Effluvia,Action at a Distance,and the Challenge of the Third Causal Model

In the early modern age, two causal models are clearly identifiable: action at a distance—a typical Renaissance paradigm, widespread among thinkers involved in natural magic and seventeenth-century Neoplatonists—and action by contact, on which both the Aristotelians (including the Jesuits) and the Cartesians agreed. Pierre Gassendi too seems to endorse the motto: ‘Nihil agit in distans nisi prius agit in medium’ Nothing acts at a distance unless it acts through a medium]. In this essay, it will be shown that a third causal model exists, according to which material bodies are surrounded by ‘atmospheres’ of effluvia or qualities, which spread within a circumscribed ‘sphere of activity’, whose extension is peculiar to each body. In particular, it will be shown: (1) what the third causal model was like, from an ontological point of view, that is, how it centred on the concepts of effluvium and spiritus, or qualitas; (2) what this model was like, from a gnoseological point of view; (3) how it was theorized by three physicians—Girolamo Fracastoro, Daniel Sennert, and Sylvester Rattray; it stood on Gassendi’s qualitative corpuscularianism, and was exemplarily utilized by Robert Boyle.