Three Main Themes From Swift's "Gulliver's Travels"
The Finite Nature of Knowledge
One theme in Gulliver's Travels is the notion that there is a limit on what people are supposed to know. This theme receives the most exposure in Swift's portrayal of the island of Laputa (Spanish for a woman of ill repute). The people who live there have one eye pointing inward and one eye pointing straight upward, showing introspection and aspiration -- but also resulting in real-world blindness. The academy of Balnibarbi serves to ridicule the pursuit of knowledge without useful outcomes -- one such example involves the attempts to pull sunbeams from cucumbers.
In Brobdingnag and the land of the Houyhnhnms, reason is the governing virtue, but it is not accompanied by the pursuit of knowledge. The focus is finding a way to live calmly, wisely and consistently. Note that the king of Brobdingnag, for example, is not an expert about politics -- in fact, he knows just about nothing. However, his country is not suffering as a result. The Houyhnhnms can tell you the length of a month based on their lunar observations, but constellations would leave them speechless. They know, in other words, what they need to know.
The Individual and the Community
Several of the societies that Gulliver visits show different structures than the traditional Western family model. The Houyhnhnms give each couple two horses, one male and one female. If a couple has two females, then they swap one with a couple that has bred two males. The Lilliputians raise their children in a common setting instead of in family units.
Despite all of these different models, two truths emerge: there is no perfect social structure, and there is always tension between the individual's needs and the goals of the community. The Lilliputians are even sillier than the British and French were in their territorial disputes before and during the time when Swift was alive, and the Houyhnhnms come across as robotic. They are so closely assimilated that they don't appear to have any sort of autonomy.
Lemuel Gulliver is not the voice of Jonathan Swift, although both men lived at odds with their communities. Swift was an Anglo-Irish priest who also wrote vigorous political satire, railing against the cruelties of the British crown; Lemuel Gulliver is a doctor who continually takes positions as a ship's doctor, leaving his family behind, because he cannot meld with society. However, Gulliver's lack of comfort comes from a lack of identity. He is happiest with the Houyhnhnms, because he doesn't have to be anyone in particular -- he just has to follow the rules.
The ideal path, for Swift, is a medium path between the needs of the individual and the goals of the community. An individual willing to sacrifice for the greater good will mesh well with a society willing to give that individual a reasonable degree of autonomy and opportunity.
Power or Ethics?
Should a society allow the most powerful to make the rules, or should it govern itself according to ethical principles? According to Swift's "A Modest Proposal," the British government used its power rather than ethics to create its rules. The rich profited while the poor starved; the powerful accumulated more and more, while the weak were left with nothing.
In Lilliput, Gulliver has unlimited power but places himself in the service of the monarch; he drags the navy of rival Blefuscu out to sea. However, when he urinates in the queen's chamber to put out a palace fire, he is accused of treason -- a sign of how contrary to human nature it can seem to subjugate power to ethics at times.
The Laputans might be the closest analog to the relationship between England and Ireland, in Swift's opinion -- to squelch rebellion on the lower land of Balnibarbi, Laputa would threaten to hover right over the land, blocking sun and rain, or even crushing buildings and people on the land below.
Leaders who claim the high moral ground also have a hard time proving their claims. Look at the egg dispute between Lilliput and Blefuscu -- this centers on a matter of religious interpretation that has driven the nations apart.
And so what is the answer? It's easier to prove superiority based on power, but it's also easier to justify overthrowing that sort of power. On the other hand, it's harder to prove ethical superiority, but it's harder to justify rebelling against it. Small wonder, then, that so many monarchs in the age of Swift tried to rely on both.