Abstract
In this chapter, I examine similarities and divergences between Du Châtelet and Descartes on their endorsement of the use of hypotheses in science, using the work of Condillac to locate them in his scheme of systematizers. I conclude that, while Du Châtelet is still clearly a natural philosopher, as opposed to modern scientist, her conception of hypotheses is considerably more modern than is Descartes’, a difference that finds its roots in their divergence on the nature of first principles.