Why shouldn't a vase be as beautiful as a picture?

THREE vessel shapes have been roughly carved and sliced out of solid greyish clay. Their creator, Tony Cragg, an aesthetician of waste and garbage, has always maintained that sculpture's principal responsibility is to give greater resonance to things and materials. His poetic piece is a modest resolution of this aim and one of the best things in a show full of beauty. The Raw and the Cooked, at the Barbican in London, attempts something difficult, the dismantling of hierarchies by showing the work of potters and sculptors side by side.

'Why should not a porcelain vase be as beautiful as a picture?' asked the potter Bernard Leach in 1911. He was then a young painter and etcher living in Tokyo, a member of a set of wealthy Japanese intellectuals and artists passionately absorbed by the European avant-garde but also engaged in a process of inverse Orientalism through a study of Zen aesthetics, the cult of Tea and the vernacular arts of Korea. Soon after posing his question Leach read Clive Bell's Art. There he found an outline of modernism in which Sung vases, Chartres, Mexican sculpture, Giotto frescoes and the paintings of Piero, Poussin and Cezanne stood together on an equal footing.

All great art, Bell argued, had a 'universal and eternal' appeal and could be appreciated without special knowledge or the experience of connoisseurship: 'If the forms of a work of art are significant, its provenance is irrelevant.' The magnificent democratisation of art outlined by Bell was generous to all the world's art and put spontaneity and truth to materials before the relentless trade skills of the 19th century art world. Bell's ideas filled Leach with hope and reflected his catholic experiences in Japan. Why should not a porcelain vase be as beautiful as a picture?

This was one of modernism's more fragile constructs. For a springtime-period, handblock printed textiles, monumental pots carrying abstract marks and directly carved sculpture represented some kind of unity of art, craft and design. Artists turned their eyes to everyday objects, to 'things'. For instance, in a letter of 1924 detailing influences on his work, the poet Rilke put his intimacy with Rodin and his love of the work of Cezanne in second place. The real decisive encounters had been with artisans - matching the repetitive work of a rope-maker in Rome and of a potter in a small village by the Nile. And ceramic in the 1920s, with its marvellous tactile potential and its therapeutically enclosing brand of formalism, appeared an inclusive art that synthesized high art, archetypal shapes and the repetitive actions of Rilke's humble Nilotic potter.

Since those first optimistic decades of the 20th century, ceramics, defined narrowly as 'craft', has been caught uneasily between two modernisms - the modernism of fine art, uncertain and chaotic, and the modern movement in design with its disciplinary certainties. If today the art of ceramics is mostly buoyed up by a devoted amateur following and by a discerning band of collectors, it none the less remains isolated. Fine art critics tend to be wildly misinformed, invariably taking pottery as an exemplar of qualities like skill and tradition. The exhibition at the Barbican is, therefore, cause for rejoicing. The great potters of our time are on show in the company of a handful of sculptors in a gallery firmly associated in the minds of the public with mainstream art activities.

In fact the contribution from the fine art world seems a little thin - apart from Tony Cragg's handsome tribute made at that epicentre for boundary crossing, the European Ceramics Works Centre in the Netherlands. Bruce Mclean, surrounded by so much grave beauty, emerges as a pasticheur whose foray into ceramics looks coarse. Anthony Gormley's Twenty Four Hours, a scuttling, morphic Ascent of Man almost topples over into another vulgarity, one of ideas rather than workmanship. Other unclassifiable artists prove more interesting. Bryan Illsley, jeweller/ painter/ creator of collaborative books, Stephanie Bergman, painter/ textile/ artist/ ironic apron-maker, and Jacqui Poncelet, potter turned sculptor, all in different ways understand something about clay at a profound level - its responsiveness to touch (Illsley), its capacity for austere moulded limitations (Poncelet).

And there are problems with this show which are mainly to do with this particular fin de siecle, a time of retrenchment and artistic caution. There is a marked conservatism of ambition in which clay is tamed rather than allowed to declare its inchoate, messy qualities. Looking through a catalogue of a comparable show put on 15 years ago, State of Clay, images of excess and optimistic sculptural experimentation abound.

At the Barbican, on the other hand, there is a good deal of well-made, well-mannered commentary on ceramic history. In pieces by Richard Slee, Carol McNicoll, the late Angus Suttie and Philip Eglin, this commentary attains a kind of anarchic playful seriousness that is rich in the kinds elevated ironies we associate with mannerism. At its least successful such work merely seems genteel.

Perhaps the greatest satisfactions in this exhibition are provided by artists who in different ways allude to that springtime of modernism experienced by Leach, to a period when the pursuit of pure form stripped away historicism. Simplicity equals strength. There is Ewen Henderson with his towering magaliths, Gordon Baldwin's remarkable marriage of abstract painting and sculpture, and Gillian Lownde's spare carapaces. There is Sara Radstone's austere minimalist stoneware and the work of young Lawson Oyekan whose tall, casually-built vessels celebrate freedom and spontaneity.

Finally there is Gwyn Hanssen Pigott. She is the one potter in the show who belongs to that functional world represented at its best by the porcelain of David Leach or Joanna Constanides and at its worst by a badly designed stoneware brown mug. Piggott has grouped a series of porcelain bottles, bowls and beakers into austere tableaux. The idea, a trompe l'oeil commentary on the relationship between art and its objects, sounds familiar and shallow enough. But the simplicity and assurance of her work suggest, as much as anything in this show, those absolute, Platonic Ur-shapes and objects that underpin all attempts to recuperate purity in the visual arts. Faced with Hanssen Pigott's work and that of Baldwin, Henderson, Radstone, Lowndes and Oyokan, we can ask again, this time with more confidence, why should not a porcelain vase be as beautiful as a picture? Why not, indeed?