Protogaea, an ambitious account of terrestrial history, was central to the development of the earth sciences in the 18th century and provides key philosophical insights into the unity of Gottfried Wilhelm Leibniz’s thought and writings. In the book, Leibniz offers observations about the formation of the earth, the actions of fire and water, the genesis of rocks and minerals, the origins of salts and springs, the formation of fossils, and their identification as the remains of living organisms. Protogaea also includes a series of engraved plates depicting the remains of animals—in particular the famous reconstruction of a “fossil unicorn”—together with a cross section of the cave in which some fossil objects were discovered. Though the works of Leibniz have been widely translated, Protogaea has languished in its original Latin for centuries. Now Claudine Cohen and Andre Wakefield offer the first English translation of this central text in natural philosophy and natural history. Written between 1691 and 1693, and first published after Leibniz’s death in 1749, Protogaea reemerges in this bilingual edition with an introduction that carefully situates the work within its historical context.