Gulliver's Travels has been the recipient of several designations: from Menippean satire to a children's story, from proto-science fiction to a forerunner of the modern novel.
Published seven years after Daniel Defoe's wildly successful Robinson Crusoe, Gulliver's Travels may be read as a systematic rebuttal of Defoe's optimistic account of human capability. In The Unthinkable Swift: The Spontaneous Philosophy of a Church of England Man, Warren Montag argues that Swift was concerned to refute the notion that the individual precedes society, as Defoe's novel seems to suggest. Swift regarded such thought as a dangerous endorsement of Thomas Hobbes' radical political philosophy and for this reason Gulliver repeatedly encounters established societies rather than desolate islands. The captain who invites Gulliver to serve as a surgeon aboard his ship on the disastrous third voyage is named Robinson.
Scholar Allan Bloom points out that Swift's critique of science (the experiments of Laputa) is the first such questioning by a modern liberal democrat of the effects and cost on a society which embraces and celebrates policies pursuing scientific progress.
A possible reason for the book's classic status is that it can be seen as many things to many different people. Broadly, the book has three themes:
- A satirical view of the state of European government, and of petty differences between religions
- An inquiry into whether men are inherently corrupt or whether they become corrupted
- A restatement of the older "ancients versus moderns" controversy previously addressed by Swift in The Battle of the Books
In storytelling and construction the parts follow a pattern:
- The causes of Gulliver's misadventures become more malignant as time goes on—he is first shipwrecked, then abandoned, then attacked by strangers, then attacked by his own crew.
- Gulliver's attitude hardens as the book progresses—he is genuinely surprised by the viciousness and politicking of the Lilliputians but finds the behaviour of the Yahoos in the fourth part reflective of the behaviour of people.
- Each part is the reverse of the preceding part—Gulliver is big/small/wise/ignorant, the countries are complex/simple/scientific/natural, and the forms of government are worse/better/worse/better than England's.
- Gulliver's viewpoint between parts is mirrored by that of his antagonists in the contrasting part—Gulliver sees the tiny Lilliputians as being vicious and unscrupulous, and then the king of Brobdingnag sees Europe in exactly the same light; Gulliver sees the Laputians as unreasonable, and his Houyhnhnm master sees humanity as equally so.
- No form of government is ideal—the simplistic Brobdingnagians enjoy public executions and have streets infested with beggars, the honest and upright Houyhnhnms who have no word for lying are happy to suppress the true nature of Gulliver as a Yahoo and are equally unconcerned about his reaction to being expelled.
- Specific individuals may be good even where the race is bad—Gulliver finds a friend in each of his travels and, despite Gulliver's rejection and horror toward all Yahoos, is treated very well by the Portuguese captain, Don Pedro, who returns him to England at the novel's end.
Of equal interest is the character of Gulliver himself—he progresses from a cheery optimist at the start of the first part to the pompous misanthrope of the book's conclusion and we may well have to filter our understanding of the work if we are to believe the final misanthrope wrote the whole work. In this sense Gulliver's Travels is a very modern and complex novel. There are subtle shifts throughout the book, such as when Gulliver begins to see all humans, not just those in Houyhnhnm-land, as Yahoos. However, a feminist perspective of Gulliver's Travels argues that it is misogyny, and not misanthropy, that is shown in Gulliver.
Throughout, Gulliver is presented as being gullible; he believes what he is told, never perceives deeper meanings, is an honest man, and expects others to be honest. This makes for fun and irony; what Gulliver says can be trusted to be accurate, and he does not always understand the meaning of what he perceives.
Also, although Gulliver is presented as a commonplace "everyman", lacking higher education, he possesses a remarkable natural gift for language. He quickly becomes fluent in the native tongue of any strange land in which he finds himself, a literary device that adds verisimilitude and humour to Swift's work.
Despite the depth and subtlety of the book, it is often classified as a children's story because of the popularity of the Lilliput section (frequently bowdlerised) as a book for children. One can still buy books entitled Gulliver's Travels which contain only parts of the Lilliput voyage.
A well-known underlying theme in Gulliver's Travels is misogyny. Swift uses satire to openly mock misogyny throughout the book, with one of the most cited examples of this coming from Gulliver's description of a Brobdingnagian woman:
"I must confess no Object ever disgusted me so much as the Sight of her monstrous Breast, which I cannot tell what to compare with, so as to give the curious Reader an Idea of its Bulk, Shape, and Colour.... This made me reflect upon the fair Skins of our English Ladies, who appear so beautiful to us, only because they are of our own Size, and their Defects not to be seen but through a magnifying glass...."
This open critic towards aspects of the female body is something that Swift often brings up in other works of his, particularly in poems such as The Lady's Dressing Room and A Beautiful Young Nymph Going To Bed.
A well known criticism of Swift's misogyny by Felicity A. Nussbaum proposes the idea that “Gulliver himself is a gendered object of satire, and his antifeminist sentiments may be among those mocked.” Gulliver’s own masculinity is often mocked, seen in how he is made to be a coward among the Brobdingnag people, repressed by the people of Lilliput, and viewed as an inferior Yahoo among the Houyhnhnms.
Another criticism of Swift's use of misogyny delves into Gulliver's repeated use of the word 'nauseous,' and the way that Gulliver is fighting his emasculation by commenting on how he thinks the women of Brobdingnag are disgusting.
"Swift has Gulliver frequently invoke the sensory (as opposed to reflective) word "nauseous" to describe this and other magnified images in Brobdingnag not only to reveal the neurotic depths of Gulliver's misogyny, but also to show how male nausea can be used as a pathetic countermeasure against the perceived threat of female consumption. Swift has Gulliver associate these magnified acts of female consumption with the act of "throwing-up" — the opposite of and antidote to the act of gastronomic consumption."
This commentary of Deborah Needleman Armintor relies upon the way that the giant women do with Gulliver as they please, in much the same way as one might play with a toy, and get it to do everything one can think of. Armintor's comparison focuses on the pocket microscopes that were popular in Swift's time. She talks about how this instrument of science was transitioned to something toy-like and accessible, so it shifted into something that women favored, and thus men lose interest. This is similar to the progression of Gulliver's time in Brobdingnag, from man of science to women's plaything.
Misanthropy is a theme that scholars have identified in Gulliver's Travels. Arthur Case, R.S. Crane, and Edward Stone discuss Gulliver's development of misanthropy and come to the consensus that this theme ought to be viewed as comical rather than cynical.
In terms of Gulliver's development of misanthropy, these three scholars point to the fourth voyage. According to Case, Gulliver is at first averse to identifying with the Yahoos, but, after he deems the Houyhnhnms superior, he comes to believe that humans (including his fellow Europeans) are Yahoos due to their shortcomings. Perceiving the Houyhnhnms as perfect, Gulliver thus begins to perceive himself and the rest of humanity as imperfect. According to Crane, when Gulliver develops his misanthropic mindset, he becomes ashamed of humans and views them more in line with animals. This new perception of Gulliver's, Stone claims, comes about because the Houyhnhnms' judgement pushes Gulliver to identify with the Yahoos. Along similar lines, Crane holds that Gulliver's misanthropy is developed in part when he talks to the Houyhnhnms about mankind because the discussions lead him to reflect on his previously held notion of humanity. Specifically, Gulliver’s master, who is a Houyhnhnm, provides questions and commentary that contribute to Gulliver’s reflectiveness and subsequent development of misanthropy. However, Case points out that Gulliver's dwindling opinion of humans may be blown out of proportion due to the fact that he is no longer able to see the good qualities that humans are capable of possessing. Gulliver’s new view of humanity, then, creates his repulsive attitude towards his fellow humans after leaving Houyhnhnmland. But in Stone's view, Gulliver’s actions and attitude upon his return can be interpreted as misanthropy that is exaggerated for comic effect rather than for a cynical effect. Stone further suggests that Gulliver goes mentally mad and believes that this is what leads Gulliver to exaggerate the shortcomings of humankind. Over time, though, Gulliver is able to get used to humanity again.
Another aspect that Crane attributes to Gulliver’s development of misanthropy is that when in Houyhnhnmland, it is the animal-like beings (the Houyhnhnms) who exhibit reason and the human-like beings (the Yahoos) who seem devoid of reason; Crane argues that it is this switch from Gulliver’s perceived norm that leads the way for him to question his view of humanity. As a result, Gulliver begins to identify humans as a type of Yahoo. To this point, Crane brings up the fact that a traditional definition of man – Homo est animal rationale (Humans are rational animals) – was prominent in academia around Swift’s time. Furthermore, Crane argues that Swift had to study this type of logic (see Porphyrian Tree) in college, so it is highly likely that he intentionally inverted this logic by placing the typically given example of irrational beings – horses – in the place of humans and vice versa.
Stone points out that Gulliver's Travels takes a cue from the genre of the travel book, which was popular during Swift's time period. From reading travel books, Swift’s contemporaries were accustomed to beast-like figures of foreign places; thus, Stone holds that the creation of the Yahoos was not out of the ordinary for the time period. From this playing off of familiar genre expectations, Stone deduces that the parallels that Swift draws between the Yahoos and humans is meant to be humorous rather than cynical. Even though Gulliver sees Yahoos and humans as if they are one and the same, Stone argues that Swift did not intend for readers to take on Gulliver’s view; Stone states that the Yahoos’ behaviors and characteristics that set them apart from humans further supports the notion that Gulliver's identification with Yahoos is not meant to be taken to heart. Thus, Stone sees Gulliver’s perceived superiority of the Houyhnhnms and subsequent misanthropy as features that Swift used to employ the satirical and humorous elements characteristic of the Beast Fables of travel books that were popular with his contemporaries; as Swift did, these Beast Fables placed animals above humans in terms of morals and reason, but they were not meant to be taken literally.
Pedro de Mendez is the name of the Portuguese captain who rescues Gulliver in Book IV. When Gulliver is forced to leave the Island of the Houyhnhnms, his plan is "to discover some small Island uninhabited" where he can live in solitude. Instead, he is picked up by Don Pedro's crew. Despite Gulliver's appearance—he is dressed in skins and speaks like a horse—Don Pedro treats him compassionately and returns him to Lisbon.
Though Don Pedro appears only briefly, he has become an important figure in the debate between so-called soft school and hard school readers of Gulliver's Travels. Some critics contend that Gulliver is a target of Swift's satire and that Don Pedro represents an ideal of human kindness and generosity. Gulliver believes humans are similar to Yahoos in the sense that they make "no other use of reason, than to improve and multiply...vices"  Captain Pedro provides a contrast to Gulliver's reasoning, proving humans are able to reason, be kind, and most of all: civilized. Gulliver sees the bleak fallenness at the center of human nature, and Don Pedro is merely a minor character who, in Gulliver's words, is "an Animal which had some little Portion of Reason."