By comparing the malicious Dutchman to the relatively merciful pagan pirates, Swift begins a sustained disparagement of the Dutch. The Dutchman betrays a fellow Christian out of greed and malice; he would like to have Gulliver killed, whereas the pirate, at least, spares Gulliver's life. Swift is setting up a contrast between the Dutchman whom we meet here (and those we meet later) and the charitable Portuguese captain whom we meet at the end of Book IV. The Dutch are convenient villains for Swift. Already, in The Conduct of the Allies, he had indicted them and the Whigs for their conduct of the war. The Dutch, it is true, had been allies of England in Marlborough's land campaigns against France, but they were allies chosen by the Whigs.
The flying island has a long history in satire. Many other satirists had used it as simply a marvel, but Swift takes it out of the realm of the incredible. He converts it from a marvel to a device; it is graphic and rather believable because we are told in great detail how it operates. Swift also makes it doubly useful by showing how the Laputans use it as an instrument of political tyranny.
