 In addition to Descartes’ method of doubt, Poulain also adopts his scientific method and his discussion of the order of the sciences, as it is presented in the preface to the French translation of Principia philosophiae (see also Pellegrin 2013; Reuter 2017: 34–37). Descartes famously compares the whole of philosophy, which is here understood as including all different forms of knowledge, to a tree, where the 