Fountain, Marchel Duchamp, Image from Wikipedia.
A few months back, I went to a talk by Jacques Rancière and W.T.J. Mitchell titled The Future of the Image. One audience member asked both presenters the difference between an object and an image. Mitchell gave a quick response - saying essentially that an object is something you hold, an image is something you see. Rancière's response was more nuanced. He said, and I'm paraphrasing, that an object is something of a certain size, whose use-value or function is recognized and understood, like a razor or a bowl. As soon as that use value is called into question, or becomes unstable or indeterminate, the object becomes an image. It is precisely through a displacement into indeterminacy that an image is created.
I immediately thought about Duchamp's Fountain.
Many interpretations of Duchamp's toilet stress the Dadaist conceptions of author and artist. "Since Duchamp, the artist is the author of a definition", says Broodthaers. Bourriaud writes "when Duchamp exhibits a manufactured object as a work of the mind, he shifts the problematic of the 'creative process', emphasizing the artist's gaze bought to bear on an object instead of manual skill." The focus here is on the change in the role of the artist.
If instead we follow Rancière's idea of image, the importance of Fountain is the way it clarifies the fundamental relationship between object an image. Duchamp took an object with a known use and positioned it within an art context, establishing a question around its use value - destablizing its meaning and thereby creating an image. With this reading, you could say the artist is not so much "defining" art, declaring "This Is Art", but rather dissembling - creating questions and uncertainty by displacing objects into images. Fountain not only changed the role of the artist, it also shifted the conversation to focus on the subjectivity of representation.