An oak tree

Q. Do you mean that the glass of water is a symbol of an oak tree?
A. No. It's not a symbol. I've changed the physical substance of the glass of water into that of an oak tree.

Q. It looks like a glass of water.
A. Of course it does. I didn't change its appearance. But it's not a glass of water, it's an oak tree.

Fabulosa, esta obra de Michael Craig-Martin no a vida é larga. Se entendo bem, o post reproduz o texto escrito no papel que se vê na fotografia.