From The Telegraph:
‘How I love the English boldness!,” Voltaire said. “How I love those who say what they think!” Superficially, this was a light-hearted remark, in a letter to a friend, about the literary daring of Swift’s Tale of a Tub. “It is a treasure house of jokes,” he said, “of which the rest of the world has no idea. Pascal only makes jokes at the expense of the Jesuits, but Swift entertains and instructs us at the expense of the whole human race.” But of course, it was not just a light-hearted remark: if Voltaire loved English boldness, it was because at home, in 18th-century France, he could not say what he thought; and that, in a sense, was what the French Enlightenment was really all about.
If in England and Scotland it was about science or philosophy or economics, in France the central political issue was freedom of speech. French intellectuals such as Diderot, Rousseau, Maupertuis and Montesquieu were of course exploring new worlds of ideas, but they were much less free to say or write what they liked than were Newton or Locke or Adam Smith across the Channel. “It is impossible,” said Voltaire in mid-century, “for a writer who thinks freely, not to be persecuted in France.” He himself had already twice been imprisoned in the Bastille and he spent his life in conflict with the repressive authorities of the ancien régime. He was first imprisoned, in his early twenties, for writing verses that were recklessly critical of the Regent, Philippe, Duke of Orléans. There was no trial and no conviction; yet he spent a year in the cells, entirely at the Duke’s pleasure.
Nine years later, in 1726, he was again thrown without trial into the Bastille, this time for quarrelling in public with an offensive young nobleman; but he so feared another long and indefinite sentence in the dungeons that he immediately volunteered to go into exile in England instead; the authorities, short-sightedly, accepted his offer.
More here.