Fromondus versus Galileo on Comets

Abstract

This contribution shows how Aristotelian authors used Aristotelian principles they deemed more fundamental to deny Aristotelian tenets they regarded as secondary. This general point is illustrated by taking as a case study the early seventeenth-century debate on comets. In particular, the discussion focuses on the role played in this debate by the Flemish academician Libertus Fromondus (1587–1653), professor of philosophy and theology at Leuven, and very actively engaged in debating the ‘new’ science with many natural philosophers around Europe, including Descartes and Galileo. Fromondus criticises the Aristotelian account of comets but rejects Galileo’s explanation as well. Fromondus uses some entrenched Aristotelian principles against the Aristotelian conclusion that comets are terrestrial exhalations. For Fromondus, as it was for Tycho Brahe, superlunary comets would count against the solid spheres and for fluid planetary heavens. However, not everyone took the route followed by Fromondus. One might even count Galileo among the traditionalists, or at least among Tycho’s opponents, about comets. The upshot is that Fromondus made significant modifications to his Aristotelianism to accommodate astronomical novelties such as superlunary comets. While he could be thought of as a traditionalist, spending his whole career as an academic, he made changes that went well beyond what could be described as the articulation of the Aristotelian tradition.