In Jonathan Swift’s Gulliver’s Travels, the rational horses are called Houyhnhnms. They appear in Part IV, where Lemuel Gulliver reaches a remote land ruled by intelligent, articulate horses. Their name imitates the sound of a horse’s neighing and is pronounced in several slightly different ways.
The Houyhnhnms live in an orderly society governed by reason, calm judgment, and strict social rules. Swift contrasts them with the Yahoos, brutish humanoid creatures who resemble humans and embody greed, violence, vanity, and disorder. Gulliver admires the horses so intensely that he begins to regard ordinary human beings as repulsive Yahoos.
The episode is more complicated than a simple celebration of reason. The Houyhnhnms’ rational society can also appear cold and inhumane: they show little sympathy, regulate family life, and discuss the treatment of Yahoos in unsettlingly practical terms. Swift therefore uses the contrast to satirize both human corruption and the dangers of reason without compassion.
Brobdingnagians and Lilliputians belong to earlier voyages, while Yahoos are the Houyhnhnms’ human-like counterparts.