ABSTRACTJacques Rohault is often considered to be one of the most meticulous followers of Descartes. Despite this, Rohault’s natural philosophy lacks much of the metaphysical bulwark that typifies Cartesian treatises of the seventeenth century. Instead, Rohault’s work, as well as his popular weekly meetings, strongly emphasized rigorous observation and experimentation. Traditionally, this emphasis on experiment over metaphysics is seen as a pragmatic omission to avoid the perils associated with censorship and Cartesian metaphysics. However, I find that the lack of explicit (...) metaphysics has real consequences that play out in the role Rohault assigns to experimentation. To show this, I highlight several areas where he adopts a broad experimental methodology even though Descartes explicitly rejects the relevancy of experiment on metaphysical topics. I place special emphasis Rohault’s extensive experiment on the void. In short, Rohault’s experimentation was designed to prove, through experimental mea... (shrink)