Two courses of lectures dedicated to Leibniz were given by Gilles Deleuze at the University of Paris VIII (Vincennes) in 1980 and 1986-1987 and became the last lecture courses in the life of the philosopher. Under the cover of the book are printouts of tape recordings that preserve the lively intonation and emotional structure of Deleuze’s speech. Unlike the book he later wrote, “The Fold: Leibniz and the Baroque,” the lectures reveal a much more comprehensive picture of the German thinker’s work. Particular attention is paid to the analysis of the connection between Leibniz's mathematical discoveries and his philosophy, parallels between Leibniz, Spinoza, Descartes, Kant and Whitehead, as well as the main concepts of Leibniz metaphysics. Leibniz's philosophy becomes in Deleuze not only the key to understanding the Baroque era, but also the most important tool for constructing a modern picture of the world.