The Protestant theologian Paul Tillich once commented that “faith” is the most misunderstood word in the religious vocabulary. I’m increasingly convinced that he was right about this.

Again and again, my agnostic, atheist and secularist interlocutors tell me that faith is credulity, naïvete, superstition, assent to irrational nonsense, acceptance of claims for which there is no evidence, etc. They gladly draw a sharp distinction between faith so construed and modern science, which, they argue, is marked by healthy skepticism, empirical verification, a reliable and repeatable method, and the capacity for self-correction.

How fortunate, they conclude, that the Western mind was able finally to wriggle free from the constraints of faith and move into the open and well-lighted space of scientific reason. And how sad that, like a ghost from another time and place, faith continues to haunt the modern mind and to hinder its progress.

Recently, Pope Benedict XVI announced that, commencing next fall, the church will celebrate “a year of faith.” A good way to mark that announcement is, it seems to me, a clarification of what Catholics do and don’t mean by that word.

I will begin with an analogy. If you are coming to know a person, and you are a relatively alert type, your reason will be fully engaged in the process. You will look that person over, see how she dresses and comports herself, assess how she relates to others, Google her and find out where she went to school and how she is employed, ask mutual friends about her, etc. All of this objective investigation could take place even before you had the opportunity to meet her. When you finally make her acquaintance, you will bring to the encounter all that you have learned about her and will undoubtedly attempt to verify at close quarters what you have already discovered on your own.

But then something extraordinary will happen, something that will, inevitably, reveal to you things that you otherwise would never know: She will speak. In doing so, she will, on her own initiative, disclose her mind, her heart, her feelings to you. Some of what she says will be in concord with what you have already found out, but much of it — especially if your relationship has deepened and your conversations are profound and intimate — will be new, wonderful, beyond anything you might have discovered on your own.

But as she speaks and as you listen, you will be faced with a choice: Do you believe her or not? Again, some of what she says you might be able to verify through your own previous investigation, but as she speaks of her feelings, her intentions, her aspirations, her most abiding fears, you know that you have entered a territory beyond your capacity to control. And you have to decide: Do you trust her or not?

So it goes, whether we like it or not, anytime we deal with a person who speaks to us. We don’t surrender our reason as we get to know another person, but we must be willing to go beyond our reason; we must be willing to believe, to trust, to have faith.

Trusting the person of God

This is, I think, an extremely illuminating analogy for faith in the theological sense. For Catholics, authentic faith never involves a sacrifice of the intellect. God wants us to understand all we can about him through reason.

By analyzing the order, beauty and contingency of the world, there is an enormous amount of “information” we can gather concerning God: his existence, his perfection, the fact that he is endowed with intellect and will, his governance of the universe, etc. If you doubt me on this, I would invite you to take a good long look at the first part of Thomas Aquinas’s “Summa theologiae.”

One of the truths that reason can discover is that God is a person, and the central claim of the Bible is that this person has not remained utterly hidden but has, indeed, spoken. As is the case with any listener to a person who speaks, the listener to the divine speech has to make a choice: Do I believe him or not?

The decision to accept in trust what God has spoken about himself is what the church means by “faith.” This decision is not irrational, for it rests upon and is conditioned by reason, but it presses beyond reason, for it represents the opening of one heart to another.

In the presence of another human being, you could remain stubbornly in an attitude of mistrust, choosing to accept as legitimate only those data that you can garner through rational analysis; but in so doing, you would close yourself to the incomparable riches that that person might disclose to you. The strict rationalist, the unwavering advocate of the scientific method, will know certain things about the world, but he will never come to know a person.

The same dynamic applies to our knowledge of God, the supreme person. The Catholic Church wants people to use reason as vigorously and energetically as possible — and this very much includes scientific reason. But then it invites them, at the limits of their striving, to listen, to trust, to have faith.

Father Robert Barron is the founder of the global ministry, Word on Fire and the Francis Cardinal George Professor of Faith and Culture at the University of St. Mary of the Lake in Mundelein, Ill.