  Recall that for Du Châtelet, these first principles include epistemological principles—the principles of contradiction and sufficient reason (IP §4 and §8). Du Châtelet writes that “a hypothesis… [must] not be in contradiction with the principle of sufficient reason, nor with any principles that are the foundation of our knowledge” (IP §61). But, presumably, the principles constraining the sorts of hypotheses the scientist can posit also include metaphysical principles which can be derived directly from foundational principles of knowledge. For Du Châtelet, as shown above, these include the three-tier metaphysical account she develops, the nature of matter, and so forth.