  In a paper published posthumously in 2001, Frank Sibley contends that a “two-directional pull” is a pervasive feature of the practices and discourses of art, at least with regard to visual works of art such as the Mona Lisa. If a painting is a particular physical object, the work of art referred to as the Mona Lisa may or may not be a painting: “Perhaps it both is and is not, can be and need not be” (2001, 272). We are interested in the unique physical object, yet we also find that a copy can serve many of the same functions, including artistic and aesthetic ones. So either we have two distinct concepts of works of this kind, or we have inherited what Sibley calls an “uneasy composite or hybrid of two conflicting notions” (2001, 272).