Might versus Right
Throughout the novel the reader is confronted with images of brute strength in contest with what is right. Gulliver can defeat the Blefuscudian because of his immense size but there is little indication what the correct course of action might be. He defeats them simply because he is big. Later, in Brobdingnag, he is relentlessly oppressed by how huge everything is compared to him. Even insects are source of struggle and disgust.
Yet, the domination of the Houhynhnms over the Yahoos is one of moral superiority. Though the Yahoos are figures of brute strength and bestial will, it is the Houhynhnms who hold superiority due to their civilized ways and moral high ground.
Throughout the travels, there is a tension between individual will and the collective good of society. The Lilliputians operate as a unit but only in the face of a collective enemy. Gulliver stands out amid them because he is uniquely singular, being the only example of his kind that is known. He defeats their collective enemy as an individual. What is more, even though the Lilliputians seem to operate as a collective, they are torn by individual jealousies and conflicts. The individual will tears away at the fabric of the social good.
The Houyhnhnms operate collectively. In fact, they are the only characters in the novel who do not have proper names. The raise their young collectively. Gulliver operates as a singular individual who is cast away into a strange world. His grief at being forced to leave the Houyhnhnms seems to signal his desire to belong to a collective — to a cohesive society.
The Limits of Human Knowledge
Swift is obviously critical of the notion that humans are the measure of all things. Throughout the novel, Swift satirizes the idea that a profound scholarly devotion to knowledge is valuable. The Laputans are the best example. Though they are masters of all theoretical knowledge, they are an absolute failure at anything practical or meaningful. They fail at making clothes. The Balnabarbi are equally foolish. They are a race of learned philosophers who try to extract sunlight from cucumbers. In the end, it is the simple but virtuous Houyhnhnms in their world of simplicity and attention to practical daily life who emerge as not just the most successful but also the most harmonious creatures in the travels.