Gulliver's Travels, written by Jonathan Swift in 1726, is a satirical novel that tells the story of Lemuel Gulliver, a ship's surgeon who, through a series of misadventures, ends up visiting four different fantastical societies. One of these societies is inhabited by a race of intelligent horses called the Houyhnhnms.
The Houyhnhnms are a highly advanced and rational species, in contrast to the degraded and irrational human-like creatures known as the Yahoos that also inhabit their world. Gulliver becomes the servant of a Houyhnhnm master, who he refers to as "my dear horse," and learns to communicate with them through their language, which consists mainly of whinnying and other horse-like noises.
The Houyhnhnms are depicted as being superior to humans in many ways. They are rational, logical, and highly moral, and they live in a society that is free from the problems of human society, such as war, corruption, and deceit. They are also physically superior, with faster reflexes and stronger bodies than humans.
Despite their superiority, the Houyhnhnms are not portrayed as perfect beings. They are shown to be somewhat lacking in emotion and imagination, and they are unable to comprehend many of the complexities of human nature. This is exemplified in their treatment of the Yahoos, whom they see as little more than beasts of burden and who are treated cruelly as a result.
Overall, the Houyhnhnms in Gulliver's Travels serve as a commentary on the nature of intelligence and morality. Swift is using them to argue that reason and rationality alone do not necessarily lead to a better society, and that the human capacity for emotion and imagination is an important part of what makes us human. He is also suggesting that the pursuit of perfection can sometimes lead to a lack of understanding and compassion for those who are different from us.