In 1766 philosopher, novelist, composer, and political provocateur Jean-Jacques Rousseau was a fugitive, decried by his enemies as a dangerous madman. Meanwhile David Hume--now recognized as the foremost philosopher in the English language--was being universally lauded as a paragon of decency. And so Rousseau came to England with his beloved dog, Sultan, and willingly took refuge with his more respected counterpart. But within months, the exile...