In the Principia philosophiae, published for the first time in Latin in 1644, Descartes sets out in a synthetic form what the analyzes of the Meditations and the Discourse had brought to light, namely the articulation between the general principles of human knowledge, the principles of the sciences and his discoveries on the structure of the physical world. It is in the Letter-preface to its French translator, Abbe Picot, that the famous conception of philosophy as an arborescence also appears, starting from metaphysical roots, into a trunk of physics then three main branches which constitute medicine, mechanics and morality. Extending the metaphor, Descartes aims at the last degree of wisdom as the ultimate fruit of this organic growth of knowledge: Now as it is not from the roots, nor from the trunk of trees, that we gather the fruits, but only from the ends of their branches, so the main usefulness of philosophy depends on those of its parts which we can only learn the last .