Magritte: “This is not a pipe”. Duchamp: “Really?”
The Treachery of Images (La trahison des images, 1928–29) is a painting by the Belgian René Magritte which, among other things (cf. Foucault) shows the inherent limitations of resemblance, i.e., reminds us just how limited our ability to apprehend the object actually is. Our categorization of a really existing object with specific physical qualities is based on habit, custom, & experience, & not because the object is the actual essence we give it (i.e., this object we call a pipe, because it was made in the manner that it was, facilitates the act of smoking but can never be wholly defined as being that & only that). Thus the statement “this is not a pipe” doesn’t negate the actually existing object that is depicted in the painting but rather the essence that we have given it. A pipe is a pipe is a painting of a pipe is a readymade & can be packed with tobacco.