Diderot, d'Alembert and the Launch of the Encyclopédie

The Encyclopédie began as a modest business plan: the Paris publisher André Le Breton wanted a French translation of Ephraim Chambers's English Cyclopaedia of 1728. Under the editors Denis Diderot, a writer who had been jailed at Vincennes in 1749 for an irreligious essay, and Jean le Rond d'Alembert, a celebrated mathematician, the project grew into something far more ambitious. Its first volume appeared in 1751, promising a 'reasoned dictionary of the sciences, arts and trades'.

The aim was to gather all useful knowledge, arrange it rationally and, as Diderot wrote, 'change the common way of thinking'. Contributors included Voltaire, Rousseau, Montesquieu and many lesser-known specialists. Because the work was sold by subscription to thousands of buyers, it was also a major commercial enterprise. It became the defining project of the French Enlightenment, both a reference book and a vehicle for criticism of superstition, intolerance and arbitrary power.