Although formally addressed to the bishops of the Catholic Church, Pope John Paul II's 13th Encyclical, Fides et Ratio [“Faith and Reason”], speaks to cultural problems found far beyond the Church's boundaries. These problems revolve around a single, urgent question: Can human beings know the truth of things?

People who don't spend much (or any) time around intellectuals shake their heads and ask: Why is that even considered a question? Of course, they say, I know that some things are true. I know that that is a chair and that this is a glass of wine; that Gettysburg was fought on July 1-3, 1863, and that D-Day was June 6, 1944; that freedom is better than slavery and that children must never be tortured. There are truths of all sorts and we can know them. What's all the fuss about?

But you won't find that robust confidence in the human capacity to know the truth in the places that shape much of our high culture—our colleges and universities. And the leading skeptics about there being anything called “the truth” can be found in university philosophy departments. This, too, strikes many people as bizarre. Isn't truth-seeking what philosophy is for?

Well, yes, once upon a time. During the past two centuries, though, philosophers have been intensely preoccupied with how we can know anything, to the point where philosophy has become thinking-about-thinking-about-thinking, rather than thinking about the truth of things. This intense self-absorption has taken several forms. The most prominent today argues that truth is culturally constructed “all the way down.” There is your truth (based on your cultural conditioning) and my truth (similarly “constructed”), but there is no such thing as the truth.

All of which, John Paul II suggests, has made for immense human suffering. Ideas, as always, have consequences. If there is only your truth and my truth and neither of us recognizes a standard by which to judge whose truth is truer (so to speak), then there is only one way to settle things when we disagree: you will impose your will on me, or I will impose mine on you. Why has the history of the 20th century been replete with political violence? One crucial reason, the Pope proposes, is that philosophers have lost their nerve and their sense of vocation.

Fides et Ratio argues that it's time to recover a sense of the awe and wonder with which real philosophy begins, and to reopen the great questions that philosophy is meant to examine: Why is there something rather than nothing? How can I tell good from evil? What is happiness and what is illusion?

The human mind, the Pope suggests, has a built-in affinity for these questions. To deny that the questions are meaningful (as many contemporary philosophers do) not only demeans philosophy; it demeans the human spirit. You are greater than you imagine, John Paul is telling his fellow philosophers (and the rest of us). Recover your nerve. Don't retreat into a bunker without windows or doors. Don't prematurely close yourself to an encounter with the realm of the transcendent, with the mystery that bounds reality.

Fides et Ratio is also a challenge to Christian believers. Faith without reason risks decaying into superstition. Christian faith is something to be thought about and analyzed, not simply experienced. Here the Pope offers a powerful citation from St. Augustine: “Believing is nothing other than to think with assent. Believers are also thinkers; in believing they think and in thinking they believe. If faith does not think, it is nothing.”

It's a quote that might usefully be posted over every Catholic classroom in America, mounted over every religious education director's office, and attached to every preacher's notepad.

Fides et Ratio is also an appropriate marker for John Paul II's 20th anniversary. A pontificate that began with the great antiphon, “Be not afraid!” continues into its third decade with a related challenge: “Be not afraid of reason!” That the Catholic Church is the world's premier defender of human reason on the edge of the 21st will strike many of the makers of modern culture as ironic at best, and absurd at worst.

But as Walter Cronkite used to say, “That's the way it is.”

George Weigel is a senior fellow of the Ethics and Public Policy Center in Washington, D.C.