D’Alembert praised the 16-year-old’s gifts, taught him and became a close friend. The youngest of Diderot’s Encyclopaedists, he was a regular at d’Holbach’s salon, and wrote a biography of another good friend, Voltaire. He encouraged Monge to submit his research to the Académie des Sciences, and Legendre to write what became a classic geometry textbook. He was one of the first mathematicians Lagrange met when he came to Paris, and helped liberalise Franklin’s views on slavery and racial equality. He posthumously edited out pious references to God in his correspondent Euler’s published letters.