To be or  not be... a pipe

Ceci n'est pas un conte (Denis Diderot, 1798)
When one tells a story it is for a listener; and however short the story is, it is highly unlikely that the 
teller is not occasionally interrupted by his audience. So I have introduced into the narration that will
 be read, and which is not a story, or which is a bad one if you have doubts about that, a character
 that might approximate the role of the reader; and I begin.

Rene Magritte (1928-29)
The famous pipe. How people reproached me for it! And yet, could you stuff my pipe? No, it's just a representation, is it not? So if I had written on my picture "This is a pipe," I'd have been lying!

Ceci n'est pas un pipe (Michel Foucault, 1973)

"No matter that it is the material deposit, on a sheet of paper or a blackboard, of a little graphite or a thin dust of chalk. It does not 'aim' like an arrow or a pointer toward a particular pipe in the distance or elsewhere. It is a pipe."

This is a pipe (Bansky)