Jesus prayed that the disciples would be one so that the world will believe . This is the glorious end of the union of believers, that the world will be led to the Christ. An ecumenicity that is an end in itself can only produce a vacuous institutional union, a super-church of some sort. Oneness of faith does not call for a conformity to a single super-church or an identity to some rigid doctrinal pattern. Congregations may well remain diverse, whether cultural or doctrinal, and still be one together in the Lord, accepting and loving each other as fellow heirs of the promises.
Mariners watch the polar star for guidance to the goal in view.
Stone saw that unity of believers is the road by which we reach the heart of an unbelieving world. A divided church contradicts the very message of love it proclaims. But when the world sees that believers love each other even when they do not agree, it is impressed. Jesus assures us that men will be convinced that we are disciples when they see our love for one another. This is our polar star.