  Du Châtelet's starting point—her first chapter of the Foundations—is also a consideration of first principles, but she starts immediately with first principles of knowledge, and hers are very different from Descartes'. Indeed, her first principles are distinctively Leibnizian and Wolffian, and number exactly two; they are the principle of contradiction (hereafter PC) and the principle of sufficient reason (hereafter PSR). In what follows, we present some general ideas that are helpful to bear in mind when thinking about Du Châtelet's use of the PC and PSR. We then draw some important conclusions regarding these principles as they are found in Wolff, noting points on which Wolff departs from Leibniz with regard to first principles of knowledge. And finally, we turn to a consideration of how Du Châtelet employs these principles in her work.