A Voyage to the Country of the Houyhnhnms by Jonathan Swift

Gulliver sets out as captain of a ship, but after the mutiny of his crew and a long confinement in his cabin, he arrives in an unknown land. This land is populated by Houyhnhnms, rational-thinking horses who rule, and by Yahoos, brutish humanlike creatures who serve the Houyhnhnms. Gulliver sets about learning their language, and when he can speak he narrates his voyages to them and explains the constitution of England. He is treated with great courtesy and kindness by the horses and is enlightened by his many conversations with them and by his exposure to their noble culture.