Answer: Gulliver learns much about alternative ways of living and comes to appreciate the ways that various peoples have improved upon the ways that he knew in England. He also appreciates what it is like to be much larger or smaller, much better or worse, much more practical or less intelligent, than others. He has seen how what is an important difference within a culture seems petty to outsiders. Overall, he sees many things more objectively and has come to despise the usual ways of humans where he lives. The horses are not really like the Houyhnhnms, so we realize Gulliver's mistake, but we sense that Gulliver is better off with a lot of time to himself to contemplate his experiences and what they mean for living well.
In many ways, Gulliver’s role as a generic human is more important than any personal opinions or abilities he may have. Fate and circumstance conspire to lead him from place to place, while he never really asserts his own desires. By minimizing the importance of Gulliver as a specific person, Swift puts the focus on the social satire itself. At the same time, Gulliver himself becomes more and more a subject of satire as the story progresses. At the beginning, he is a standard issue European adventurer; by the end, he has become a misanthrope who totally rejects human society. It is in the fourth voyage that Gulliver becomes more than simply a pair of eyes through which we see a series of unusual societies. He is, instead, a jaded adventurer who has seen human follies—particularly that of pride—at their most extreme, and as a result has descended into what looks like, and probably is, a kind of madness.