Swift's Gulliver's Travels is arguably the most famous literature to emerge from this 18th-century Tory satirical tradition. It is the loudest, funniest, and yet in some ways most desperate cry to stop the trends set in motion by seventeenth-century philosophy. In Book IV we discover how Gulliver's journey to discover what man is becomes a journey into madness. Here we find ourselves faced with a cruel attack on man. This is an attack that uses two of the most striking literary metaphors for man: the Houyhnhnms and the Yahoos. The former are beings similar to horses in all respects, except for the possession of absolute reason; the latter are creatures that have an extraordinary resemblance to man except for their animalistic brutality.