Christopher West's latest book -- "Fill These Hearts: God, Sex, and the Universal Longing" -- explores the link between sexual and spiritual cravings. West, a former college professor, specializes in making the scholarly teachings of Pope John Paul II's "Theology of the Body" accessible to everyone. In D.C. this week for an event, he lives in Pennsylvania with his wife and five children.

How can sexuality and spirituality have anything to do with each other?

We have this idea that God belongs over here, and sexuality belongs over here, and ne'er the twain shall meet. Well, right at the heart of Christianity is Christ, and Christ is the reconciliation of the spiritual with all things physical in the incarnation -- this crazy idea that Christians have that God took on a body. The great image of Scripture is that of a marriage. The union of man and woman is not just biological; it's something theological. It points to the very mystery of God; it points to the very love of Christ that he has for humanity. Who can't relate to the Bruce Springsteen song "Everybody's Got a Hungry Heart"? We have this hunger for love, and ultimately, that's a spiritual hunger.

How does that fit in with the tradition of Catholic celibacy?

The Bible begins with the marriage of man and woman, and it ends with the marriage of Christ and the church. The ultimate fulfillment of the desires of our heart is not the union of man and woman. That's just the foreshadowing. The ultimate fulfillment of that ache, of that longing, is the union of Christ and the church. The idea of giving up marriage for the kingdom comes from Christ himself. It's an invitation to skip the foreshadowing, to devote all of our hungers to the ultimate union. Now, if the culture is correct -- that sex is ultimate fulfillment -- then to give it up is insanity. But if the union of man and woman is just a foreshadowing of something far greater, then maybe those who are celibate for Christ's sake are actually pointing the whole world to our ultimate fulfillment, to a greater love.

How can traditional morality, which offers strict rules for sex, not be repressive?

If we want to be professional lovers, that's going to take the same kind of discipline as a musician or an athlete. It's a creative discipline; it's not destructive. Anyone can walk up to a piano keyboard and make meaningless noise. I think that's what a lot of sexual choices really amount to -- friction that is not an expression of love. We gain some physical gratification from it, but it's not beautiful; it doesn't lift our spirits. A concert pianist can also walk up to a piano keyboard and spontaneously make beautiful music. But behind that spontaneity we know is a lifetime of discipline and sacrifice and training. The Catholic church is inviting us to a kind of training, an authentic love boot camp.

At your core, what is one of your defining beliefs?

The ache, the longing, the hunger we all experience as human beings -- there is something that corresponds to it. And if we seek it, we will find it.

- Liz Essley