Girolamo Cardano’s Meteorological Predictions: Hippocratism, Weather Signs, Winds, and the Limits of Astrology

Abstract The subject of meteorology was central to Girolamo Cardano’s thought. It held together his encyclopedism by tying the celestial realm to the sublunary world and human action. Meteorology, for Cardano, links abstract knowledge to the practical and operative. While many of his Aristotelian predecessors understood weather prediction as distinct from meteorology as a natural philosophical field, Cardano’s profound interest in conjectural arts and probabilistic reasoning led him to tie causal explanations to methods of forecasting future conditions of the air and their effects on humans, especially regarding health and disease. While it might be expected that Cardano would have emphasized astrological tools for weather forecasting, instead he went in a different direction, namely, embracing the ancient tradition of weather signs and revising Aristotelian theories of winds. At the end of his career, which he mostly spent writing commentaries on Hippocratic writings, he integrated his understanding of weather signs with Hippocratic rules of prognosis, revising traditional understandings of the causes of winds.