On the evening of 24 February 2000, Sol LeWitt took part in an odd event at Brandeis University in Massachussetts. Before a mesmerized audience, the artist pried open a box holding a work he had interred in it 25 years before. This turned out to be another box - a one-inch cube of white paper this time, which, when opened, revealed a diagonal line drawn across its bottom plane beside the words "A line not straight corner to corner", its maker's signature and a date, 13 October 1974. LeWitt, who had clearly forgotten all about the work, held it up to his face and frowned. Then he muttered the disapproving words "minimal art", and sat down.
This episode sums LeWitt up in various ways. Most obviously, it underlines his place in the development of conceptual art, a role so central that he is still (if not entirely accurately) known as "the father of conceptualism". In the 1960s, he had joined artists such as Joseph Kosuth in rejecting the abstract formalism of the critic Clement Greenberg in favour of work in which, as LeWitt wrote in a 1967 issue of Art-forum, "the idea or the concept is the most important aspect." "When an artist uses a conceptual form of art," he went on, "all planning and decisions are made beforehand. The execution is a perfunctory affair. The idea becomes the machine that makes the art." This meant, in effect, that materials and skill no longer mattered and that art could consist of a paper cube scribbled on with a biro, the biro-marks themselves, or even of the idea of such things. Although this thinking had recent precedents, notably in the early work of Robert Rauschenberg and the Fluxus group, LeWitt quickly became its most articulate exponent. In 1969, he published the conceptual equivalent of Luther's 95 Theses, although - LeWitt having recently been a minimalist - his "Sentences on Conceptual Art" numbered just 35. The first declared that "Conceptual artists are mystics rather than rationalists", the last, bafflingly, that "These sentences comment on art, but are not art." Critics reeled.
Oddly, LeWitt's entombment of his 1974 paper cube was not the first inhumation in which he had taken part. Six years earlier, in 1968, he had buried a steel equivalent of the work in the garden of a Dutch collector. Called Buried Cube Containing an Object of Importance but Little Value, this was widely seen as the artist's deadpan farewell to minimalism, a movement whose reliance on materials had become too baroque for LeWitt's purist tastes. In the same year, he made the first of his famous wall drawings directly onto the wall of a New York gallery. Instructed to paint over the work at the end of the show, the gallery's horror-struck owner refused. She insisted that LeWitt paint it over himself, which he did without demur.
As with his cubes, it is tempting to read this overpainting as a form of burial; to see the trajectory of LeWitt's art as a process of removal, of willed loss. By drawing on walls, he did away with the need for paper or canvas. He also made sure that his work would not - could not - last, permanence being altogether too material. One of his first jobs had been as a graphic artist in the architectural office of I.M. Pei in New York. Now, Le-Witt used the substance of architecture to cancel out the substance of art, leaving it in the realm of pure abstraction. Bound up in all this was a gradual erosion of the self in his work, a tendency that reflected an almost obsessive need for privacy. (LeWitt steadfastly refused to be interviewed or photographed, remarking, tartly, that he was "not Rock Hudson".) From 1968 on, his art was increasingly made by teams of assistants whom he would modestly credit to his own cost.
Instructions to these assistants were left intentionally vague - the note on the bottom of his 1974 paper cube is typical - and relied more and more on self-generating mathematical systems for their execution. Hexagons, geometric progressions and, of course, cubes, became the mainstay of LeWitt's practice. Not surprisingly, mathematicians loved him, seeing works such as six geometric figures in three colors on three colors and all their combinations (1978) as problems waiting to be solved. Less numerate members of the public found LeWitt's radical excision of human narrative sterile and scary, and liked him less.
This was, perhaps, based on a misunderstanding. Although his work seemed increasingly dry, LeWitt's removal of himself from his own picture suggested a certain vulnerability. Born in 1928, he was the child of Russian immigrants. His doctor father died when he was six, leaving him to be raised by his mother and an aunt in a small Connecticut town. It is tempting to see his art as that of a lonely child, insisting on being taken on its own terms and calling for complete devotion. Like mathematical equations, LeWitt's works can only be solved with the participation of a viewer, and this in turn imposes a kind of intimacy.
Nor was his exclusion of humanity ever quite as complete as he seemed to hope it would be. In 1987, he responded to a public commission by erecting a wall of concrete blocks outside a government building in Hamburg in Germany. To this structure - LeWitt disliked the term "sculpture" - he gave the entirely narrative name of Black Form: dedicated to the missing Jews. "Being Jewish," he explained, "I noticed the absence [in Germany] of Jewish artists and curators, Jewish bakers and candlestick makers." This, too, may explain something of the defensiveness of LeWitt's work, and of its underlying sense of loss.
Although Sol LeWitt may not have been conceptualism's sole parent, he was certainly among its founding fathers. The Young British Artists owe a particular debt to him. Martin Creed's Turner Prize-winning The Lights Going On and Off can be traced, via Michael Craig-Martin, to LeWitt's fascination with the insubstantial. So, too, can Keith Tyson's mathematically self-propagating Artmachine of the 1990s. LeWitt's attitude to his own posterity, though, was typically self-effacing and wry. "One understands the art of the past by applying the conventions of the present," he said. "And so one inevitably misunderstands the art of the past."
Solomon LeWitt, artist: born Hartford, Connecticut 9 September 1928; twice married (two daughters); died New York 8 April 2007.