Studies of Old Masters are often implicitly based on modern notions, which do not necessarily tally with ideas contemporary with their art. According to one such tacit assumption a work of art gains its status from the quality of the abstract pictorial composition made up of lines and colours. Whether discussing a medieval altarpiece, or a fresco by Raphael, it is customary to relate its artistic value to the abstract formal language into which the figures or narratives are translated, and not to the power of the visual illusion which is conjured up by the work of art. Referring to the ideas of art historians, critics and philosophers including Hogarth, Caylus, Goethe, Schnaase, Burckhardt, W
