The French monk and historian Jean Mabillon (1632-1707) made an important contribution to the science of historical investigation by discovering a way of dating ancient manuscripts.

Jean Mabillon was born on Nov. 23, 1632, the son of a peasant who lived close to Reims. He was a capable student and a religiously devout young man. After spending a year in the diocesan seminary, he became a novice in 1653 in the Benedictine monastery in Reims. He was ordained a priest in 1660, and his quiet scholarly competence prompted his abbot to send him to the abbey of St-Germain-des-Prés in Paris in 1664 to take part in the work of historical research in which the monks there were engaged.

The abbey belonged to a group of reformed Benedictine monasteries called the Congregation of St. Maur. The Maurists were beginning to establish a reputation in Paris for sound historical scholarship. Mabillon's first major...