The French philosopher and author Denis Diderot was one of the leading figures of the French Enlightenment. He was, in collaboration with d'Alembert (1717-1783), the principal editor of the Encyclopédie ou dictionnaire raisonné des sciences, des arts et des métiers [Encyclopaedia or explanatory dictionary of the sciences, arts and trades]. This great collective work, published between 1751 and 1772, had among its collaborators such personages as Montesquieu (1689-1755), Voltaire (1694-1778), Robert-Jacques Turgot (1727-1781), Georges-Louis Leclerc de Buffon (1707-1788), and Jean-Jacques Rousseau. Diderot's interests ranged over many disciplinary spheres, from philosophy to mathematics and biology, from literature to aesthetics. He wrote many important works, among which should be mentioned the Philosophical Thoughts of 1746, the Letter on the blind addressed to those who can see from 1749, The Interpretation of Nature from 1753 and the Dream of d'Alembert from 1769. In 1773 he went to St. Petersburg, where he drew up for the Empress Catherine II of Russia a number of projects for reforming society and education. He died in Paris on July 31, 1784.