Kepler's Witch Read online

  Then the hammer fell once more. The archpresbyter of Graz, Lorenz Sonnabenter, dug up an old medieval tradition, one that had been practiced in theory only, and used it against the Lutherans, effectively shutting them down. The tradition had been designed to protect the livelihood of the archpresbyter of a place, so that the fees he charged for his ministry could remain constant. He could, quite legally, forbid the practice of any competing ministry that would undercut his own, and he used this right to prohibit any kind of ministerial practice by Protestants.

  In a letter to Herwart von Hohenberg dated December 9, 1598, Kepler wrote: “In the month of August the prelude to the tragedy took place. The archpriest officially prohibited our preachers from all practices of religion, the administration of the sacraments, and the consecration of marriages.” The Lutherans complained to the archduke, but he shrugged, saying that he had to protect his own Catholics as well as the Lutherans, and so, where his own devotion had led him before, now he would act because his people had requested it of him. On September 13, Ferdinand promulgated an order to dismiss the Lutheran preachers and to break the collegiate faculty, and that this had to be done in two weeks’ time. On September 20, the archduke “decreed that all ordinations be canceled, and then let go all the servants of the church and school in Graz and Judenburg, and that within fourteen days they must leave his territories and stay away forever.”9 On pain of death. The councilors of the city begged Ferdinand for a repeal of the banishment, but he refused, and on September 23 gave them only eight days to get out and never come back.

  The town tried to call for the Stände, the assembly of representatives, but there were floods that year, and only a few of them could get to Graz in time. Ferdinand then called out the troops. The city roiled, near riot, near rebellion, while the troops stood by silently, waiting, ready for slaughter. There was nothing else the Lutheran teachers and preachers could do, so they packed their bags and on the appointed day trickled out of the city, some to Hungary, some to Croatia. They left their wives and families behind, an act of vain hope, perhaps, trusting that because the archduke was young, he might be swayed by other voices and allow them to return. Kepler was among the banished and left with the others. In his letter to von Hohenberg, he wrote that somehow, in spite of all the persecution, he was still paid. As for the situation, there was not much anyone could do. The faculty at the school was told to hope for some change after the Stände, the council of representatives, met.10

  Only Kepler was allowed to return finally, which he did in October. “As for me,” he wrote, “I returned after a period of one month, called upon by officials of the archduke, who described me as exempt.” Apparently, Ferdinand liked him and was proud to have a scholar of Kepler’s growing reputation working in his duchy. He could return, not as a teacher in the Lutheran school, but as the district mathematician. After all, the great Tycho Brahe of Denmark had read the Mysterium Cosmographicum and liked it. He had even written to Kepler, inviting him to come to visit him in Prague. That fellow Galileo, down in Padua, had also written a letter praising it, one Copernican to another. But as nice as Kepler’s growing reputation was, it was more to the point that Kepler was a modest man and was known to be a modest man, a man who disapproved of the antics of his fellow Lutherans. “We see,” wrote Mästlin to Kepler, “with what raging fury the devil incites the enemies of the church of God, as though he wanted to devour it completely.”11 Kepler kept his own counsel on that point, writing in his diary: “I am just and fair toward the followers of the pope and recommend this fairness to everyone.”12 Kepler then petitioned the archduke for his exemption and received it. “His Highness is herewith granting, out of special favor, that the petitioner, notwithstanding the General Dismissal, shall be allowed to remain here. But he shall maintain appropriate modesty everywhere, so that this exemption will not be subject to cancellation.”13

  Oddly enough, the Jesuits may have had something to do with this. Although Kepler was a committed Lutheran and could never have accepted the Roman Catholic faith, he was on good terms with some of the fathers at the Jesuit college, for Kepler knew that Father Clavius and a handful of other Jesuits were some of the best astronomers in Europe. In September 1597, a few months after Kepler’s wedding, one of the fathers in Graz, Father Grienberger, came to Kepler at the behest of the Bavarian chancellor, Hans Georg Herwart von Hohenberg, an important man and one of the first of Kepler’s important patrons. No doubt, there was some hope on the part of the good father, and on the part of the chancellor, of converting Kepler to Catholicism, but it was a vain hope. Not an irrational hope, though, becauce one of the archduke’s teachers at Ingolstadt had been Johann Baptiste Fickler, a distant relative of Johannes Kepler’s.

  Fickler’s mother, Benigna, born on the last breath of the Renaissance, was one of the great women figures of the time. Like Meg More, the daughter of St. Thomas More in England, Benigna was a well-educated woman. Her father, a wealthy merchant in Ulm, had insisted she read law and theology, so she could write contracts and dispute theological questions. She could read and write Latin, and some said she was the best lutenist in town. Wanting children, she married very young, buried her first two husbands, and finally married Michael Fickler, Johann Baptiste’s father. Had she lived at a later time, she would most certainly have been accused of witchcraft, because one of her many accomplishments, like Katharina Kepler’s, was the knowledge of herbs and the making of potions.

  In his first letter to Herwart von Hohenberg, Kepler made a point of sending his greetings to his relative, which were passed on and returned with thanks. These letters were all sent by personal courier from Bavaria to the emperor’s court in Prague, and from there back to Graz by way of the archduke’s secretary, a Capuchin father named Peter Casal, and then back again along the same route. This set of events raised Kepler above the rest of the Lutherans quietly leaving the city and set up his later exemption and return.14

  But was Kepler right in assuming that if the Lutherans had only been less provocative, the archduke would have left them alone? Probably not. The land was itching for war, and young Ferdinand itched along with it. He had determined to rid the land of heretics, and that determination would embrace an astronomer or two. Besides, he knew that the Lutherans weren’t much better. Lutheran dukes and princes had merrily expelled Catholics from their territories, so why shouldn’t he? People of all stations, all classes in Germany and Austria, from kings to peasants, were tripping over their own piety. In some secret, unlit room in the human soul, they all wanted war. And eventually, they got it.

  Kepler’s own openness did not sit well with his fellow Lutherans any more than his stubborn Lutheranism sat well with the Catholics. The other teachers at the Lutheran school resented his exemption, wondering if he had compromised his faith along the way just to please the papists. He had certainly broken ranks with the other teachers by petitioning, but there was more to it than that. His beliefs, like his thoughts, were subtler than theirs. Some later scholars accused Kepler of indifference to dogma, but this too was unfair, for he did believe that there is but one truth, and he pursued that truth, which he identified with God, with all his heart all his life. Kepler had to go his own way, for the truth he pursued was inside his own conscience and did not float outside him among the dogmas of the churches. Sometimes he accepted the teachings of his church, and sometimes he did not, for he had to find the authentic truth for himself, and no one could find it for him. This meant that he could not accept the truth of others just because they told him to, no matter how authoritative they were. Neither armies nor pulpits could sway him by themselves, but only reason and faith.

  Kepler’s doubts about the ubiquity doctrine and about the sacrament had been paddling about in his head for years, since the days he had first studied at Maulbronn. Now they came to the surface. Perhaps unwisely, he confessed his doubts to the exiled church members, who were shocked and suddenly suspicious. Those who had envied his return and suspected him of compromi
se suddenly had new ammunition. The others merely shook their heads, wondering. None of them really understood him, though. His theological meanderings were well within the bounds of the Lutheran faith. Or so he thought. But differences over what constitutes the heart of the faith are often the source of schism and of heresy. Kepler never quite understood this for himself, but others did, and from that day on they watched him carefully.

  Once back in Graz, the hardest thing for Kepler to endure was the sudden loss of the church life that had kept him close to God. He felt the emptiness of the place—he missed the sermons; he missed the sacraments. There were preachers about still, tucked away in the castles of the various Protestant estates, but if any subject of the archduke were to ask for the sacraments, and if the preacher agreed, then that preacher could find himself on the road out of the archduke’s territories, which included all of Styria, or Upper Austria. Surprisingly, though the Lutheran school had closed its doors, the school officials had kept Kepler on, partly because they felt sorry for him. They even paid his meager salary, but offered him no raise. Like Jobst Müller, the school councilors were practical men who enjoyed Kepler’s growing fame, but did not understand his work and could see little value in it.

  Kepler thought about leaving Graz, about finding another post somewhere else, at some university perhaps, maybe even at Tübingen, though he couldn’t have known that the faculty there was set against him. But how could he leave? Barbara was attached to her inheritance, though Jobst balked at giving it to her. She had not yet seen a taler of her money from dear Papa. And the way things worked in Austria at that time, old Jobst, and not Barbara, was little Regina’s guardian. Regina had inherited some 10,000 gulden from her own deceased father, and Jobst, as head of Barbara’s household before she married Kepler, took control of it. After the wedding, Kepler received 70 gulden annually for Regina’s upkeep, as well as the proceeds from a vineyard and the use of a house. Old Jobst had been trying to estrange the girl from Kepler in every way he could, though everyone could see that her stepfather was devoted to her. For Kepler’s part, he would have missed his dear little stepdaughter if he had left town without her, because old Jobst, as her guardian, would have kept her with him. Most of all, however, he worried that she might fall under the influence of the Catholics. Jobst had always been a Lutheran, but the depth of his faith was showing under pressure from the Counter-Reformation. When the time came, he scurried to Catholics, as did many of his relatives. No need to upset the archduke. Bad for trade.

  So Kepler stayed on.

  In the middle of all this, he naively found himself caught in a feud between two prodigious scientific egos. On one side was Tycho Brahe, the famous Danish nobleman turned astronomer. On the other was Nicholas Reimarus Ursus, “the Bear,” and Tycho’s predecessor as imperial mathematician. Ursus had once been a swineherd, and his manners hadn’t changed much since then. He was crude, abusive, and crafty, and his position at court was as much the result of theft as it was of accomplishment. When the Mysterium Cosmographicum came out, Kepler sent a copy to Ursus, asking his opinion. He wasn’t above a little flattery, and heaped it on, calling Ursus the greatest mathematician of the age, and so on and so forth. Ursus never wrote back, but he kept the letter tucked away and dropped it into his next book, whole and entire. That was the book in which he stole Tycho Brahe’s idea about the solar system and claimed it for his own, and then used Kepler to verify his brilliance. Tycho couldn’t stomach Copernicus’s idea of a moving earth, so he had cooked up a new system for himself, one that set all the other planets together orbiting around the sun, as Copernicus did, but then set the sun and the planets orbiting the earth, as Ptolemy did. Though it was more complex than it needed to be, it was a nice little bridge between the two systems.

  When Tycho read Ursus’s book, he was furious. Who was this Bear, this swineherd, to steal his work? And who was this Kepler to heap such praises on him? The first Kepler heard about it was in a letter from Mästlin. Kepler had sent two copies of Mysterium Cosmographicum along with a letter to Tycho at Wandsburg, and Tycho complained to Kepler by letter, protesting the theft and Kepler’s part in it. That letter never arrived, but Tycho had sent a copy of his letter to Mästlin, and Mästlin sent a frantic letter off to Kepler, which did get through in late November 1598. Mästlin warned Kepler that he had made a fool of himself, that he had made a terrible mistake, and that his career was on the line.15 Mästlin said that Kepler should never have praised Ursus and reminded him that he had once told Kepler that the man’s work was trash. Kepler didn’t understand a thing, because he had never received Tycho’s original letter, so he asked Mästlin to send a copy of the letter he had received from Tycho.

  When the letter arrived, it wasn’t as bad as Mästlin had made out.16 Tycho had a few doubts about Kepler’s polyhedral theory, but he found it ingenious and asked Kepler to try it on the Tychonic system, as he had done on the Copernican. Then he remarked that Copernicus’s measurements of the planetary distances were not accurate enough to prove Kepler’s theory, and that Kepler might find Tycho’s measurements more serviceable. Then in a long postscript he complained to Kepler about his letter of praise to Ursus. He had no doubt that Kepler never realized that Ursus would include his letter in that “defamatory and criminal publication,” and he hoped that Kepler would supply Tycho with a short statement of the facts that would help Tycho in a court action he was planning against Ursus. The letter was velvet and iron, praise and complaint, and seemed to be an act of kindness. Still, Mästlin had informed Kepler that Tycho had written to him in a separate letter, complaining much more directly about Kepler’s praise and criticizing the Mysterium Cosmographicum much more sharply.

  Kepler was quite chagrined, for he did not want to burn any bridges with Tycho, a great man who looked kindly on his work, and so he wrote back at once, apologizing and defending himself, explaining that he had only meant to praise Ursus in a general way and had no idea that the Bear would publish his letter, implying that Kepler was a party to the scheme. “That nobody that I was then searched for a famous man who would praise my new discovery. I begged him for a gift and, behold, and it was he who extorted a gift from the beggar.”17 Tycho was eventually mollified, but it took more than a few letters to do so. The incident jarred Kepler from his näiveté and forced him to enter the politics of the age.

  As it turned out, Kepler certainly needed Tycho more than he needed Ursus to keep his own work going. What Tycho had said in his letter was correct. Tycho had the observations that he needed. While cooling his heels in Graz, Kepler decided to push on with his astronomical studies and realized from Tycho’s letters that Copernicus’s astronomical data was not accurate enough. Kepler could see that his regular solids did not quite fit the data and that he would need Tycho’s more accurate observations to verify the Mysterium Cosmographicum. But Tycho kept his observations to himself and would not pass them around, so Kepler would need to wheedle them out of him. Writing to Mästlin on February 26, 1599, Kepler said: “This is my opinion of Tycho Brahe: He has riches in abundance, which he does not quite use the way most talented people do. One has to take pains, therefore, which I did for my part, with all appropriate modesty, to wrest those riches from him, to beg him to disclose all of his observations, unchanged.”18

  The next few years would draw the two men closer together and into a collaboration that would change Kepler’s life. After Tycho’s death, Kepler would publish the data in Tycho’s name and title them the Rudolphine Tables after Emperor Rudolf II. The one major disagreement between them, however, was over Copernicus. Tycho rejected Copernicus on theological grounds, while Kepler embraced him, also on theological grounds. Tycho believed that because humans were created in the image of God, then their little place in the universe had to be at the center. God placed them there so they could get a good view of the great cosmic show and thus come to praise and honor God even more. There was no greater theological master than the universe itself. Kepler agreed in pri
nciple, but Tycho’s system still seemed overly complex and unwieldy to him, a patchwork compromise that was unmindful of the elegance of God’s plan. God’s plan must be rational, and rational meant geometrical, and geometrical meant elegantly simple. And so, while Tycho was thinking like an astronomer, Kepler was thinking like a mathematician.

  However, there was still one worry, one tiny dark cloud, that bothered him. If Copernicus was right and the earth moved around the sun, then there should be some visible parallax, a shifting back and forth, of the stars from one season to the next, as an astronomer would first observe them from one side of the orbit and then from the other. However, no one could find any parallax. Tycho couldn’t find it and used that fact as evidence for the centrality of earth. But there were other possibilities. One was that the universe was infinite, as Nicholas of Cusa said, and then because the stars were infinitely distant, there wouldn’t be any parallax visible. Still, Kepler couldn’t accept that on general principle. The fact that the stars might not be at an infinite distance, but might be very, very far away was also possible, but Kepler had no way to prove that. Even Tycho’s fine instruments couldn’t have measured that. Such a discovery had to wait until 1838, when Friedrich Wilhelm Bessel observed the stars using instruments more refined than anything available in Kepler’s day.

  So Kepler went on to other problems. Why was the period of the moon’s motion apparently longer in winter than in summer? Kepler explained that by mechanical forces, his vis motoria of the sun, coupled with another vis motoria of the earth itself. He also asked why there was a reddish color to the moon during lunar eclipses. This led him to raise questions of optics, which became important to him later. Finally, he burrowed into the question of chronology, trying to pinpoint biblical events through astronomical means. Herwart von Hohenburg involved him in trying to find the year of the Roman civil war between Caesar and Pompey, which Kepler placed at 51 B.C.