The church is a distinct community of people of every type and all ages, and from every race, ethnic group, nation and social category, who confess that Jesus of Nazareth, the Messiah, is the Son of God and the only saviour of all humanity. They confirm their belief that this Jesus has called them individually and together into a fellowship of his followers, with the purpose of exhibiting the qualities of a life transformed by the power of God’s Spirit, under the rule of God’s new order (the kingdom), and of bringing others into the sphere of God’s saving actions. The church, though an organization separate from any other, is not detached from the world. It exists in the world. Hence the direction of its mission is not into the world from outside, but rather from one part of the world to another. However, as we shall see, God calls it to be separate from the world in the sense of not accepting beliefs or joining in activities that are at variance with God’s blueprint for human wellbeing.
J. Andrew Kirk in The Church and the World (Christian Doctrine in Historical Perspective)