 The truths that Descartes takes to be “most useful to us” do not consist of discoveries original to his philosophy. Rather, they reflect a general outlook on the world that could be embraced by someone without Cartesian sympathies: the existence of an omnipotent and supremely perfect God; the immortality of the soul; the vastness of the universe; that we have duties to a larger whole of which we are a part; that our passions often distort the goodness of their objects. What Descartes can claim at most (and what he does claim in the preface to the Principles of Philosophy) is that he has supplied better reasons for believing these propositions to be true; he has established certain knowledge where before there was only unstable belief.