The intellectual domain of Gottfried Wilhelm von Leibniz cannot be captured in a single word. For most of his life, he was a jurist, a courtier, a diplomat, and a librarian; he also made huge contributions to the study of logic, geometry, physics, botany, physiology, linguistics, and of course, the infinitesimal calculus. And yet, many of his ideas remain obscure to the modern reader. What in the world is a Monad? Why does Leibniz care so much about the so-called Principle of Sufficient Reason? And how could he claim that this is the Best of all Possible Worlds? John and Ken discuss the most important philosopher you know the least about with Daniel Garber from Princeton University, author of Leibniz: Body, Substance, Monad.