From Pope St. John Paul II’s encyclical Fides et Ratio (1984):
This rapid survey of the history of philosophy, then, reveals a growing separation between faith and philosophical reason. Yet closer scrutiny shows that even in the philosophical thinking of those who helped drive faith and reason further apart there are found at times precious and seminal insights which, if pursued and developed with mind and heart rightly tuned, can lead to the discovery of truth’s way. Such insights are found, for instance, in penetrating analyses of perception and experience, of the imaginary and the unconscious, of personhood and intersubjectivity, of freedom and values, of time and history. The theme of death as well can become for all thinkers an incisive appeal to seek within themselves the true meaning of their own life. But this does not mean that the link between faith and reason as it now stands does not need to be carefully examined, because each without the other is impoverished and enfeebled. Deprived of what Revelation offers, reason has taken side-tracks which expose it to the danger of losing sight of its final goal. Deprived of reason, faith has stressed feeling and experience, and so run the risk of no longer being a universal proposition. It is an illusion to think that faith, tied to weak reasoning, might be more penetrating; on the contrary, faith then runs the grave risk of withering into myth or superstition. By the same token, reason which is unrelated to an adult faith is not prompted to turn its gaze to the newness and radicality of being.
This is why I make this strong and insistent appeal—not, I trust, untimely—that faith and philosophy recover the profound unity which allows them to stand in harmony with their nature without compromising their mutual autonomy. The parrhesia of faith must be matched by the boldness of reason.
— Fides et Ratio 48