From Pope St. John Paul II’s encyclical Fides et Ratio (1984):
In the light of these considerations, the relationship between theology and philosophy is best construed as a circle. Theology’s source and starting-point must always be the word of God revealed in history, while its final goal will be an understanding of that word which increases with each passing generation. Yet, since God’s word is Truth (cf. Jn 17:17), the human search for truth—philosophy, pursued in keeping with its own rules—can only help to understand God’s word better. It is not just a question of theological discourse using this or that concept or element of a philosophical construct; what matters most is that the believer’s reason use its powers of reflection in the search for truth which moves from the word of God towards a better understanding of it. It is as if, moving between the twin poles of God’s word and a better understanding of it, reason is offered guidance and is warned against paths which would lead it to stray from revealed Truth and to stray in the end from the truth pure and simple. Instead, reason is stirred to explore paths which of itself it would not even have suspected it could take. This circular relationship with the word of God leaves philosophy enriched, because reason discovers new and unsuspected horizons.
The fruitfulness of this relationship is confirmed by the experience of great Christian theologians who also distinguished themselves as great philosophers, bequeathing to us writings of such high speculative value as to warrant comparison with the masters of ancient philosophy. This is true of both the Fathers of the Church, among whom at least Saint Gregory of Nazianzus and Saint Augustine should be mentioned, and the Medieval Doctors with the great triad of Saint Anselm, Saint Bonaventure and Saint Thomas Aquinas. We see the same fruitful relationship between philosophy and the word of God in the courageous research pursued by more recent thinkers, among whom I gladly mention, in a Western context, figures such as John Henry Newman, Antonio Rosmini, Jacques Maritain, Étienne Gilson and Edith Stein and, in an Eastern context, eminent scholars such as Vladimir S. Soloviev, Pavel A. Florensky, Petr Chaadaev and Vladimir N. Lossky. Obviously other names could be cited; and in referring to these I intend not to endorse every aspect of their thought, but simply to offer significant examples of a process of philosophical enquiry which was enriched by engaging the data of faith. One thing is certain: attention to the spiritual journey of these masters can only give greater momentum to both the search for truth and the effort to apply the results of that search to the service of humanity. It is to be hoped that now and in the future there will be those who continue to cultivate this great philosophical and theological tradition for the good of both the Church and humanity.
— Fides et Ratio 73-74