The nature of the Church

“The whole meaning of this present age between Christ's coming and His coming again is that in it the powers of the age to come are at work now to draw all men into one in Christ. When the Church ceases to be one, or ceases to be missionary, it contradicts its own nature.” (Lesslie Newbigin: Missionary Theologian p126) [emphasis mine]

Newbigin, as clearly as anyone I have read, makes the unity of the church and its missionary nature essential to its identity. The very doctrine that defines its mission is that which defines its unity: the atonement worked on the cross. Thus, "when the Church ceases to be one, or ceases to be missionary, it contradicts its own nature."