One of the most valuable elements in the Epistles of St. Paul is their revelation of the writer's spiritual life. While they are necessarily doctrinal and theological, dealing with the fundamental realities of the Christian religion, they are also intensely personal, and express very much of the Apostle's own experience. They depict in a marked degree the sources and characteristics of the spiritual life. This is especially seen when the various prayers, thanksgivings, doxologies, and personal testimonies are considered.