"Lying Awake" concerns the quandry of Sister John, a nun who is diagnosed with temporal lobe epilepsy and fears that her inspiration for visionary religious poetry will depart if she undergoes brain surgery. Confounded by the choice between humdrum health and ecstatic disease, she seeks guidance from a priest: "Should I automatically assume that my mystical experiences have been false, or should I stand behind what my heart tells me? Is God asking me to let go of concerns for my health, or is he asking me to let go of my desire for his presence?"

In response, the priest gently chastises her: "You allowed yourself to think that loving God meant enjoying His company, having ecstasies. It was all about you, wasn't it? But loving God is supposed to be all about Him. About trusting him, putting yourself in His hands completely."

Sister John has the surgery and her raptures end, and her faith deepens as she discovers a new kind of love for God -- "the doing kind, not the knowing kind." Sooner or later, most Christians are faced with a less dramatic version of Sister John's basic choice, between pursuing transcendent religiosity (our fantasies of saintliness, which would prove beyond doubt how special we are) and a more natural experience of devotion (in the disciplines of prayer and righteous action). That's why, even though "Lying Awake" is less successful as a novel than as a statement about the nature of religious faith, it enjoys strong sales and great reviews. The book directly addresses a question that plagues contemporary believers, one that most Christian leaders fear to address. We wonder: How can we live as Christians, when nature seems more real than heaven?

Further research on the God part of the brain will press this question. Although it is highly doubtful that science will ever provide an exhaustive explanation of the religious impulse, it is inevitable that science will enlarge our understanding of the biological processes involved in religious experience. Over time, religious people will be forced to acknowledge that they are not special and separate; they are fully a part of the world.

Expect this to cause no shock waves in Buddhism, Hinduism, Taoism or most other Eastern and African religions. Their understandings of divine immanence and transcendence tend to be much more thoroughly integrated into everyday life than ours in the West. (They already know there's a God part of a bamboo shoot, and they're cool with that.) Christianity, however, will experience some healthy shrinking.

Fundamentalism will wither and ideologues will flee. Christians will have to stop using God as a deus ex machina to solve impossible problems, a rhetorical club with which to overpower those who disagree on points of doctrine. The Christian God will emerge more clearly as He revealed Himself in Jesus -- as the suffering one whom Dietrich Bonhoeffer described in his "Letters and Papers From Prison" as He who "lets himself be pushed out of the world onto the cross. He is weak and powerless in the world, and that is precisely the way, the only way, in which he is with us and helps us."

Whatever in Christianity is threatened by neurological research ought to die anyway. Flipping back from the final pages of "The God Part of the Brain" to its first, I reread the dedication, "to the family of God,/...with all my condolences." The first time through, I read this as the impertinent swipe of a smartass. The second time, I looked forward to the day when I will be able to accept his condolences, though not in the way he might hope.

Maya Angelou reads from "The Heart of a Woman"