 A new starting point in systematic reflections on the origin of the earth and living beings, showing both some similarity and also major differences from atomist speculations, dates specifically from the synthesis of natural philosophy and metaphysics put forth by René Descartes (1596–1650) in his Principia philosophiae (1st ed. 1644; 2nd ed. 1647). This treatise expanded and summarized issues he had developed earlier in Le Monde (The World, or Treatise on Light), a work published only posthumously in 1664, with an improved edition appearing in 1677.