Resonances and Repercussions of Kepler’s Harmony of the World

In 1619 the Harmonices mundi libri V was published, which Kepler considered his greatest work. It is well-known and famous for containing the Third Law of Planetary Motion, but book IV deals with his attempt to reform astrology within a Pythagorean-Platonic framework, and here he presented a new understanding of the mechanism of the aspects. Kepler’s “astrology of resonance” had repercussions among contemporary astrologers in the 17th century, such as Christopher Heydon, Abdias Trew and Peter Crüger. His ideas of a physical basis for celestial motions and were viewed critically however, and in the perspective of the Age of Enlightenment Kepler’s speculative approaches, as well as his metaphysical and religious arguments met with skepticism and disapproval. The tide turned in the Romantic Era, when just these aspects came to the fore and paved the way to an edition of Kepler’s works. The German philosophers F. W. J. Schelling (1775–1854), E. F. Apelt (1812–1859) and the astronomer J. W. A. Pfaff (1774–1835) played a crucial role in the rediscovery and reappraisal of Kepler. Pfaff worked on a German translation of the Harmonices mundi, and the teacher of mathematics Christian Frisch (1807–1881), who had studied under Pfaff in Erlangen, published the first critical edition of Kepler’s works from 1858 to 1871.