To survey the history of the Catholic Church is, in the words of Eamon Duffy, to be left with "a sense of the intractable complexity of the historical reality of the Church and its institutions." To do justice to this complexity, Philip Hughes wrote an ambitious, three-volume survey of Church history-comprehensive in scope yet accessible in detail. In Volume I: The Church and the World in Which It Was Founded, Hughes dispenses with the chronological method, instead following the organic division of West and East and the development of the Church in those respective regions. In this "politically Roman and culturally Hellenic" world, Hughes treats the West through to the conversion of Constantine in the early years of the fourth century and the East up to the death of Justinian II in the eighth century.

At the end of antiquity, as in the other stages of history, the Catholic Church has been an "all-present, unceasingly active institution." As such, its history demands to be known. A History of the Church, Volume I, is the first part of a magisterial response to that demand.