J. R. Tolkien, the author of "Lord of the Rings," was very influential in C.S. Lewis' conversion to Christianity. As a man of considerable imagination, he was not one to easily denigrate this faculty.

But he knew its limits. One night, after hours of listening to Lewis object to certain aspects of the faith, Tolkien suggested to him that his problem was not so much one of faith as it was of imagination: "Your inability to understand stems from a failure of imagination on your part."

There's something important in that statement. It tells us that the seat of our faith does not lie within our imaginations and that we cannot sustain our faith by our imaginations. To forget this leaves us open to a dangerous confusion. Here's an example:

Recently, at a retreat, a woman approached me for advice. This was her quandary: She felt full of faith and doubt both at the same time.

She began by telling me that she was, in her mind, a very orthodox Roman Catholic; somewhat pious even. Yet, try as she might, she could not believe that Jesus physically rose from the dead, nor that we will one day rise from the dead.

"I believe," she told me, "that Jesus lived on after his death in some way, but his body remained in the grave. I can't picture it coming back to life. I have the same problem imagining our own resurrection from the dead. I believe in immortality, but not in resurrection. If I can't believe that, and I can't, and I know I never will, does that make me an atheist? Am I losing my faith?"

At first glance it might appear that she is losing her faith, at least in that she is seemingly unable to believe in some non-negotiable parts of the creed. That judgment, though, can be simplistic.

My advice to her was somewhat in line with Tolkien's comment to C. S. Lewis. Her struggles were more with her imagination and its incapacity to give her a mental picture of resurrection than they were with believing in the Resurrection itself. What's the difference?

Imagine yourself lying in bed some night. You've just had a wonderful prayer-time and you're flooded with feelings and images about God. On this particular night, you have strong, clear feelings that God exists, you have no faith doubts, you feel the reality of the divine.

But imagine another night, a darker one. You wake up from a fitful sleep and are suddenly overwhelmed by the sense that you no longer believe in God. You try to convince yourself that you still believe, but you cannot. Every attempt to imagine that God exists and to feel his presence comes up empty. You feel empty and you feel the emptiness of the world itself.

Try as you like, you cannot shake the feeling that you no longer believe. Try as you like you can no longer imagine God as existing nor can you give yourself any feeling that God exists.

Does this mean that on one of these nights you have a strong faith and on the other you have a weak one? Not necessarily. It can just as easily mean that on the one night you have a strong imagination and on the other you have a weak one. One night you can imagine the presence of God and on the other night you cannot. But imagination isn't faith.

Daniel Berrigan, with his usual color, puts this rather crassly, but accurately: He'd been asked: Where does your faith live? In your head or in your heart? His answer?

Your faith, he assures us, is rarely where your head is at, and even less where your heart is at. Your faith, he brilliantly states, is where your [rear end] is at! Within what commitments are you sitting? What holds you, morally and otherwise?

Our actions, our charity, our morality, our commitments determine whether we believe or not, but the posterior is a better indicator of where we stand with faith than are the head and the heart. We understand this because we all have experiences wherein we find ourselves inside of certain commitments (marriage, family, church) even though, at times, our heads and our hearts are not there. Still, we're there!

Why? The head tells us this doesn't make sense, the heart no longer has the type of feelings that would keep us there, but we remain there, held by something deeper, beyond what we can explain or feel. This is where faith lives. This indeed is what faith means.

The woman who sought spiritual counsel from me claimed that she did not believe in the Resurrection but, by almost all indicators, she lived her life in function of it. Her problem was only that her imagination could not picture it. Like all of us, she suffers the poverty of a finite imagination trying to picture the infinite.

But God cannot be pictured. And so a weak imagination isn't the same thing as a weak faith.

Oblate of Mary Immaculate Father Ronald Rolheiser is a specialist in the field of spirituality and systematic theology. His website is www.ronrolheiser.com.