Thomas Hemerken was born at Kempen in the Rhineland and sent at about twelve to Deventer, where the Brethren of the Common Life ran a house for poor scholars. The Brethren were the institutional face of the Devotio Moderna, a movement of interior reform started by Gerard Groote which held that the machinery of scholastic theology had become an obstacle, and that what mattered was the ordering of a life: reading slowly, examining oneself, working, and keeping silence.
He absorbed it completely. At about twenty he joined the community of Canons Regular at Mount St Agnes near Zwolle, where his older brother was prior, and he stayed for roughly seventy years. He was ordained, served as sub-prior more than once, and spent the greater part of his working life as a copyist. He copied a complete Bible four times, along with missals and other books, in a clear hand that survives.
He also wrote a good deal himself: chronicles of his own house, sermons to novices, and lives of Groote and the first Brethren, which are the principal source for the movement's early history. None of that would have made him known outside the Low Countries. He is one of the most widely read Christian authors in history because of a small book of four parts, gathered from booklets he had written for novices, which he transcribed into a manuscript in 1441.