The Astronomer and the Witch: Johannes Kepler's Fight for his Mother

  • Ulinka Rublack
Oxford University Press: 2015. 9780198736776 | ISBN: 978-0-1987-3677-6

On the cover of The Astronomer and the Witch is a portrait of Johannes Kepler: confident, well dressed, half-smiling. This is the image that the imperial mathematician projected to his peers and patrons. But it is not the Kepler whom we meet in Ulinka Rublack's enthralling book — anxious, harassed by financial and family problems, and not even the main character. Rublack's protagonist is the great astronomer's mother, the unfairly accused “witch” of the title. In placing Katharina centre stage, Rublack tells a new story, one that is as much social history as it is scientific revolution.

Katharina Kepler depicted here being threatened with torture. Credit: SPL

As women in early modern Europe aged and their fertility declined, so did their status. In a small town such as Leonberg in the duchy of Württemberg, part of present-day Germany, even a respectable property owner like Katharina Kepler could not escape the stigma of age. Yet women did not all face this challenge equally. Rublack juxtaposes Katharina's hard life with the luxurious retirement of Sibylle, widowed duchess of Württemberg, on whom, in a way, her fate came to depend.

While Katharina struggled to work her land and raise children, often without their father, the rough ground behind Leonberg Castle was cleared to provide Sibylle with spectacular gardens. Investing in medicinal plants added to the duchess's standing as a patroness of the poor and sick. Katharina, tired and short-tempered, did not enjoy the same indulgence. Her use of herbal remedies, common enough at the time, raised suspicion after a local woman blamed her illness on a “witches' brew” served by Katharina. After more allegations, and many delays, in 1619 Katharina was formally accused of witchcraft.

What distinguishes Katharina's case from thousands like it is the involvement of her famous son — the reason that the trial records have been preserved. Sifting through these, Rublack reconstructs an atmosphere of anxiety and suspicion as Württemberg slid into the Thirty Years' War. Accusations of witchcraft threw whole families under suspicion, and the taint of religious unorthodoxy could damage careers, as Johannes Kepler discovered when his Calvinist leanings blocked him from a post at the University of Tübingen. As Rublack notes, to win patronage required “not only a powerful intellect and vision, but also books, ink, piety, and perfect manners”. Having mastered these resources in his precarious career as mathematician to three emperors, Kepler now deployed them on behalf of his family. After all, he had achieved fame promoting a controversial position, Copernicanism, for which standards of proof were considerably higher than those required to burn a witch.

Rublack shows how Kepler bent his experience towards deconstructing faulty arguments and marshalling evidence for Katharina's defence. The legal system provided checks and balances, for example by requiring multiple witnesses, but in practice short cuts were taken. The case against Katharina was assembled by administrators sympathetic to her accusers, and witnesses gave conflicting evidence or described events from their childhoods. To this might be added, at any time, a 'confession' under torture. Convicted witches were usually burned alive.

In this fraught environment, Kepler repeatedly revised his Harmony of the World (1619): a five-part magnum opus that included his third law of planetary motion and his views on topics as diverse as musical theory and astrology. In a chapter on psychology, Kepler betrayed his own ambiguous feelings on his mother's plight, asking whether she had brought her misfortune on herself. Yet, by the time he prepared her final defence two years later, the astronomer had devised a new narrative: one that granted old women such as Katharina a role as knowledge-makers.

Rublack argues that Kepler justified his mother's medical practice by drawing a parallel with privileged women such as Sibylle. He claimed that women's experience and observation, gained (often painfully) over long periods of time, “constituted a basis for reputable and probable, if not certain knowledge”. Kepler defended his mother by using Sibylle as an unimpeachable role model of a pious woman dispensing medical care.

Kepler wins the day, for although Katharina spoke in her own defence, it is her son's arguments that are preserved verbatim in the trial documents, commenting on and judging women's behaviour. Chained in her cell at the centre of the controversy, Katharina's own voice is harder to hear. Rublack calls out Kepler's past biographers for dismissing his mother as quarrelsome, difficult, “witch-like”. If I have one criticism of the book, it is that its title plays to that stereotype, rather than to the nuanced characterization that the author has drawn. Rublack's vigorous, early modern anti-heroine was, surely, entitled to her anger.