 Book IV of "Gulliver's Travels" is the keystone, in some ways, of the entire work, and critics have traditionally answered the question whether Gulliver is insane (and thus just another victim of Swift's satire) by questioning whether or not the Houyhnhnms are truly admirable.Gulliver loves the land and is obedient to a race that is not like his own.The Houyhnhnm society is based upon reason, and only upon reason, and therefore the horses practice eugenics based on their analyses of benefit and cost.