ow best to define art is still regularly debated. Many books and journal articles have argued over even the basics of what we mean by calling something art. Theodor Adorno claimed, in 1969: "It is self-evident that nothing concerning art is self-evident." Artists, philosophers, anthropologists, psychologists, and programmers all use the notion of art in their respective fields, yet give it considerably different operational definitions. Furthermore, it is clear that even the basic meaning of the term "art" has changed several times over the centuries, and is continuing to evolve during the 20th century as well. Most people would not have considered the depiction of a Brillo Box or a store-bought urinal to be art until Andy Warhol and Marcel Duchamp, respectively, placed those objects in the context of art (i.e., an art gallery), which then associated these objects with a way that art could be defined.