Is the world becoming one civilization? If so, will its religions merge? Or if Christianity has a unique authority, what are the presuppositions and content of the revelation that it embodies? And how must its institutions change so that it may fulfill its mission to the nations? These are the questions asked, and to a surprising extent answered, by Lesslie Newbigin, one time Bishop of the Church of South India who lead the `missionary` studies sponsored by the World Council of Churches. All who are interested in the comparison of religions or the mission of the Church will value his presentation of vast and important themes. One of the thinkers criticized is Dr. Arnold Toynbee, who writes: `A fine book . . . I particularly admire how Bishop Newbigin states the case of people with whom he disagrees.` Another, Sir S. Radhakrishnan, writes: `I have read it through with great interest. It is written with deep conviction and expresses the orthodox Christian point of view.`