Gulliver tries to travel to Luggnagg, but he finds no ship available. Since he has to wait a month, he is advised to take a trip to Glubbdubdrib, the island of magicians. Gulliver visits the governor of Glubbdubdrib, and he finds that servants who appear and disappear like spirits attend the governor. The governor tells Gulliver that he has the power to call up any shade he would like. Gulliver chooses Alexander the Great, who assures him that he died not from poison but from excessive drinking. He then sees the Carthaginian general Hannibal and the Roman leaders Caesar, Pompey, and Brutus.
Gulliver sets apart one day to speak with the most venerated people in history, starting with Homer and Aristotle. He asks the French philosophers René Descartes and Pierre Gassendi to describe their systems to Aristotle, who freely acknowledges his own mistakes while pointing out that systems of nature will always vary from age to age.
Gulliver then returns to Luggnagg, where he is confined despite his desire to return to England. He is ordered to appear at the king’s court and is given lodging and an allowance. He learns that subjects are expected to lick the floor as they approach the king, and that the king sometimes gets rid of opponents in the court by coating the floor with poison.
The Luggnaggians tell Gulliver about certain immortal people, children born with a red spot on their foreheads who are called Struldbrugs. Gulliver devises a whole system of what he would do if he were immortal, starting with the acquisition of riches and knowledge. Contrary to his fantasy, however, he is told that after the age of thirty, most Struldbrugs grow sad and dejected, and by eighty, they are incapable of affection and envious of those who are able to die. If two of the Struldbrugs marry, the marriage is dissolved when one reaches eighty, because “those who are condemned without any fault of their own to a perpetual continuance in the world should not have their misery doubled by the load of a wife.” He meets some of these people and finds them to be unhappy and unpleasant, and he regrets ever wishing for their state.
Gulliver is finally able to depart from Luggnagg, after refusing employment there, and he arrives safely in Japan. From there he gains passage on a Dutch ship by pretending to be from Holland and sets sail from Amsterdam to England, where he finds his family in good health.
Swift continues his mockery of academia by describing the projects carried out in the cities below Laputa. The academy serves to create entirely useless projects while the people starve outside its walls. Each project described, such as the extraction of sunbeams from a cucumber, is not only impossibly flawed but also purposeless. Even if its scientific foundations were correct, it would still serve no real purpose for the people meant to gain from it. The result is a society in which science is promoted for no real reason and time is wasted as a matter of course.