From Pope St. John Paul II’s encyclical Fides et Ratio (1984):
Christianity’s engagement with philosophy was therefore neither straight-forward nor immediate. The practice of philosophy and attendance at philosophical schools seemed to the first Christians more of a disturbance than an opportunity. For them, the first and most urgent task was the proclamation of the Risen Christ by way of a personal encounter which would bring the listener to conversion of heart and the request for Baptism. But that does not mean that they ignored the task of deepening the understanding of faith and its motivations. Quite the contrary. That is why the criticism of Celsus—that Christians were “illiterate and uncouth”31—is unfounded and untrue. Their initial disinterest is to be explained on other grounds. The encounter with the Gospel offered such a satisfying answer to the hitherto unresolved question of life’s meaning that delving into the philosophers seemed to them something remote and in some ways outmoded.
That seems still more evident today, if we think of Christianity’s contribution to the affirmation of the right of everyone to have access to the truth. In dismantling barriers of race, social status and gender, Christianity proclaimed from the first the equality of all men and women before God. One prime implication of this touched the theme of truth. The elitism which had characterized the ancients’ search for truth was clearly abandoned. Since access to the truth enables access to God, it must be denied to none. There are many paths which lead to truth, but since Christian truth has a salvific value, any one of these paths may be taken, as long as it leads to the final goal, that is to the Revelation of Jesus Christ.
A pioneer of positive engagement with philosophical thinking—albeit with cautious discernment—was Saint Justin. Although he continued to hold Greek philosophy in high esteem after his conversion, Justin claimed with power and clarity that he had found in Christianity “the only sure and profitable philosophy”.32 Similarly, Clement of Alexandria called the Gospel “the true philosophy”,33 and he understood philosophy, like the Mosaic Law, as instruction which prepared for Christian faith34 and paved the way for the Gospel.35 Since “philosophy yearns for the wisdom which consists in rightness of soul and speech and in purity of life, it is well disposed towards wisdom and does all it can to acquire it. We call philosophers those who love the wisdom that is creator and mistress of all things, that is knowledge of the Son of God”.36 For Clement, Greek philosophy is not meant in the first place to bolster and complete Christian truth. Its task is rather the defence of the faith: “The teaching of the Saviour is perfect in itself and has no need of support, because it is the strength and the wisdom of God. Greek philosophy, with its contribution, does not strengthen truth; but, in rendering the attack of sophistry impotent and in disarming those who betray truth and wage war upon it, Greek philosophy is rightly called the hedge and the protective wall around the vineyard”.37
31 Origen, Contra Celsum, 3, 55: Sources Chrétiennes (Paris, 1946ff) [SC]: 136, 130.
32 Dialogue with Trypho, 8, 1: Patrologiæ Cursus completus, Series Græca [PG] 6, 492.
33 Stromata I, 18, 90, 1: SC 30, 115.
34 Cf. ibid., I, 16, 80, 5: SC 30, 108.
35 Cf. ibid., I, 5, 28, 1: SC 30, 65.
36 Ibid., VI, 7, 55, 1-2: PG 9, 277.
37 Ibid., I, 20, 100, 1: SC 30, 124.
— Fides et Ratio 38