The present translation is based upon the original edition at the beginning of the first volume of the Encyclopedia in 1751. The original punctuation and capitalization have generally been modernized. Only minor changes in the Discourse were made by d’Alembert in the editions of his Mélanges de littérature, d’histoire et de philosophie, published in 1753, 1759, 1760, 1764, and 1770. Where these changes clarify the text, we have noted them. All notes are those of the translators, except where they are otherwise designated. The division into parts is also editorial.

The Preliminary Discourse was translated into English in 1752 under the title The Plan of the French Encyclopaedia or Universal Dictionary of Arts, Sciences, Trades and Manufactures, London. The translation, which was of little use for the present one, was intended as the beginning of an English project for pirating the entire Encyclopedia. For a moment this threat alarmed the French publishers, but the enterprise failed. There was one other project to translate the Encyclopedia, which came to naught in the same year.  [1] Thereafter, only isolated passages of the Discourse have been rendered into English in works on the Enlightenment. It has, however, been translated into German, Spanish, and Italian. It went through a number of French editions and reprintings, as a separate work and as a part of the various editions of d’Alembert’s works. The supply of the last one, edited by F. Picavet and published by A. Colin (Paris, 1894), which was reprinted a number of times in this century, has long since been exhausted.

This edition and translation was done under the auspices of the Society for Early Modern Studies of Davis, California. It is dedicated to my parents. I wish to thank Professors Merle Perkins and Arthur Child of Davis, Professors Roger Hahn and Carl Schorske of Berkeley, Professors Crane Brinton of Harvard and Arthur M. Wilson of Dartmouth for reading the manuscript and making helpful suggestions. Professor Sherman Stein, Thomas Lehrer, and Professor Jacques Proust of Montpellier provided information on certain technical points. The translation owes whatever merit it possesses to the collaboration of Professor Walter E. Rex of Berkeley, and his criticisms have been invaluable for all parts of the Introduction and notes. Mrs. Lee Barker, Mrs. Linda Hesse, and Mrs. Florence Fisher assisted in the preparation of the manuscript.