Understanding Christianityas greatest mysteries. Christianity is a religion of genuine mysteries, but there are many doctrines that truth-seeking Christians can understand without a degree in theology. This guide examines the teachings and doctrines that are Christianityas foundations, in clear, straightforward language, including the Incarnation, the Atonement, the Holy Spirit, the Lordas Supper; Jesus and his ministrya the missing 30 yearsaand much more.