An Unlikely Encounter: Arabic Astrology, Seismology, and Vulcanology at the Dawn of the Enlightenment

The seventeenth century was an intense period of study of volcanoes and earthquakes. Major European thinkers such as Johannes Kepler, Athanasius Kircher, and René Descartes all had something to say about the causes of volcanic eruptions and earthquakes. While none of their theories proved completely right, the fact that an astronomer, a Jesuit polymath, and a philosopher contributed to the debate is indicative of its significance for seventeenth-century intellectuals. While different physical and causal explanations about the formation of lava and the quaking of the earth were proposed, one is often dismissed by historians of geology, namely astrological-astronomical causation. This paper will examine a series of works written by Italian and French authors around the time of the 1631 eruption of Vesuvius and soon after the 1703 earthquake in central and southern Italy to illustrate how, in this period, the Arabic theory of great conjunctions and the study of eclipses, were taken into serious consideration by a number of intellectuals as a possible cause of these earthly phenomena. Despite the alleged demise of astrology in the seventeenth century, this paper will argue that astro-meteorology remained a well respected and convincing scientific discipline, and that the Arabic authors who underpinned this discipline remained frequently quoted authorities in this field.