We see Gulliver lying all the time, as when he tells the Japanese Emperor that he is a Dutchman, or when he attempts to prevent the Houyhnhnms from discovering that his clothes are not part of his skin. Gulliver's ease with lying during his adventures makes his frequent claims to the reader that he is "chiefly studious of truth" (2.1.16) seem a little, well, doubtful. This ability of language to deceive other people is something that comes up a lot in this book: Gulliver tells the Master Horse that the purpose of lawyers is to confuse and distract people from the truth by using special lawyer-talk. And Gulliver finally discovers the Houyhnhnms have no word for lying – the closest they come to it is "the thing which is not" (4.5.6) – because the virtuous purpose of communication is to speak one's own thoughts. The Houyhnhnms find lying to go against reason.
Lawyers come in for particularly tough criticism from Gulliver because he believes that they will defend anything, whether they believe it or not, which makes all of their arguments deceitful.
Self-deception in Gulliver's Travels belongs particularly to national leaders: the Emperor of the Lilliputians, the Queen of Brobdingnag, and the King of Luggnagg are all vulnerable to Gulliver's flattery.