This paper proposes new ways of characterizing eighteenth-century French Cartesianism. Besides two widely-accepted elements—the belief in “strict mechanism” and the idea that to demonstrate in physics does not involve mathematics, but reference to mechanical models—I add two more, hitherto neglected, features. First, a strong emphasis on experimentalism, namely the view that experiments are crucial to natural-philosophical practice. Second, an epistemological thesis that I call “conjecturalism,” which consists in doubting that natural philosophy would attain an ultimate truth on the nature of things. To explore these facets of Cartesianism, I focus on the works of the Jesuit Noël Regnault.