As the church moves towards its 21st century of existence, it is confronted by challenges it has never known before. Globalization, the rise of different socio-political orders and a growing tendency towards a post-modern understanding of the world are but some of the issues. This changing world demands self-reflection from the church. It has to consider its place, identity and function, thereby giving rise to the exploration of its mission.In this book, the ecclesiology of Karl Barth is explored. By considering Barth’s understanding of the church’s relationship with different parties such as God, other religions, those outside the Christian faith, the State and its own inner dynamics, the church will be reminded of its missionary function in the world. The church’s relationships are important for they direct the way in which it fits into the world. When it considers that it exists purely because of God’s self-revelation, and that its own existence is an act of faith in response to this divine self-disclosure, it becomes aware of defined parameters within which the church can operate under the banner of mission.