The screams began at midnight.

I bolted to my feet, still in my sleeping bag. After an eight-mile, rain-drenched solo hike on a wilderness island in Lake Superior, I had reached the deserted campground at dusk. It was early in the season, cold and buggy. Most backpackers would wait until later in June to arrive, when the weather was more favorable and the mosquitoes weren't quite so ferocious. But I was hoping for quiet and solitude, away from cell phones, e-mail, and the demands of family life. After stripping off my soaked clothing and changing into dry longjohns, I heated hot water for coffee and ate some gorp, then fell into an exhausted rest.

Until the screaming.

I reached for my pocketknife and stumbled over my gear, peering out into the foggy dark. Now, it was quiet, the deep silence of wilderness.  The only sound was my adrenaline-crazed heart, thumping loudly. Clutching my knife, I pulled my sleeping bag around me and convinced myself I had been dreaming. But in moments, the screams started again. Something wet trickled down my hand --in my terror, I had cut myself. Sucking the wound, I felt pure fear. And I realized I was helpless to do anything to alleviate it.

In The Wisdom of Wilderness, the final book Gerald May penned before his death, he writes about his own baptism of terror. He awakes in his tent, alone—but not alone, because a growling bear is brushing against the canvas. "For the first time in my life, I am experiencing pure fear," he writes. "I am completely present in it, in a place beyond all coping because there is nothing to do." When the bear leaves, he experiences overwhelming gratitude. "Fear, like any other strong emotion, can make you exquisitely conscious of living, perfectly aware of being ...