“Voltaire” was the pen name of François-Marie Arouet (1694–1778), a playwright, poet, essayist, and widely read popularizer of Sir Isaac Newton. His Philosophical Letters (1734) and Philosophical Dictionary (1764) both express his brilliant wit and underlying sense of social justice. He made great fun of Gottfried Leibniz (1646–1716) as Dr. Pangloss in the satire Candide, but although he thought that this was not the best of all possible worlds, as Pangloss did, he believed improvement was possible on specific issues.

Voltaire’s empiricism was similar to that of John Locke (1632–1704) in that he was a moderate skeptic who also thought that human knowledge is generally adequate for the lives most people lead. In other words, we know what we need to know. He argued for toleration and objected to the narrowness of church Christianity. By the same token, he did not go as far as Jean-Jacques Rousseau (1712–1778) in extolling simplicity over civilization. He replied to Rousseau after he gave him a copy of The Social Contract: “I have received your new book against the human race, and thank you for it. Never was such a cleverness used in the design of making us all stupid. One longs, in reading your book, to walk on all fours. But as I have lost that habit for more than sixty years, I feel unhappily the impossibility of resuming it.”