Insider movements literally turn the world of traditional Christian mission efforts upside down. Must one leave their original religious affiliation in order to follow Jesus Christ? This question has been controversially debated in mission theology for years. The book analyzes the debate surrounding insider movements in the Islamic context and critically examines the missiological roots and theological assumptions of an emerging insider missiology. Finally, the findings are discussed in relation to theological boundary cases and their performances of scripture, space, and confession. This book is intended for anyone who wants to engage in depth with one of the largest mission theological debates of recent decades.