Abbot Butler is well known as a Catholic scholar, one of whose concerns has always been the theology of the Church. At the time of the Second Vatican Council, whose over-riding intention is the promotion of Christian Unity, his book is appropriate. It is concerned with what may be considered the crux of the matter, not the papacy, but the unity of the Church as a society. The Abbot quotes frequently from the works of Anglican scholars, and conducts his closely argued thesis quietly with many references to the Biblical and historical data.