Theo is an untrustworthy narrator. Because the book was written, not only from his point of view, but also from someone who is initially seemingly innocent, we are supposed to feel that we can trust him. But as the book continued on, we see how that was never the case.
Theo initially presents himself as rational and trustworthy, but as his motives unraveland the reader is forced to question whether he’s helping Alicia or manipulating her. This shift causes the reader to doubt their own judgment, evoking the experience of alienation.
Gulliver travels to strange lands and eventually develops a deep respect for the Houyhnhnms, advocating for the extermination of all humans (only to discover that he is a human and will therefore have to leave); when he returns home, he is disgusted by his wife and children.