An emblematic work of the Enlightenment, the Encyclopedia appeared between 1751 and 1772. It knew many hazards and had to face censorship. Inspired by Ephraim Chambers' Cyclopaedia or Universal Dictionary of Arts and Sciences, published in London in 1728, the Encyclopedia was masterfully edited by Denis Diderot and written with the help of 200 well-known collaborators. (scholars, philosophers and specialists of all disciplines). Among them are Voltaire, Montesquieu, Rousseau, Condillac, Daubenton, Jaucourt and Marmontel. The preliminary discourse, written by d'Alembert, is a summary of knowledge in the 18th century. Alain Ruhlmann, Associate Professor of Modern Literature, will return to this easy chapter of French cultural history