Swift's Theory of Humanity Jonathan Swift used part IV of Gulliver's Travels to present his theory that reason is the essence of mankind. To present his theory, Swift places humans (Yahoos) and horses (Houyhnhnms) on a secluded island. The humans forfeited the ability to use reason, and the horses received the ability to use reason. Swift will use the horses to show how reason can change a simple animal into a complex, almost human species. He will use the humans to show how lack of reason can turn a complex species into a simple and irrational species. There is very little known about the private life of Jonathan Swift . He was born in the city of Dublin, Ireland on November 30, 1667. His father had died while his mother was pregnant with Jonathan. Right after the young Swift was born, his mother left him with his uncle to care for him. Jonathan was not a great student, but he went to Trinity Collage and graduated as a favor to his Uncle. Before Swift completed his masters degree, he left to join the Glorious Revolution. (Barron's) Swift's first experience in politics was in the Glorious Revolution of England. The object of the revolution was to force James II to relinquish the throne. James had worked to increase the power of the Roman Catholic Church in England. This had terrible effects on the Anglican Church. The methods in which James ruled were discriminatory against Anglicans. James fled to France, when William of Orange arrived with an army. After James had fled, Jonathan Swift became secretary to the prominent Whig, Sir William Temple. Because Swift believed that Roman Catholics had no part in English government and the Whigs objected to this idea, Swift changed parties and became a Tory. He would remain a Tory for the rest of his life. (Barron's) The main character of Gulliver's Travels is Lemur Gulliver. Gulliver makes four voyages and in each voyage he either is shipwrecked, abandoned, or banished from his ship.