Joseph Kosuth's "One and Three Chairs" (1965). In this piece, Kosuth displays a photograph of a chair, an actual chair, and a dictionary definition of the word "chair." The piece distinguishes between the three aspects involved in the perception of a work of art: the visual representation of a thing (the photograph of the chair), its real referent (the actual chair), and its intellectual concept (the dictionary definition). Reality, image, and concept: the three "sides" of a perceived thing.