Introduction

In March 1597, Johannes (1571–1630) published his first work, Mysterium cosmographicum, at Tübingen. Unknown to most of today’s readers, this title is abridged from “The forerunner (prodromus) of the cosmographical essays, containing the Mysterium cosmographicum [. . .].” What did Kepler mean by the word “forerunner”? In the revised edition of 1621, he explained:

Forerunner.] After I came to the study of philosophy in my eighteenth year, in the year of Christ 1589, the Exotericae Exercitationes of Julius Caesar Scaliger was passing through the hands of the younger gen- eration; and taking up the opportunity offered by that book, I began to devise various views on various questions—on the heavens, on souls, on characters, on the elements, on the nature of fire, on the origin of springs, on the ebb and flow of the sea, on the shape of the continents of the , and the seas that flow between them, and the like. But since the discovery of the proportion of the heavenly spheres seemed to me outstanding, I thought I should not wait until I could traverse all the parts of nature, and that this discovery should not be published incidentally, thrown onto a pile of other inquiries, achieving but a slight probability. Rather, I decided to make the publication of this discovery the starting point of my dissertations and dared to hope for a similar success in all the remaining inquiries; but in vain. For the heavens, the prime of the works of God, are much more notably embellished than the rest, which are pal- try and mean. While the forerunner was, indeed, excellent, the intended successors did not follow, because in the remaining inquiries I did not achieve anything which was equally satisfactory. However, the reader will be able to have my astronomical works, and especially the books of the Harmonice [mundi], as the authentic and appropriate successor of this little book [. . .].1

Kepler had originally planned to expand his research to the terrestrial region and to present his findings in a series of “cosmographical essays.” However, as

1 Kepler, Mysterium cosmographicum, 2nd ed., in Gesammelte Werke, 8:15, trans. Duncan, 51 (slightly modified). On the date of printing for the Mysterium cosmographicum, see Voelkel, Kepler, and the New Astronomy, 38. Kepler also recorded his enthusiasm for the Exercitationes in the autobiography that he wrote in preparation for drawing up his own horoscope. See Kepler, Gesammelte Werke, 19:329: “In physica Scaligerum suspexit.”

© koninklijke brill nv, leiden, ���6 | doi ��.��63/9789004310100_002 2 Introduction he explains, this plan failed because, in comparison with his investigation of the superlunary realm, the exploration of the sublunary world yielded unsatis- factory results. Consequently, Kepler devoted himself to astronomical studies, a field in which his achievements would be significant. Scholars have explored Kepler’s astronomical discoveries and their impact on the history of astronomy extensively.2 By contrast, the young Kepler’s moti- vation to study nature has received little attention. Although Kepler clearly states his initial investigation’s indebtedness to the Exotericae Exercitationes of Julius Caesar Scaliger, the question of how Scaliger’s work affected Kepler’s conception of nature has not been addressed to date. Existing studies focus on the lectures Kepler attended at the Lutheran University of Tübingen as intellectual context for his basic concept of the world. Although many ideas found in his works have thus been elucidated, some aspects of his natural phi- losophy remain unexplored. Most intriguing is Kepler’s remark that he first thought about the planetary revolution in terms of Scaliger’s theories in the Exercitationes. The lack of an investigation of Scaliger’s treatise in relation to Kepler’s writings has therefore deprived us of the opportunity to reflect on the origins of Kepler’s astronomy. It is here worth noting Francis Yates’s desideratum of some forty years ago: “Has anyone really explained where Kepler, Newton, Galileo, came from? I wish that a concerted effort could be made, less on the published writings of the great in their modern and accessible editions than on the vast sleeping tomes.”3 The Exotericae Exercitationes of Julius Caesar Scaliger is one of these tomes, and the present study is an attempt to respond to Yates’s suggestion by examining this still “sleeping” work. Julius Caesar Scaliger, the author of the Exotericae Exercitationes, lived from 1484 to 1558.4 In his autobiographical records, Scaliger claimed that he was the last descendant of the Della Scala (Scaliger) family, which had once ruled Verona. According to Scaliger, after William Della Scala (the last prince of the family) had lost control of Verona, his grandson Benedetto had entered into the service of the king of Hungary, while his wife and a son stayed at the castle of La Rocca at Riva. When Benedetto’s wife gave birth to Julius Caesar in 1484, the castle was under siege by the Venetians, who wished to extinguish the line of Scaliger. Both the mother and the two sons barely escaped with their lives. Since they had lost their home, the family stayed at the court of Maximilian I

2 See an overview in Bialas, “Astronomie,” 906–19. 3 Yates, “Hermetic Tradition,” 271. On Kepler’s Tübingen years, see especially Methuen, Kepler’s Tübingen. 4 My account of Scaliger’s life relies on Hall, “Life of Scaliger”; Billanovich, “Benedetto Bordon”; Jensen, Rhetorical Philosophy, 15–49.