  A third sort of argument, more historically inflected than the first, takes off from an influential study by the historian of philosophy Paul Kristeller, in which he argued that the modern system of the five major arts [painting, sculpture, architecture, poetry, and music] which underlies all modern aesthetics … is of comparatively recent origin and did not assume definite shape before the eighteenth century, although it had many ingredients which go back to classical, mediaeval, and Renaissance thought. (Kristeller, 1951) Since that list of five arts is somewhat arbitrary, and since even those five do not share a single common nature, but rather are united, at best, only by several overlapping features, and since the number of art forms has increased since the eighteenth century, Kristeller’s work may be taken to suggest that our concept of art differs from that of the eighteenth century. As a matter of historical fact, there simply is no stable definiendum for a definition of art to capture.