The Marquis de Condorcet, a mathematician and one of the more radical of his group, described his fellow philosophes as “a class of men less concerned with discovering truth than with propagating it.” That was the spirit which animated the great Encyclopédie, the most ambitious publishing enterprise of the century. It appeared in 17 volumes between 1751 and 1765, after checks and delays that would have disheartened anyone less committed than its publisher, André-François le Breton, or its chief editor and presiding genius, Denis Diderot. Its publishing history is rich in incident and in what it reveals of the ambience of the Enlightenment. The critical point was reached in 1759, when French defeats made the authorities sensitive to anything that implied criticism of the regime. The publication of Helvétius’ De l’esprit, together with doubts about the orthodoxy of another contributor, the Abbé de Prades, and concern about the growth of Freemasonry, convinced government ministers that they faced a plot to subvert authority. If they had been as united as the officials of the church, the Encyclopédie would have been throttled. It was placed on the Index of Forbidden Books, and a ban of excommunication was pronounced on any who should read it; but even Rome was equivocal. The knowledge that Pope Benedict XIV was privately sympathetic lessened the impact of the ban; Malesherbes, from 1750 to 1763 director of the Librairie, whose sanction was required for publication, eased the passage of volumes he was supposed to censor. Production continued, but without Rousseau, an early contributor, who became increasingly hostile to the encyclopaedists and their utilitarian philosophy.

Diderot’s coeditor, the mathematician Jean le Rond d’Alembert, had, in his preface, presented history as the record of progress through learning. The title page proclaimed the authors’ intention to outline the present state of knowledge about the sciences, arts, and crafts. Among its contributors were craftsmen who provided the details for the technical articles. Pervading all was Diderot’s moral theme: through knowledge “our children, better instructed than we, may at the same time become more virtuous and happy.” Such utilitarianism, closely related to Locke’s environmentalism, was one aspect of what d’Alembert called “the philosophic spirit.” If it had been only that, it would have been as useful as Ephraim Chambers’ Cyclopaedia (1727), which it set out to emulate. Instead, it became the textbook for the thoughtful—predominantly officeholders, professionals, the bourgeoisie, and particularly the young, who might appreciate Diderot’s idea of the Encyclopédie as the means by which to change the common way of thinking. In the cause, Diderot sustained imprisonment in the jail at Vincennes (1749) and had to endure the condemnation and burning of one of his books, Philosophic Thoughts (1746). There was nothing narrow about his secular mission. Pensées sur l’interprétation de la nature (1753) advanced the idea of nature as a creative process of which man was an integral part. But his greatest achievement was the Encyclopédie. Most of the important thinkers of the time contributed to it. Differences were to be expected, but there was enough unanimity in principles to endow the new gospel of scientific empiricism with the authority that Scripture was losing. It was also to provide a unique source for reformers. Catherine II of Russia wrote to the German critic Friedrich Melchior Grimm for suggestions as to a system of education for young people. Meanwhile, she said she would “flip through the Encyclopédie; I shall certainly find in it everything I should and should not do.”