Leonardo da Vinci was an important source for eighteenth-century thinking about shadow, and he is also the first modem writer to offer a systematic view of shadow, as such: he addresses every objective kind of shadow and is still cited in the current literature (for instance, Koenderink and van Doorn, 1980). While his thought about vision in general clearly has a background in medieval and Renaissance optics, which has been well studied by Lindberg (1976) and others, his thought about shadow in …