Gulliver justifies his grim portrait of humankind to the reader, explaining that his time among the Houyhnhnms had opened his eyes to the evils of human nature and human society and that he had in fact been hoping to live permanently among the Houyhnhnms and never return to England.
Gulliver acknowledges outright the shift in his perspective that has only been implied earlier: he feels the Houyhnhnms have helped him see the dark “truth” about human society and made him realize he wants nothing to do with humans.
The master horse, having reflected on Gulliver’s portrait of humankind, concludes that the European Yahoos are “animals, to whose share…some small pittance of reason had fallen” of which they made no use than “to aggravate…natural corruptions and…acquire new ones.” Thus, they were in many ways worse off than the reason-less Yahoos, for they also lacked those Yahoos’ physical strength, swiftness, agility, and strong claws. As to the European state, the master horse points out that they are “plainly owing to our gross defects in reason, and by consequence in virtue; because reason alone is sufficient to govern a rational creature.”
From Gulliver’s accounts, the master horse deduces the “truth” about human society that so alters Gulliver’s perspective. According to this view, humans are completely lacking in moral power, are pathetically disabled physically, and have managed to organize a society that is simply the grotesque reflection of their unreasonable minds.
The master horse continues, saying that, apart from their physical inferiority, the European Yahoos Gulliver has described resemble the Yahoos of the Houyhnhnms in countless other respects. The Yahoos of the Houyhnhnms also loathe the sight of one another’s bodies (which the master horse assumes is the real reason for Europeans’ clothes); greedily hoard food; overeat; purge; suffer sickness from immoderation (which is cured by eating their own excrement); seek intoxication; live in filth; suck up to their leaders, then throw their excrement at that leader as soon as he is replaced; lust after and hoard jewels; suffer malaise when indolent (which can only be cured by physical exertion); and indulge the grotesque lust of their females.
Though, from the Europe’s perspective, European clothes, access to fancy foods/luxury goods, wealth, political savvy, and complex emotions indicate their society’s refinement and civility, the master horse’s Houyhnhmn perspective sees the same qualities as evidence of the opposite. He recognizes those qualities as evidence of savagery and brutality, linking the possessors of those qualities to the Yahoos and indicating their society’s degradation.