Christian faith is built on presence. Whether in the pillar of fire, the still small voice, or the incarnate Son, God has been Emmanuel, "with us." He has promised never to leave or forsake us. In thousands of hymns, we have sung of an experienced intimacy with God in Christ. We have prayed, wept, and rested in his presence.

For a committed Christian, then, nothing is more devastating than divine absence, spiritual loneliness, the experience of our prayers hitting a ceiling of brass.

Yet when the sixteenth-century mystic John of the Cross identified a similar phenomenon—this spiritual desolation called the "dark night of the soul"—he insisted that it is an important spiritual discipline. The dark night, said John, is a tortuous but fruitful path to union with God. For the great Carmelite, the dark night was just one part of an elaborate theology that penetrated beyond the realm of our senses and reason to come before God as The Awesome Unknown.

Today few subscribe to John's view. ...