The sixteenth and seventeenth centuries marks a period of transition between the vitalistic ontology that had dominated Renaissance natural philosophy and the Early Modern mechanistic paradigm endorsed by, among others, the Cartesians and Newtonians. This paper will focus on how the tensions between vitalism and mechanism played themselves out in the context of sixteenth and seventeenth century chemistry and chemical philosophy, particularly in the works of Paracelsus, Jan Baptista Van Helmont, Robert Fludd, and Robert Boyle. Rather than argue that these (...) natural philosophers each embraced either fully vitalistic or fully mechanistic ontologies, I hope to demonstrate that these thinkers adhered to complicated and nuanced ontologies that cannot be described in either purely vitalistic or purely mechanistic terms. A central feature of my argument is the claim that a corpuscularian theory of matter does not entail a strictly mechanistic and reductionistic account of chemical properties. I also argue that what marks the shift from pre-modern vitalistic chemical philosophy to the modern chemical philosophy that marked the Chemical Revolution is not the victory of mechanism and reductionism in chemistry but, rather, the shift to a physicalistic and naturalistic account of chemical properties and vital spirits. (shrink)