Brian Strayer, a historian at Andrews University, offers here a wealth of interesting information about a major movement in seventeenth- and eighteenth-century French Catholicism, specifically about many very devout and some fanatical people.

Jansenism was a rigoristic and puritanical school of thought named for Cornelius Jansen (1585–1638), a professor of theology at Louvain. The book is practically encyclopedic in its coverage of leading Jansenists, such as Abbé de Saint-Cyran, Antoine Arnauld, Blaise Pascal, and the nuns of the great convent of Port-Royal. All these were tireless in pursuing their cause against many adversaries, especially the Jesuits—whom they perceived as lax in their moral teachings—several popes who censured Jansenist doctrines, and Kings Louis XIV and Louis XV.

In the 1730s some Jansenists became involved with accounts of miracles at the grave of a very austere man named Francois de Pâris at the church of Saint-Médard in a poor area in Paris. Somehow fervor here, and then in other places, became steadily more intense and led people to more extravagant acts, convulsions, wild dances, and finally gruesome tortures of each other. Jansenists were deeply divided in their judgments on the convulsionnaries, and Strayer notes correctly that Saint-Cyran and Arnauld would certainly not have approved. This book presents an extraordinary array of precise data on the successive phases of Jansenism, the people, and their writings and struggles, including numerous charts and tables, with profusely clear citations of sources. Very scholarly, it is also a great read.