Explaining Astrological Influence with Cartesian Natural Philosophy: Peter Megerlin’s Manuscript Astrologia Cartesiana (ASHB1530, circa 1680)

Abstract Action at a distance was one of the key features of astrology. Once a thriving discipline, astrology in the early modern period entered a crisis that ultimately culminated in its marginalization from the domain of scholarly recognition. Critics of astrology took issue, among other things, with the causative process of the supposed astrological action at a distance – traditionally based on the light shed by celestial bodies – denying that light could be a conduit of astrological influence. In response to such criticisms, some astrologers attempted to explain astrological influence based on different theoretical and natural-philosophical foundations, as, for instance, by employing Cartesianism. This paper focuses on the so far-unpublished manuscript Laurenziana ASHB 1530, Astrologia Cartesiana , by the German astronomer, mathematician and astrologer Peter Megerlin (1623–1686), a professor in Basel. It shows Megerlin’s eclectic use of Cartesian elements in his treatment of the natural-philosophical bases of astrology, paying particular attention to his attempt to explain astrological influence on corpuscularian grounds. It also contributes to the reconstruction of Megerlin’s biographical and scholarly profile, focusing on the significance of his engagement with Copernican cosmology and astrology in seventeenth-century Basel.