appearance. The actual oak tree is physically present, but in the form of a glass of water." and "It would no longer be accurate to call it a glass of water. One could call it anything one wished but that would not alter the fact that it is an oak tree." The impossible is deliberately asserted and the text examines the impossibility of the assertion, which uses the idea of transubstantiation in the same way as the Catholic religious belief that bread and wine, while maintaining an unchanged appearance, are changed into Christ's body and blood. Craig-Martin has a Catholic background and was an altar boy. He sees belief of both artist and viewer as having a key place in art, and that in An Oak Tree he had "deconstructed the work of art in such a way as to reveal its single basic and essential element", namely this belief. An Oak Tree was a turning point in his artistic development: prior to it his concern had been deconstruction, and afterwards he was "trying to put the pieces together again." Subsequently, using the rationale of Marcel Duchamp's Fountain, he worked with drawings of utilitarian objects and flat areas of colour, with the goal of discarding meaning, which is "both persistent and unstable", although he states that people's need to create associations and meanings makes this goal unachievable. History An Oak Tree was first shown in an exhibition of Craig-Martin's work at the Rowan Gallery, off Bond Street, London, in 1974. Many visitors assumed that Craig-Martin was playing the ultimate con trick, as there seemed no evidence of work on display in the white-walled gallery. However, high up on a wall was the glass of water and the glass shelf of the work An Oak Tree. At this time the accompanying text was available as a leaflet. The original was purchased by the National Gallery of Australia in Canberra in 1977; an artist's copy has been on loan to the Tate gallery in London from a private collection since 2000. Craig-Martin said, "An Oak Tree has had a great life as an artwork. It is nearly always on view somewhere, and has been shown all over the world—the text has been translated into at least 20 languages. The only place it has never been shown is in the US." It was once barred by Australian officials from entering the country as