In 1644, the famous Dutch scholar Nicolas Heinsius wrote to his friend Johannes Fredericus Gronovius that there were only two important libraries in Antwerp: that of the Jesuits and that of Balthasar Moretus II, the most important printer of his time, who had supplied him with some manuscripts of Ovid. At that point the catalogue of Moretus’s library comprised 2985 titles, nearly 400 more than the library of Leuven University with its 2600 titles. Heinsius tried several times to convince Moretus to sell his library but, fortunately for Antwerp, Moretus refused to do so. In this article I will demonstrate why we should be so delighted with Moretus’s decision to keep his library intact and preserve it for the future.