What is spiritual warfare? Can a Christian be demon-possessed? Are we called to engage territorial spirits? These provocative questions stand at the heart of evangelical discussions of the demonic. Bringing his expository skill and extensive knowledge of early Christianity to bear on the contemporary understanding of the spiritual realm, Clinton Arnold develops a biblical understanding of spiritual warfare, defines the influence demons can have on believers, and sheds invaluable light on the controversial topic of territorial spirits and the extent of believers' authority over them.