The author shows that the New Testament pattern of unity is two-fold. It is a pattern of complementarity, not of uniformity. One emphasises the institutional, traditional and particular: the other the persona, dynamic and universal. Yet the two are one. What is the nature of Christian unity? Is it Sacramental, Organic, Federal, Spiritual. These are questions that demand careful examination when the different Christian traditions are drawing closer to one another in a common desire to heal the divisions which hinder the witness of the Church to the world. In any attempt to deal with these questions full weight must be given to the evidence of the New Testament itself. What kind of unity does it reveal? The author sees a two-fold pattern of unity in the New Testament. One strand in its witness to Christ, to the Apostles, and to the Church emphasises the institutional, traditional and particular; the other the persona, dynamic and universal. Yet the two strands are actually one. Their unity is more comprehensive, more creative, than any undifferentiated unity could be. To establish this thesis and to suggest some of its implications is the purpose of Leuba’s stimulating book.