From Pope St. John Paul II’s encyclical Fides et Ratio (1984):
It is clear from history, then, that Christian thinkers were critical in adopting philosophical thought. Among the early examples of this, Origen is certainly outstanding. In countering the attacks launched by the philosopher Celsus, Origen adopts Platonic philosophy to shape his argument and mount his reply. Assuming many elements of Platonic thought, he begins to construct an early form of Christian theology. The name “theology” itself, together with the idea of theology as rational discourse about God, had to this point been tied to its Greek origins. In Aristotelian philosophy, for example, the name signified the noblest part and the true summit of philosophical discourse. But in the light of Christian Revelation what had signified a generic doctrine about the gods assumed a wholly new meaning, signifying now the reflection undertaken by the believer in order to express the true doctrine about God. As it developed, this new Christian thought made use of philosophy, but at the same time tended to distinguish itself clearly from philosophy. History shows how Platonic thought, once adopted by theology, underwent profound changes, especially with regard to concepts such as the immortality of the soul, the divinization of man and the origin of evil.
In this work of christianizing Platonic and Neo-Platonic thought, the Cappadocian Fathers, Dionysius called the Areopagite and especially Saint Augustine were important. The great Doctor of the West had come into contact with different philosophical schools, but all of them left him disappointed. It was when he encountered the truth of Christian faith that he found strength to undergo the radical conversion to which the philosophers he had known had been powerless to lead him. He himself reveals his motive: “From this time on, I gave my preference to the Catholic faith. I thought it more modest and not in the least misleading to be told by the Church to believe what could not be demonstrated—whether that was because a demonstration existed but could not be understood by all or whether the matter was not one open to rational proof—rather than from the Manichees to have a rash promise of knowledge with mockery of mere belief, and then afterwards to be ordered to believe many fabulous and absurd myths impossible to prove true”.38 Though he accorded the Platonists a place of privilege, Augustine rebuked them because, knowing the goal to seek, they had ignored the path which leads to it: the Word made flesh.39 The Bishop of Hippo succeeded in producing the first great synthesis of philosophy and theology, embracing currents of thought both Greek and Latin. In him too the great unity of knowledge, grounded in the thought of the Bible, was both confirmed and sustained by a depth of speculative thinking. The synthesis devised by Saint Augustine remained for centuries the most exalted form of philosophical and theological speculation known to the West. Reinforced by his personal story and sustained by a wonderful holiness of life, he could also introduce into his works a range of material which, drawing on experience, was a prelude to future developments in different currents of philosophy.
38 Saint Augustine, Confessions, VI, 5, 7: Corpus Christianorum, Latin series [CCL] 27, 77-78.
39 Cf. ibid., VII, 9, 13-14: CCL 27, 101-102.
— Fides et Ratio 39-40