High Quality Content by WIKIPEDIA articles! An Oak Tree is a conceptual work of art created by Michael Craig-Martin RA in 1973. The piece consists of two units; an object, a glass of water on a glass shelf, and a text. 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".