance until the 19th century, statues tended to be placed flat against walls or in niches that neatly framed them. Viewers were expected to contemplate them from a relatively fixed position, as if they were pictures. This is borne out by the so-called "Medusa topos", the highest form of praise for a statue. Medusa was a mythical monster, and one look at her turned the viewer to stone. The conceit had it that the viewer, rooted to the spot in amazement, was more marble-like than the statue. In a poem written when Michelangelo died in 1564, Laura Battifera degli Ammanati said that the sculptor "overwhelmed whoever saw his works and left them as if petrified". Only one of his surviving statues was meant to be circumnavigated. All the others were designed to be placed against walls, in niches or on tombs.
Benvenuto Cellini, who created a celebrated bronze statue of Perseus and the Medusa, was quite clear about the etiquette of viewing. Even a free-standing statue in the round had to be seen in a measured way, by a motionless viewer. Cellini recounts how Duke Cosimo I of Tuscany came to see his model for the Neptune Fountain. He "walked round it, stopping to inspect it from all four sides just as an expert would have done". This choreography was socially determined: random circumnavigation did not befit the status of a gentleman or aristocrat. One's position was, so to speak, set in stone.
Modern ways of seeing go hand in hand with social revolution. In the 1780s and 1790s, English theorists of the picturesque proclaimed the superior virtues of anything that was wild, irregular, angular and down-to-earth. Picturesque art features ruins and fragments, peasants and workers. Although most of the early picturesque art was rather timid and sentimental, it did little to stimulate a shift away from highbrow and high-class subject matter. There was a corresponding change in the physical construction of artworks, and in the way in which they were viewed. The picturesque artist was encouraged to use an appropriately rough-and- ready technique, and viewers were encouraged to examine artworks in a less formal way, almost as though they were in a workshop. There was a cult of the workmanlike.
Thus, when the Elgin Marbles were bought by the British Museum in 1816, they were exhibited in their fragmented state. In a series of letters addressed to Antonio Canova, the French sculptor cum connoisseur Quatremere de Quincy explained that, whenever sculpture is integrated into architecture, it loses its grandeur and specificity, because the viewer is compelled to take in the whole building. But in the British Museum, the Elgin Marbles were displayed at eye level, in an unrestored state. It was like being "on the building site or in the studio itself", because the objects "are to hand in their actual dimensions; you can move around each one, counting up the fragments, assessing relationships and measurements".
A very similar phenomenon can be observed in relation to interior decoration. Before the 19th century, furniture was placed against the walls when not in use, so that the floor remained uncluttered. As a result, the backs of upholstered chairs were often left uncovered (just as the backs of sculptures were often left unfinished). But picturesque taste made it acceptable in England to distribute furniture around fireplaces and in the middle of rooms. A French visitor in 1810 commented that the apartments of fashionable houses looked "like an upholsterer's or cabinetmaker's shop". So England in the 19th century really was the workshop of the world.
The corollary to this was that there was less of an onus on the artist to repress the workmanlike aspects of his trade. Rather, there was an incentive to play them up as much as possible, and to find new ways in which to emphasise the artisanal. There was a spiritual dimension to all this. Thomas Carlyle asserted in Past and Present (1843) that "true work was worship". The Victorians made much of the fact that Christ was brought up in a carpenter's shop - Joseph being a carpenter by trade - and they insisted that, in heaven, we carried on working. So busy did heaven become that, by 1901, a baptist pastor in New York could reliably report that "practically it is a workshop".
Even schools aspired to the condition of workshops. It was increasingly assumed that a wholesale education of the senses was necessary before children could begin to read and write. Manual work, physical exercise and constructional toys were central to the curriculums of the international kindergarten movement. At the beginning of the 20th century, the Italian educationalist Maria Montessori developed a classroom that contained movable furniture and fittings adapted to the scale and needs of children. This was in contrast to normal schools, where the children sat at desks facing a blackboard, chanting in unison the words of the teacher.
Tactile education was central to the Montessori method. The child had to pass his or her fingers over wooden boards to which rough and smooth strips of paper had been glued, and feel different types of fabric and fastening. Writing was taught by using stencils and by touching sandpaper letters and numbers. The child also inserted geometrical objects into the correct slots, thus getting a sense of the volume, weight and shape of an object, and of the space it occupied. All these exercises were repeated using blindfolds.
Cubist collage and construction - with its extraordinary range of media, textures and edges - was the first great art form of the era preoccupied with the education of the senses. A Montessori school opened in Paris in October 1911, with the evocative name, La Source. There was extensive press coverage about the school and about the method from 1911-13, the most important years for the development of cubist collage and construction. Picasso and Braque regularly wore blue mechanics' outfits, and worked together as "collaborators" until their paintings became almost indistinguishable. They even gave up signing their work on the front of the canvas, and got Boischaud, the assistant of their dealer, Daniel-Henry Kahnweiler, to sign for them on the back. The only form of writing that appeared on the front of the canvas was stencilled letters or newsprint.
It wasn't too long before their art started to take a three-dimensional turn. Braque was probably experimenting with paper sculpture in the summer of 1911 because, in September of that year, he wrote to Kahnweiler saying how much he missed "the collaboration of Boischaud in making my painted papers". The following year, Braque added sand and metal filings to his paint and simulated the appearance of wood grain and marbling with a decorator's comb. He also incorporated stencilled letters and numbers. Braque was particularly concerned with the tactile qualities of his work. He put his interest in still life down to the fact that this genre dealt with objects that are within reach of the human hand: "I began to make still lifes above all, because in nature there is a tactile space, I would say almost a manual space." Braque went on to say that he had always had a desire to "touch the thing and not only to see it". The cubists referred to this type of work as a tableau-object - an object painting.
The cubists' down-to-earth approach to art-making was further emphasised by the way in which the canvases in their studios were casually laid on the floor, and placed on chairs and other pieces of furniture. There was no ideal viewing position for these pictures. Their constructions and collages also required an "engaged" viewer who was prepared to peer at their creases and into their crevices. Thus the cult of the worker-artist made new demands on the viewer, as well as on the artist. With cubist painting and sculpture, the Medusa topos effectively bit the dust.
This down-to-earth orientation is also central to the Montessori method. According to the American Dorothy Canfield Fisher, the method's field of operations was similar to that of the kitchen, the principal home of still-life objects and the place where most of the domestic manual work gets done. Writing in 1912, she praises the kitchen at the expense of the drawing-room - and of the museum: "We all know how much more fascinating a place our kitchens seem to be for our little children than our drawing-rooms . . . the drawing-room is a museum full of objects . . . enclosed in the padlocked glass-case of the command, 'Now don't touch!', while the kitchen is a veritable treasure house of Montessori apparatus." Cubist still life was also meant to be the antithesis of the "padlocked glass-case" kind of art.
The minimalist sculptor Carl Andre is a major exponent of these tendencies. Clad in overalls, he has made much of his experience working on the railways as a freight brakeman, of his bricklayer grandfather and of playing, as a child, in the workshop of his plumber father. His sculpture comprises geometric arrangements of concrete, brick, stone, metal and wood, with a variety of finishes. Direct physical involvement with a variety of materials, by both the artist and the viewer, is emphasised. The viewer is expected to walk across and stand on the metal plate sculptures (although the neophyte is just as likely to trip over their edges), and become "sensitive to the properties of the material". He sees this process as a collaboration. Everyone becomes what Carl Andre calls an "artworker", because the work is not complete until someone "does artwork himself with that artwork".
The materials revolution, and the notion of the artwork-as-obstacle, is closely related to beliefs about modern urban civilisation. Numerous writers, such as Baudelaire and Freud, have seen modernity as a field of unexpected shocks and surprises. At every turn, the citizen is ambushed by a new sensory experience. The Montessori method is one of many attempts to prepare the citizen for every sensory eventuality: it offers training in shock absorbance. The bracing nature of modernity has been well described by the architectural critic Manfredo Tafuri. Tafuri believes that modern man has to learn "not to 'suffer' the shock [of modern civilisation], but to absorb it as an inevitable condition of existence". In other words, we have to embrace ongoing discontinuity and rupture.
This ideology is also pertinent to the work of the postwar German artist Joseph Beuys, who currently has a room in Tate Modern. Beuys's installations feature a wide variety of materials such as fat, felt, dead and live animals, wood, metal, glass. In an interview in 1986, Beuys spoke of the vital importance of shocks to the system. He insisted that without collisions, there is no such thing as consciousness: "It is clear that consciousness is impossible without death. It is only when I hit a sharp corner, so to speak, that I become aware. If I knock my head against a sharp edge, I wake up. In other words, death keeps me awake." Beuys is here echoing Ludwig Wittgenstein, who defined philosophy in similar terms: "The results of philosophy are the uncovering . . . of bumps that the intellect has got running its head up against the limits of language. These bumps make us see the value of discovery." No wonder we call avant-garde art "cutting edge".
The bumpiness of so much modern art is in part a wake-up call to those whose experience is mediated through "flat" technologies such as photography, the printed word and, more recently, computer screens. In the 1960s, Carl Andre regarded the camera as the most catastrophic invention of the modern age, and his contemporary Richard Serra has railed against what he calls "Xerox history". Not only did photography deny the temporal experience of the artwork, but also most photographs "take their cue from advertising, where the priority is high image content for an easy gestalt reading". The best modern art can now be thought of as an antidote to the disembodied sites of the dotcoms.
Carl Andre's first solo London exhibition since 1978 is at the Whitechapel Art Gallery (020-7522 7888) until 27 August
James Hall's book, The World as Sculpture (Pimlico, £15), has been shortlisted for the Sergio Polillo International Art Book Prize