Barkley introduces his subject by presenting the basic similarities between the Churches and their worship which rests upon the Christian doctrine of God, and is centred in the person and work of Jesus Christ. He differentiates Protestant doctrine from Catholic and Reformed doctrine from Protestant, whilst maintaining the universal theme that Christian worship is not simply the experience of the individual, but of the individual in community: the worship of a family, the Church.
Once these fundamentals have been established he continues with a critical analysis of the Eucharistic, Baptismal and Confirmation rites in the Scottish, English, Welsh and Irish liturgies. He differentiates between the Catholic, Evangelical and Reformed doctrines, reminding the reader of their similarities, and the doctrines in which they diversify, before he establishes the similarities between Catholic. In this sense the author claims that to be Reformed, or Presbyterian, it is essential to be Christian, Catholic and Calvinist not only in doctrine but also in worship.