Cruelty in human nature is a theme in this book. Burton quickly realizes that peaceful people will be in danger throughout the new planet, since most of human history suffers from intense violence, slavery, warfare, and destruction. The novel explores this violence as cultures spanning across earth's geography and timeline are mixed together and placed next to one another in somewhat random fashion. Through the first third of the novel, Burton and his group constantly fight off enemies who wish to either enslave them or destroy their belongings.