|Agostino Steuco, OSA|
Angel Custodio Vega, OSA, in his book on the Philosophy of Saint Augustine, shows that the term "philosophia perennis" to name the Christian purification and integration of pagan philosophy into a synthesis of unending vitality, begun by Saint Augustine and perfected to the highest degree by Saint Thomas Aquinas, following the same norms and plan of Augustine, was coined by a certain 15th/16th century augustinian: Agustín Steuco.
It appears that Seuco's De perenni philosophia (Google book) was a work much hated by the Protestents.
Wikipedia Father Seuco's polemical and exegetical works had attracted the notice of Pope Paul III, and in 1538 the pope made Steuco bishop of Chisamo on the island of Crete, and librarian of the papal collection of manuscripts and printed works in the Vatican. While he never visited his bishopric in Crete, Steuco did actively fulfill his role as Vatican Librarian until his death in 1548.
While in Rome he authored Old Testament annotations on the Psalms and Job, again relying heavily upon Hebrew sources to help annotate and correct the texts. Also from this period dates a major work entitled the De perenni philosophia, dedicated to Paul III, in which he attempted to show that many of the ideas expounded by the sages, poets, and philosophers from classical antiquity were in essential harmony with the central tenets of the Catholic faith. This work has a slight polemical edge to it, as Steuco crafted a number of his arguments to lend support to several theological positions that had recently come under question in Italy by reformers and critics of the traditional Catholic faith.
Italian Wiki gives a sample list of the ancient authors he treats: e.g. Orfeo , Thales , Pythagoras , Parmenides , Plato , Aristotle , Plutarch, Numenius , the Neoplatonists , the jew Philo , and works like the Chaldean Oracles , the Sibylline Oracles , the hermetic treatises and theosophical fragments.
P.S. Father Vega also mentions Saint Thomas' title of alter Augustinus, to refer to Thomas' completion of the project begun by Augustine of an perennial philosophy. Joseph Ratzinger has repeatedly said in this regard that our present age is in need of another Saint Thomas--alter Thomas--to sift through and purify and appropriate all of the philosophical giants since the enlightenment with the constant and sure measure of the Incarnate Word of God, Jesus Christ.
P.S.S. The Calvanist International recommends Father Seuco's book!