In a word, Madame, I can assure you that while writing
this work, I had posterity before my eyes at every line. --
d'Alembert to Madame du Deffand, December 22, 1752.

Of all the shorter works of the eighteenth-centuryphilo-
sophes, the Preliminary Discourse to Diderot's Encyclopedia is
incomparably the best introduction to the French Enlighten-
ment. ^intro.1 It is the Enlightenment insofar as one can make such a
claim for any single work; with a notable economy and vigor
it expresses the hopes, the dogmas, the assumptions, and the
prejudices we have come to associate with the movement of
the philosophes. From the moment of its publication in
1751, many leaders of the Enlightenment recognized it as a
masterful statement of their "philosophy," and even the men
who were fearful of its implications acclaimed it for its lucid-
ity and compactness. No less a judge than the great Montes-
quieu complimented d'Alembert on his work in the most
flattering terms: "You have given me great pleasure. I have
read and reread your Preliminary Discourse. It has strength,
it has charm, it has precision; richer in thoughts than in
words, likewise rich in sentiment -- and my praises might go
on." ^intro.2 Frederick the Great ranked it above his grandest mili-

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