The rise of the Protestant Church in the 16th century led to drastic change in the northern Low Countries. In 1580, when Utrecht became a Protestant city, Catholic services were banned and the libraries of the city's cloisters and chapters were confiscated and handed over to the city library. Utrecht became a Protestant stronghold, which is still reflected in the manuscripts and old printed works in the Special Collections.
One prominent figure during the turbulent years of the Reformation was Arnold Buchelius (1565-1641). He converted from Catholicism to Calvanism, was interested in old monuments, heraldry and genealogy and served in governing bodies, one of which was with the Dutch East India Company (VOC).
The over fifty manuscripts and letter collections from his hand in the Special Collections provide a personal look at the life of a Dutch amateur scholar, as well as his relations, in around 1600. His uncle, Huybert Edmond van Buchell (1513-1599) was a canon of Saint Mary's chapter who sympathised with the Reformation. He left some 2,000 books to the city library, including many rare editions in their original binding.
The Utrecht University Library continued to update its collection on the Protestant faith, thanks in part to the legacy of the professor Simon van der Linde (1905-1995) and the extensive collection of the Dutch Reformed Church.
The Reformation body of thought was propagated and studied by a select group of Utrecht professors, who in many cases were also pastors. Based on their archives, we can seem them playing an active role among their contemporaries and participating in the theological and scientific debates of their time.
The most noteworthy figures of the time were Gisbertus Bonnet (1723-1805), Jodocus Heringa (1765-1840), Johannes Jacobus van Oosterzee (1817-1882), Arnold Hendrik de Hartog (1869-1938), Anneaus Marinus Brouwer (1875-1948), Michiel Cornelis van Mourik Broekman (1878-1945), Theodoor Christiaan Vriezen (1899-1981), Arnold Albert van Ruler (1908-1970), Willem Cornelis van Unnik (1910-1978) and Johannes Christiaan Hoekendijk (1912-1975).
There are also archives of professors from other cities, such as Paulus Merula (1558-1607) from Leiden, Petrus Chevalier (1760-1825) from Groningen, and the prolific and influential Johannes Hermanus Gunning, Jr (1829-1905) from Amsterdam and Leiden. The collection also includes the archives of two controversial pastors, Hermann Friedricht Kohlbrugge (1803-1875) and Lambertus Gerardus Cornelis Ledeboer (1808-1863).