Kepler on Astrology

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Kepler's Cosmological Synthesis: Astrology, Mechanism and the Soul. Patrick J. Boner (Brill, Leiden, 2013). Pp. xiv + 187. euro101. ISBN 978-90-04-24608-9.

Kepler's Astrology. Edited by Dorian Giesler Greenbaum (Special double issue of Culture and Cosmos, vol. 14, nos 1 and 2,2010). Pp. xii + 330. £20. ISSN 1368-6534.

Johannes Kepler Gesammelte Werke, XXI 2.2. Manuscripta Astrológica, Manuscripta Pneumática, edited by Friederike Boockmann and Daniel A. De Liscia (Verlag C. H. Beck, Munich, 2009). Pp. 699. euro102. ISBN 978-3-406-578700.

The fact that the hefty volume 21.2.2 of the Johannes Kepler Collected works appears so late in the project, and was certainly not envisioned when this long and authoritative series was planned in the 1930s, speaks volumes about the change in attitudes to historical astrology over the past few decades. Without accepting anything about the efficacy of the fundamental assumptions of astrology, it is possible to sympathize with the brilliant Renaissance inquirers who faced big and fundamental questions of how things worked and who desperately wanted to find, as in Tycho Brahe's motto, Suspiciendo despido, how by looking up one could understand the cosmic forces at work below. Just because we no longer accept the premises does not mean that we should dismiss the sincere and thoughtful attempts of some of the greatest minds of the so-called scientific revolution. As Robert Westman has shown in his monumental Copemican question, a strong undercurrent of astrological aspirations underlies much of Renaissance astronomy.

The thoughtful and penetrating work by Patrick Boner reveals much about what drove Kepler's vision of the world, and much of that is very foreign to the standard picture of Kepler beavering away with page after page of numbers. Boner's Kepler's cosmological synthesis is not an easy read. His Kepler seems to be wrestling with mushy ideas, very foreign to modem science, and hard to pin onto the progress of scientific understanding. "Don't sentence me to the treadmill of calculations!", Kepler cried out at one point. "Leave me time for my philosophical speculations." And at the heart of these philosophical speculations is Kepler's unorthodox astrology. Yes, if we truly want to understand Kepler's psyche, Boner's book is an essential supplement to the standard biographies.

Boner works systematically through Kepler's bibliography, paying special attention to the Cosmo graphical mystery, On the new star, On comets,Apology, and The harmony of the world. (It is difficult to find the Latin titles in the text.) He also mines the correspondence in Kepler's Gesammelte Werke. …