Swift wrote that Gulliver’s Travels was based upon “a great foundation of Misanthropy,” and the least attractive qualities of the human race furnish the most pervasive theme of the book. This theme intensifies until it finds its most extreme expression in the Yahoos at the end of the book. Gulliver’s description of the first Yahoos he encounters is consistent with their looking like humans, but he does not himself see the resemblance until his Houyhnhnm master places him side by side with a Yahoo. He accepts the Houyhnhnms’ view of the world completely, regarding them as the wisest beings he has ever met. He therefore finds himself agreeing with their assessment of humanity as being identical to the Yahoos in all important respects, and perhaps even worse, since humans have a greater capacity for destruction. Gulliver comes to detest humans so completely that by the conclusion of the book, he cannot bear to be near one, even his wife and children.

The Houyhnhnms’ perception of the Yahoos is foreshadowed in part 2 by the king of Brobdingnag, who enquires into the laws and customs of England in much the same way as Gulliver’s Houyhnhnm master. The king is described by Gulliver as the wisest and most admirable character in the first half of the book, and he shares the Houyhnhnms’ horror of war, disdainfully refusing when Gulliver offers to share the secret of gunpowder with him. The way in which human folly and evil are presented therefore alternates between the four parts of the story. In parts 1 and 3, the vices of humanity are satirized directly in the self-importance, deviousness, cruelty, and violence of the Lilliputians, then in the prodigality, impracticality, and foolish conformity of the scholars on Laputa and in Lagado. In parts 2 and 4, the king of Brobdingnag and Gulliver’s Houyhnhnm master provide the commentary on the specific vices of the English described to them by Gulliver.

The catalogue of human failings Swift presents is very long indeed. One of his favorite techniques is to make a long list of pejorative words to drive home the sheer variety of folly and evil against which he is inveighing. The king of Brobdingnag provides an example when he describes the history of England which Gulliver has related to him as “a heap of conspiracies, rebellions, murders, massacres, revolutions, banishments, the very worst effects that avarice, faction, hypocrisy, perfidiousness, cruelty, rage, madness, hatred, envy, lust, malice, and ambition, could produce.” Another technique which creates some of Swift’s most memorable effects is to give a detailed historical account of the ludicrous origins of some quarrel, like the dispute in Lilliput over the correct end at which to crack an egg.