Even the most ardent devotee of ecclesiastical history cannot realistically claim for his special interest a major role in Clio's fraternity in this age of high secularization. Yet it may be said, I believe, that the role is growing rather than diminishing for historians generally as they assess the value of scientific and professional works such as those of the Fliche and Martin series, The Christian Centuries edited by Louis J. Rogier, Roger Aubert, and David Knowles, the successive volumes of Concilium. Theology in The Age of Renewal devoted to ecclesiastical history, and the projected Oxford History of the Christian Church under the guiding hand of Owen Chadwick. And parenthetically at the outset I should like to make it clear that while most of the materials used in this paper are related to the Roman Catholic Church simply because of my greater familiarity with her story, I use the term ‘Christian Church’ in the broadest possible sense to embrace the Protestant, Anglican, and Orthodox communions, as well as that of the Church to which I owe my personal faith and allegiance.