Owen Chadwick describes the effects of the European Revolution of 1789 to 1815 on the Papacy, and compares Catholic Church of the ancient régime to that of the early nineteenth century. The book shows how strongly the Counter-Reformation still worked in Italy during the eighteenth century; how it was the constitutional development of states, rather than the incoming of new ideas, which forced change; how traditional was the Catholic world even in the age of the Enlightenment. It shows reform at work, and the fierce pressure on the Papacy marked first in the forced suppression of the Jesuits and afterwards in the kidnapping of two successive Popes by French governments. It shows how revolution in Italy affected church structures and brought on peasant war, yet encouraged, in a radical form, some improvements of church life towards which the earlier reformers had striven. Finally, it shows the political swing of the Restoration after the fall of Napoleon, the way in which the Church was already associated with the political right, the great difficulties of restoring church life after the evolutionary years, and the persistence, half unnoticed, of the earlier reforming ideas among Catholics.

The book describes the change from the Catholic Church of the ancien regime to the Church of the early nineteenth century as it affected the institution of the Papacy and through it the Church at large.