From Pope St. John Paul II’s encyclical Fides et Ratio (1984):
It may help, then, to turn briefly to the different modes of truth. Most of them depend upon immediate evidence or are confirmed by experimentation. This is the mode of truth proper to everyday life and to scientific research. At another level we find philosophical truth, attained by means of the speculative powers of the human intellect. Finally, there are religious truths which are to some degree grounded in philosophy, and which we find in the answers which the different religious traditions offer to the ultimate questions.27
The truths of philosophy, it should be said, are not restricted only to the sometimes ephemeral teachings of professional philosophers. All men and women, as I have noted, are in some sense philosophers and have their own philosophical conceptions with which they direct their lives. In one way or other, they shape a comprehensive vision and an answer to the question of life’s meaning; and in the light of this they interpret their own life’s course and regulate their behaviour. At this point, we may pose the question of the link between, on the one hand, the truths of philosophy and religion and, on the other, the truth revealed in Jesus Christ. But before tackling that question, one last datum of philosophy needs to be weighed.
Human beings are not made to live alone. They are born into a family and in a family they grow, eventually entering society through their activity. From birth, therefore, they are immersed in traditions which give them not only a language and a cultural formation but also a range of truths in which they believe almost instinctively. Yet personal growth and maturity imply that these same truths can be cast into doubt and evaluated through a process of critical enquiry. It may be that, after this time of transition, these truths are “recovered” as a result of the experience of life or by dint of further reasoning. Nonetheless, there are in the life of a human being many more truths which are simply believed than truths which are acquired by way of personal verification. Who, for instance, could assess critically the countless scientific findings upon which modern life is based? Who could personally examine the flow of information which comes day after day from all parts of the world and which is generally accepted as true? Who in the end could forge anew the paths of experience and thought which have yielded the treasures of human wisdom and religion? This means that the human being—the one who seeks the truth—is also the one who lives by belief.
27 Cf. Second Vatican Ecumenical Council, Declaration on the Relations of the Church with Non-Christian Religions, Nostra Aetate, 2.
— Fides et Ratio 30-31