How we can see Part 4 of a Gulliver's as satire?
It is clearer after Gulliver's rescue that the reason why part 4 is a satire becomes clear. Given the contrast between the Yahoos and the Houyhnhms, it can be inferred that Swift was intending to make some kind of statement, but once Gulliver returns home and his loathing of humans mimics his loathing of the Yahoos we start to see that the Yahoos were obviously meant to stand in for humans. In this case the contrast between the nasty and brutish Yahoos and the entirely reasonable Houyhnhms makes it clear that Swift is satirizing humans in their penchant for using the advantages and abilities they have only to multiply their vices.
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