His fourth voyage is go to the land of the Houyhnhnms, who are horses endowed with reason. Their rational, clean, and simple society is contrasted with the filthiness and brutality of the Yahoos, beasts in human shape. Gulliver reluctantly comes to recognize their human vices. Gulliver stays with the Houyhnhnms for several years, becoming completely enamored with them to the point that he never wants to leave. When he is told that the time has come for him to leave the island, Gulliver faints from grief. Upon returning to England, Gulliver feels disgusted about other humans, including his own family.