I once thought of hermits as shaggy recluses notable mainly for their self-obsession and dearth of social skills—people like the Unabomber. Thomas Merton corrected my misconception. "To be really mad, you need other people," he explained. "When you are by yourself you soon get tired of your craziness. It is too exhausting."

A recent book by Peter France, Hermits, has helped to fill in the picture. France gave up a high-profile career with the bbc to lead a contemplative life on a Greek island. He did so not as an act of sacrifice, rather as a quest for the wisdom available only through a life of solitude. Living apart from the press of popular opinion "confers insights not available to society," France concluded.

Saint Anthony of Egypt, the famous Desert Father, chose the hermitic life in deliberate contrast to his upper-crust upbringing. After 20 years locked away, not seeing another human face, Anthony emerged healthy, balanced, and full of sage advice. From then on he alternated between solo retreats and pastoral visits. France likens the pattern to that of scientists who work alone in search of cures for deadly diseases.

You cannot read about hermits, of course, without encountering strangeness. One monk lusted after a beautiful woman. When she died he took his tunic to her tomb and used it to dry the pus from her corpse. Keeping the smell close to him in his cell, he reminded himself, "This is what you lust after—take your fill."

Some monks competed in a kind of ascetic Olympics, testing how long they could go without food, water, or sleep. These, too, had a method to their madness: their privations caused so much suffering that they left no mental void for carnal thoughts to fill.

France relates other stories ...