The purpose of this volume on mission and unity is to bring to public attention a broad overview of the history, development, and perspectives of the role of mission in the pursuit of unity and the central biblical focus on unity as a prerequisite for an authentic witness in mission. The volume raises concrete questions: If the churches can agree on unity for mission, then does this visible unity go any further than the "mutuality, partnership, collaboration, and networking" of the Edinburgh 2010 Common Call? Does the call to unity or communion imply common touchstones, structures, or ministries to serve the communion of churches in mission?