A seafaring doctor recounts a series of fantastical voyages to strange lands that satirize human follies and institutions: he encounters tiny people with petty politics, lives among giants that expose human pettiness, visits islands of eccentric scientists and philosophers, and finally meets a society of rational horses who contrast civilized reason with the brutish, depraved creatures called Yahoos. Through increasingly dark encounters, his narrative skewers contemporary politics, pride, scientific pretensions, and human vanity while questioning the limits of reason and empathy.