From Emblems to Diagrams: Kepler’s New Pictorial Language of Scientific Representation by R AZ C HEN -M ORRIS Kepler’s treatise on optics of 1604 furnished, along with technical solutions to problems in me- dieval perspective, a new mathematically-based visual language for the observation of nature. This language, based on Kepler’s theory of retinal pictures, ascribed a new role to geometrical diagrams. This paper examines Kepler’s pictorial language against the backdrop of alchemical emblems that flourished in and around the court of Rudolf II in Prague. It highlights the cultural context in which Kepler’s optics was immersed, and the way in which Kepler attempted to de- marcate his new science from other modes of the investigation of nature. 1. I NTRODUCTION :T HE P LINIAN F RAMEWORK :F INE L INES AND A BSTRACT I DEAS I n his Natural History Pliny the Elder (ca. 23–79 CE) supplies an outline of the significance and power of painting through several stories and comments. He tells, for instance, of the Greek painter Apelles, who traveled to visit Protogenes, another famous painter, in Rhodes. When Apelles ar- rived there, Protogenes was not in his studio, but in his place an old woman watched over a ‘‘panel of considerable size on the easel.’’ 1 Apelles decided to leave his mark and painted ‘‘an extremely fine line in color across the panel.’’ When Protogenes returned to his studio, he recognized Apelles as the only painter who could have painted such an exquisite line. In return Protogenes This paper is part of an Australian Research Council–supported project, The Im- perfection of the Universe (DP0664046). Earlier versions were presented in the workshop Pictorial Means in Early Modern Engineering, 1400–1650, at the Max Planck Institute for the History of Science, Berlin, 26–28 July 2001, and at the Baroque Science International Workshop, University of Sydney, 26 September 2006. I want to thank the anonymous readers for their remarks and corrections. I am grateful to Timothy Krause and Erika Suffern, my copyeditors, for all their suggestions. Special thanks to Ofer Gal, Stephen Gaukroger, Liam Semler, and Zur Shalev, and to my best reader, commentator, and friend, Joanna Chen-Morris. 1 The story is in Pliny the Elder, 1976, 120–23 (Naturalis Historiae 35, x81–83). This celebrated story has received many interpretations through the years; one may note especially the following: Gombrich; Waal; Elkins, 1995. Renaissance Quarterly 62 (2009): 134–70 [134]