The purpose of this volume on mission and unity is to bring to public attention a broad overview on the history, development and perspectives on 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 touch stones, structures or ministries to serve the communion of churches in mission? Might the Holy Spirit be prompting a fresh mission to the churches to promote unity?