Girolamo Casanate was born in Naples in 1620 to a family of Spanish origin, from Aoiz in Navarre. He completed his studies in his hometown, graduating in 1635 in utroque iure and, although he had shown a propensity for religious life since he was a boy, to please his father he worked as a lawyer before finally being able to undertake ecclesiastical life. Called to the Holy See, he was entrusted with prestigious roles in papal legations as governor of Sabina, Fabriano, Camerino, Ancona and everywhere else his government was distinguished both for its civil and social commitment and for the wise reorganization policy of the territories entrusted to him. In 1658 he was appointed Inquisitor in Malta, a position of great responsibility, as it consisted not only in defending Catholic orthodoxy from heterodox attacks, but also in safeguarding the interests of the Holy See with respect to the Order of Jerusalem. Even in this case, with skill and prudence he will be able to heal the fractures and usefully serve the interests of the Church.
The numerous tasks that were gradually entrusted to him upon his return to Rome from Malta in 1663 (Secretary of the Congregation of Rites, of the Congregation De propaganda fide, Assessor of the Holy Office, protector of various religious orders and finally Librarian of the Holy Roman Church) did not prevent him from dedicating himself to his beloved studies, as well as to his activity as a bibliophile, a passion that he inherited from his father Mattia together with the precious library, a bibliographical collection of 1639 volumes including manuscripts, incunabula and rare editions of the 16th and 17th centuries: sacred, liturgical and patristic texts; legal texts, trial records, Decisiones of various tribunals including that of the Sacred Roman Rota. And again, in line with the culture of the seventeenth century, wide-ranging historical works, political treatises, geographical works, Greek and Latin classics, works by representatives of the new science such as Kepler, Della Porta, Cardano.
The “libraria” was enriched and increased by Casanate to such an extent that upon his death in 1700, he was able to leave to the Dominican fathers, as the first nucleus of the library to be established, a collection of over 25,000 volumes, including works of every genre and from every field of human knowledge, a true mare magnum that aroused the admiration of Italian and foreign scholars.