Saint John Paul the Great’s Fides at Ratio turns 20 this year. It’s described by Wikipedia in this way: It “posits that faith and reason are not only compatible, but essential together. Faith without reason, [John Paul II] argues, leads to superstition. Reason without faith, he argues, leads to nihilism and relativism.” Chaput explains the way Fides et Ratio calls everyone to keep an open mind to the metaphysical aspects of life:

Fides et Ratio is a hymn to the transcendent aspirations of human reason. The aim of any true philosophy, it notes, should be to find the unity of truth in all things, an understanding of the whole. This demands an engagement with the classical discipline we call “metaphysics,” which men still study in preparing for the priesthood.

Metaphysics is an exotic word for a very basic subject: the study of the deep truths and harmonies built into the world. Why, for example, does the world exist? Is matter—material reality—all that there is? Or is there something more? Is there a common human nature? What should we make of the many distinct kinds of things that exist in the world, the sheer givenness of their existence, and their goodness and beauty? How should we understand the human person as a distinct sort of reality? After all, a human person has unique abilities. Man is the creature who can know not only physical things, but even himself and others. Man can perceive the truth, goodness, and beauty in things. He’s a creature animated by questions of ultimate meaning, including whether God exists.

Fides et Ratio argues that any culture that ignores man’s ultimate metaphysical questions locks itself in a false and empty immanence. It can no longer approach the question of God. And by this very fact, it will scar the inner life of the human person. As John Paul notes, “Christian Revelation is the true lodestar of men and women as they strive to make their way amid the pressures of an immanentist habit of mind and the constrictions of a technocratic logic.” This message is strikingly contemporary. Our modern universities typically avoid God as a serious subject of inquiry. Without God, or at least some sense of a higher order or meaning to nature, the dignity of the human person is little more than folklore, the residue of pre-Darwinian beliefs. God and the soul are in exile. And that’s because classical philosophy is in exile, to the detriment of genuine learning.

Fides et Ratio also confronts the crisis of truth within the Catholic Church herself. Catholic theology studies the mystery of God revealed in Jesus Christ. This truth is made known to us by the Holy Spirit. It’s not one we come to know by our own natural powers. But good theology depends upon vigorous philosophy, at least in this sense: We can’t think correctly about God’s revelation unless we cultivate a reasonable philosophical attitude toward God, the world, and other human persons.

The benefits of a vigorous cultivation of both philosophy and theology flow both ways. The rigor of philosophical reason, as Benedict XVI said, purifies religion. It prevents religious faith from lapsing into superstition. Theology, in turn, helps philosophers to cultivate an attitude of openness and accountability to all of reality. Far from being anti-intellectual, Catholic theology raises the expectations for human reason. Everything we can come to know is part of the created order and therefore “friendly” to the authentic revelation of God.

Philosophy in the Catholic tradition pays special attention to the ways we speak about God “analogically” from comparison with creatures. The created world around us exists and is good. So, too, God exists and is good—but in an infinitely higher and incomprehensible way. So when God reveals himself to us as the Holy Trinity, he is simultaneously the God of revelation and the God of natural reason, the God of the Bible and the God of the philosophers.

This way of thinking about the harmony of faith and reason is central to the Catholic tradition, from Church Fathers such as Justin and Augustine to medievals such as Bonaventure and Aquinas down to modern Catholic councils, both at Vatican I and Vatican II. This harmony is expressed in the opening lines of Fides et Ratio: “Faith and reason are like two wings on which the human spirit rises to the contemplation of truth.”

In 2015, we inscribed the phrase Fides et Ratio onto the gravestone of John and Marion Shakely, my grandparents. We did this for two reasons. First, to allude to the marriage of my grandfather’s familial Protestantism and my grandmother’s familial Catholicism and in so doing to recognize the healing of Christian divisions. And second, specifically to recognize John Paul II’s Fides et Ratio encyclical, for speaking clearly to a world too ready to think that the particular and complex problems of any particular historical moment are somehow without precedent, and that an authentic, robust faith and reason together can be those “wings on which the human spirit rises to the contemplation of truth” beyond the particulars of any specific and finite generation.