Denis Diderot, a key figure in the advancement of Enlightenment philosophy, envisioned the project of the Encyclopedie with his collaborator Jean D’Alembert. The prospectus was accompanied by a diagram of the “Map of Human Knowledge” which Diderot described as "the Genealogical Tree of All the Arts and Sciences." The Systême figuré groups all learning under memory (history), reason (philosophy) or imagination (poetry). God, as the source of knowledge, is conspicuously absent.