The Brethren of the Common Life (Latin: Fratres Vitae Communis) was a Roman Catholic pietist religious community founded in the 14th century by Gerard Groote, formerly a successful and worldly educator who had had a religious experience and preached a life of simple devotion to Jesus Christ. Without taking up irrevocable vows, the Brethren banded together in communities, giving up their worldly goods to live chaste and strictly regulated lives in common houses, devoting every waking hour to attending divine service, reading and preaching of sermons, labouring productively and taking meals in common that were accompanied by the reading aloud of Scripture: "judged from the ascetic discipline and intention of this life, it had few features which distinguished it from life in a monastery", observes Hans Baron.
 The Brethren and the Devotio Moderna
The Brethren's confraternity is the best known fruits of the Devotio Moderna, the Modern Devotion. A small band of followers attached themselves to Groote and became his fellow-workers, thus becoming the first "Brethren of the Common Life" (Dutch: Broeders des gemeenen levens). The reformer was opposed by the clergy, whose lax lives he denounced in his preaching as decadent and evil, but his zeal for purifying the Catholic faith and the morality of its followers won many to his cause. The best of the secular clergy even enrolled themselves in his brotherhood, which in due course was approved by the Pope. Groote, however, did not live long enough to finish the work he had begun. He died in 1384, and was succeeded by Florens Radewyns, who two years later refounded the famous monastery of Augustinian canons at Windesheim, near Zwolle, which was thenceforth the centre of the new association.
 Education and activity
The Confraternity of the Common Life were in many ways similar to the Beghard and Beguine communities which had flourished two centuries earlier but were by then declining. Its members took no vows, neither asked nor received alms; their first aim was to cultivate the interior life, and they worked for their daily bread. Books and the library were central to the communities of Brethren, whose scrupulous copies of works of piety supported their houses and put the texts in which they found spiritual sustenance in many hands. The houses of the brothers and sisters occupied themselves with literature and education, and their priests also with preaching. When Groote began, education in the Netherlands was still rare, contrary to the situation in Italy and the southern parts of the Holy Roman Empire of the German Nation; the University of Leme of the schools of Liège was only a vague memory. Apart from some of the clergy who had studied at the universities and cathedral schools in Paris or in Cologne, there were few scholars in the land; even amongst the higher clergy there were many who were ignorant of the scientific study of Latin, and the ordinary burgher of the Dutch cities was quite content if, when his children left school, they were able to read and write the Medieval Low German and Diets.
Groote determined to change all this. The Brethren worked consistently in the scriptorium; afterwards, with the printing press, they were able to publish their spiritual writings widely. Amongst them are to be found the best works of 15th century Flemish prose. The Brethren spared no pains to obtain good masters, if necessary from foreign countries, for their schools, which became centres of spiritual and intellectual life of the Catholic Church; amongst those whom they trained or who were associated with them were men like Thomas à Kempis, Dierick Maertens, Gabriel Biel, Jan Standonck (1454 - 1504), priest and reformer, Master of the Collège de Montaigu in Paris, and the Dutch Pope Adrian VI.
Martin Luther studied under the Brethren of the Common Life at Magdeburg before going on to the University of Erfurt. Another famous member of the Brethren of the Common Life was Desiderius Erasmus of Rotterdam. His mystical and scholarly efforts produced many works of literature. One of his greatest contributions to the Christian faith was a critical Greek New Testament (1514) which challenged the previous New Testament text translations (specifically the Vulgate). Commonly called Erasmus, he embraced ecclesiastical structure yet challenged the Augustinian view (people do not choose God, but God is the only one who brings people into grace and salvation), the nature of the human will, and the corruption and problems of the late medieval church.
Before the fifteenth century closed, the Brethren of the Common Life had placed in all Germany and the Netherlands schools in which teaching was offered "for the love of God alone."
Gradually the course of study, at first elementary, embraced the humanities, philosophy, and theology. The religious orders were not impressed, as the Brethren were neither monks nor friars, but they were protected by Popes Eugene IV, Pius II, and Sixtus IV. Cardinal Nicholas of Cusa had been their pupil and so became their stanch protector and benefactor. He was also the patron of Rudolph Agricola (Rudolf de Boer), who in his youth at Zwolle had studied under Thomas à Kempis; and through this connection the Brethren of the Common Life, through Cusa and Agricola, influenced Erasmus and other adepts in the New Learning. More than half of the crowded schools ' in 1500, Deventer had over two thousand students ' were swept away in the religious troubles of the sixteenth century. Others languished until the French Revolution, while the rise of universities, the creation of diocesan seminaries, and the competition of new teaching orders gradually extinguished the schools that regarded Deventer and Windesheim as their parent establishments.
The community of the Brethren in Herford went over bodily to the Reformation, But despite of it, the local council threatened to close their house. The Brethren wrote to Martin Luther 1532, who defended their community life by writing to the council of the city. To Jacob Montanus and Gerhard Wilskamp he wrote in the end of January 1532: "Your way of life, since you teach and live according to the Gospel, pleases me no end". If only "there had been, and today there were more convents like yours!...Abide by your way of life and use it to spread the Gospel (as you do)!" The house of the Brethren of the Common Life in Herford remained in existence as a Lutheran brotherhood until 1841.