In December 1945, two Egyptian fellahin, digging for natural fertilizer in the Nile River valley unearthed a sealed storage jar. The jar proved to hold treasure of an unexpected sort- a collection of some fifty-two ancient manuscripts, most of which reflect the teachings of a mystical religious movement we call Gnosticism (from the Greek word gnosis, "knowledge"). The texts are also, with few exceptions, Christian documents, and thus they provide...