Giacinto (Hyacinth) D'Urso (1913-2002), Dominican friar of the Province of San Marco and Sardegna (later the Roman Province), is regarded by many Italian commentators as the foremost expert on the mysticism of Catherine of Siena. After his ordination in 1936 he obtained a doctorate in theology from the Angelicum in Rome. He served the Order in various capacities as novice master, prior, pastor, preacher and, for a time, professor of theology at the Angelicum. For many years he was the editor of the acclaimed Dominican spirituality journal Rivista di Ascetica e Mistica and was a lifelong student of the spirituality of Fra Angelico, St. Antoninus, Blessed Angela of Foligno, but in a particular way of the thought of St. Catherine of Siena of whom he was a devoted Caterinato. The Bibliografia analitica di S. Caterina da Siena 1901-2000 lists 107 scholarly articles written by Father D'Urso between 1940 and 2000. Some of the more important ones were collected and published by the National Center of Catherinian Studies in Rome under the title Il genio di Santa Caterina (1971). He and Alvaro Grion, OP, were the major theological contributors to the official positio commissioned by the Vatican in preparation for Catherine being proclaimed Doctor. It was not the last time that Fr. D'Urso's expertise was to be put at the service of the universal Church as the echo of his voice can be heard in the apostolic letter of Paul VI mentioned above as well as in John Paul II's apostolic letter Amantissima Providentia (1980) for the sixth centenary of Catherine's death. In 1970, the year Catherine was proclaimed Doctor, Fr. D'Urso wrote his magnum opus, a 113-page article, in the form of notes, on the life and teaching of the Sienese saint in the review Temi di Predicazione published by the Dominicans in Naples. It was only in this article, a translation of which is the book you are now holding, that he ever attempted a comprehensive exposition of her teaching. D'Urso brought to this work a classical theological training, knowledge of mysticism in general, his Dominican vocation, and an ardent love of Catherine. He is careful and thorough in his summaries and analyses; his conclusions are balanced and reliable. His style is literary, succinct, and dense. Most important, his scholarship reveals new depths to Catherine's thought, making for a new appreciation of her on the 40th anniversary of Paul VI's proclamation. Thomas McDermott, OP Author, Catherine of Siena. Spiritual Development in Her Life and Teaching