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Introduction to the Encyclopédie

Title page

In the exhibit, MIT’s copy of the first volume of text of the folio edition was opened to its frontispiece and title page. The association of four Parisian publishers responsible for printing the work, listed near the bottom of the title page, delivered the unbound sheets of the first volume in 1751. Subscribers were initially charged 280 livres, but over the years, as the work expanded in size, the cost rose to a total of 980 livres, and by the end of the 1770s, copies of this first folio edition of text and plates sold for 1200 to 1500 livres. (A livre was equal to one day’s wages for a manual laborer in eighteenth-century France.) MIT’s copy of the first folio edition entered its collection in 1951, when the Institute shrewdly purchased the 17 volumes of text, 11 volumes of plates, and 5 supplemental volumes for five dollars per volume!


The frontispiece to the Encyclopédie is an allegorical composition in which female figures representing Reason and Philosophy unveil the figure of Truth, positioned in the upper center of the composition. A radiant light emanates from her, while to the left Imagination prepares to adorn her with a garland of flowers. Other allegorical figures representing the arts, sciences and trades look on or display instruments or texts specific to their fields. Interestingly, the frontispiece was not designed and engraved until 1772, well after the publication of the seventeen text volumes had concluded in 1765 and Diderot had turned his attention to the plates.

Tree of Knowledge

The “System of Human Understanding,” often referred to as the “Tree of Knowledge,” also appeared in the first volume of the work. At the end of the seventeenth century, the Englishman John Locke had argued that the human mind at birth was a blank slate; he thought that we came to understand ourselves and the world around us via the intake of sensory perceptions which the mind then organized into rational categories. Based on this sensationalist psychology, Diderot and d’Alembert argued in the “Preliminary Discourse” to the Encyclopédie that human knowledge consisted of three branches:

  • Memory, expressed as natural, civil, and sacred history
  • Reason, divided into knowledge of man and knowledge of nature
  • Imagination (allegorized in the frontispiece next to Truth), which took the form of sacred and profane poetry

These three aspects of human understanding literally form the “branches” of the Encyclopédie’s Tree of Knowledge. In this conceptualization, note how theology becomes a subset of philosophy, grouped with divination and black magic. “Heretical” assumptions such as these made devout Catholics and Protestants alike hostile to the Encyclopedists and their work.

See English translations: