“An oak tree” By Michael Craig-Martin was created in 1973. The installation is made up from an ordinary glass of water placed on a small glass shelve place just over head level. Below the self to the left is a conversation claiming the glass of water is an oak tree.

In the text Craig-Martin creates the argument that the single glass of water is actually a full grown oak tree. He makes it clear that naming the glass of water it’s self is not symbolic of anything and all he has done is change the glasses physical form.

This piece link very close to the story in the bible and the beings in transubstantiation, where the idea that the bread and wine are the body and blood of Christ even thought they have not a fully changed in appearance.

Transubstantiation definition is : the conversation of the substance of the Eucharistic elements into the body and blood of Christ at the consecration, only the appearance of the bread and wine still remain.

To simplify that it means : an act to change the form or character of something without changing its appearance.

Craig Martin started that “the oak tree only exists in the mind”.

This piece is at the heart of conceptual art, to be able to believe or see that the glass of water showing that the meaning doesn’t have to have anything to do with the appearance and it’s all what you believe it is. An oak tree had a religious metaphor which Craig-Martin believed. He thinks beliefs is purpose if are, he stated;