Gerhard Groot, Or Gerard The Great, founder of the congregation of "Brethren and Clerks of the Common Life," born in Deventer, Holland, in 1340, died Aug. 20, 1384. He studied in Paris, graduated master of arts at the age of 18, and taught philosophy and theology at Cologne, where his eloquence and learning gained him the surname of Magnus. Although not in priestly orders, he hold several rich benefices, besides a considerable patrimony, and lived in great luxury until an interview with the prior of a Carthusian monastery at Geldern induced him to enter the religious state. He renounced his benefices, and after three years was ordained deacon, refusing higher advancement. He now passed through the principal cities of the diocese of Utrecht, preaching with extraordinary effect to immense audiences, and working reforms no less among the clergy than among the laity. He assailed scholastic theology, taught that the reading of the Scriptures and of the writings of the fathers should be one of the chief occupations of a Christian, and translated the Psalms and the church office into Dutch. Having collected some of the best manuscript copies of the Bible and the fathers, he established in his own house at Deventer a society whose principal employment was the transcribing of these books.

He gave them a rule of life, prescribed community of goods, and placed over them Florent Radewyn, professor in the university of Prague, a rich man who had been converted by Gerhard's preaching. The " Brethren and Clerks of the Common Life," as the associates were called, became immensely popular. In a short time they counted 100 communities, among which there were some of women. They encountered great opposition from the mendicant orders, who sought to identify them with the Beguins, and also from the "Brethren of the Free Spirit;" but Gerhard defended himself with great skill, and obtained the formal sanction of Gregory XI. in 1376. During a visit to Ruysbroek he resolved to give to his order the rule of the canons regular, and shortly afterward on his deathbed recommended this change to Radewyn. The first monastery of canons regular was established in 1380 at Windesheim near Zwolle, and the order, thenceforward bearing the name of Windesheim, numbered in 1460 upward of 150 monasteries. The corrected text of the Bible published at Windesheim, from collated manuscripts of the version of St. Jerome, was approved by the popes and used as a chief authority in the edition of Sixtus V. The school of Deventer belonging to this order produced Thomas a Kempis, the reputed author of the "Imitation of Christ."