FAGNANI, PROSPERO. — Canonist and theologian, born at S. Angelo in Vado in 1587, died in Rome in 1678. He graduated in utroque iure at Perugia (1618) and taught canon law at the University of Rome.
Secretary of the S. Congregation of the Council at only twenty-two years of age, he subsequently held the same office in four other Congregations (Bishops and Regulars, apostolic visitation, the affairs and reform of Regulars, indulgences). At the same time, he was called to various other Curial duties and held important positions in eleven dicasteries simultaneously. Gregory XV chose him as his collaborator in drafting the bull Aeternis Patris concerning the election of the Supreme Pontiff. Blinded at only forty-four years of age, he continued his curial and scholarly activity and was called, by antonomasia, «doctor caecus oculatissimus».
His classic commentaries on the Decretals (Ius Canonicum seu commentaria absolutissima in quinque libros decretalium, Rome 1651, and subsequent editions, 5 vols., in-fol.), composed at the command of Alexander VII and enriched with important material drawn from the decisions of the S. Congregation of the Council and various other Congregations, earned him an eminent place among the post-glossators; they still enjoy considerable authority and are particularly useful for the history of post-Tridentine ecclesiastical discipline. In moral theology, he professed probabiliorism and wrote a short work against probabilism, for which s. Alfonso defines him: «magnus rigoristarum patet».