Lee is the third East Asian artist to be showcased in a major Guggenheim career retrospective after fellow Korean Paik Nam-june in 2000 and Chinese contemporary artist Cai Guoqiang in 2008. Born in a mountain village in South Korea in 1936, Lee studied and worked in Japan. As a sculptor, painter and essayist he was an important figure in the Japanese Mono-ha movement in the late 1960s and 70s. Mono-ha, which means 'school of things', uses the often-obscure philosophy of Martin Heidegger and the modern Buddhist ideas of the Kyoto School to posit a new theory of art.

Art is generally about expression: through their work artists are expressing their views about the subject before them. Mono-ha rejects this idea of the artistic process: Lee says he does not comment on his subjects at all. In fact, he says, his work is devoid of personal expression. His work is about revealing what is there, rather than commenting on it, he says. If he presents a stone as part of his artwork, he intends it to be just that: a real, individual stone. 'Expression is not almighty for me,' Lee says at the opening of the US exhibition.

If all this sounds theoretical, that's because it is. Like most conceptual art, Lee's sculptures become more interesting when the ideas behind them become known. The artist has concentrated on long series of works which have taken place over years. His Relatum series, works of which are on show at the Guggenheim, is the most famous. The works in this series consist of rock and/or steel plates arranged in different spatial configurations. The spatial arrangement is of primary importance to Lee, says curator Munroe. Artworks often have a focal point, a centre to which the eye automatically gravitates. But Lee's works are designed to be viewed from any perspective.

This is the way that Lee expresses his political philosophy, Munroe says. 'In a post-modern, post-colonial world, there is no longer a defined centre. It is a de-centred, multi-polarised world. We have moved from a world containing fixed socio-political hierarchies to a world where everything is becoming decentralised. There are now many different centres.

'Lee understands this, and that is why his works do not have a specific centre. They are democratic in the sense that you can look at them from any point of view.'

Out of this comes one of Lee's most important metaphysical ideas, says Munroe. 'As there is no hierarchy in Lee's work, man is no longer at the centre of the world. His works are models of co-existence. Man is co-operating with nature. The viewer, the location and the stone are all equal. Man is reduced to an equal player.'

The public is probably more familiar with Lee's paintings as many have been auctioned in recent years. At first glance, his two-dimensional works could be confused with the work of the abstract expressionists. Series such as From Point and From Line were created by passing or dotting the brush on the canvas until it was empty of ink or paint. The works are abstract, and Lee seemed to have paid attention to colour and texture.

But the intent behind the works is the opposite of those by abstract expressionists such as Jackson Pollock, Munroe says. 'Pollock is painting his psychological self. He is painting his psychological experiences. But Lee's work does not express anything about himself. It's trying to show what is outside. He is void of expression. He sees himself as a medium for something that is bigger and outside of himself. Lee is restraining his creativity, he is restraining his expressivity.'

The first Mono-ha artwork, 1968's Phase-Mother Earth by Sekine Nobuo, was a kind of happening, or event. The artist dug a hole, arranged the earth from the hole in a cylindrical shape, then filled the hole back up again. The idea of a happening is still important to Lee's work. For Relatum (formerly Phenomena and Perception B), the artist dropped a stone on a piece of glass in the Guggenheim. The glass cracked on a rolled steel plate below. 'The action of breaking was very important,' Munroe says. 'He insisted on doing it himself. In fact, he hurt his back and had to go directly to an acupuncturist. He lifted that rock and dropped it. It was very loud.

'There was a moment of tactility when it hit,' Munroe continues. 'At that point, the property of each of those things became momentarily united. The break made, and makes, them interconnected. Art for Lee is about contact with time and space.'

Lee's work is sometimes said to have transcendental qualities. The word 'transcendental' in art is usually used to denote religious or spiritual qualities. The viewers' experience of the work becomes greater than the art itself, and transports them to a higher spiritual realm. Munroe says Lee's work is transcendental in a different way: 'There is a transcendental quality to his art, especially his later works made in the 1990s and 2000s. But he never uses the word transcendental. He uses the word 'infinity' a lot, which is why the exhibition title is 'Marking Infinity'. Lee's concept of transcendental does not include any god. He definitely does not have any religious or specified spiritual practice, or adhere to any school or ideology.'

But Lee does have a specific and meditative philosophical approach to human existence on this earth, says the curator. 'It all revolves around the notion of infinity, which is the space-time continuum that is constantly repeating, constantly in a state of flux. It is filled with stuff, and it is our contact with this stuff in the time-space continuum that makes us human, that gives us our humanity.'

Lee Ufan: Marking Infinity, Solomon R. Guggenheim Museum, 1071 Fifth Avenue, New York, until Sep 28.