An Oak Tree is a conceptual work of art[1] created by Michael Craig-Martin (born 1941) in 1973. The piece, described as an oak tree, is installed in two units – a pristine installation of a glass of water on a glass shelf on metal brackets 253 centimetres above the ground, and a text mounted on the wall. When first exhibited, the text was given as a handout.[2][3][4]
The text takes the form of a Q&A about the artwork, in which Craig-Martin describes changing "a glass of water into a full-grown oak tree without altering the accidents of the glass of water," and explains that "the actual oak tree is physically present but in the form of the glass of water." Craig-Martin considered "the work of art in such a way as to reveal its single basic and essential element, belief that is the confident faith of the artist in his capacity to speak and the willing faith of the viewer in accepting what he has to say".[3]
The Catholic Herald compared the work to the Roman Catholic doctrine of Transubstantiation and the Real Presence.[5]
The original is in the National Gallery of Australia, and an artist's copy is on loan to the Tate gallery.