"The first three of these modes (literal, allegorical, and moral) were part of Christian tradition as expressed by Origen. St John Cassian (c. 360-435) added the fourth mode (anagogic) in 4th century.[4] His contemporary, St Augustine of Hippo (354-430) used the four fold interpretive method in his explanation of Christian doctrine, On Christian Doctrine. Due to the widespread popularity of "On Christian Doctrine" in the Middle Ages, the four fold method became the standard in Christian biblical exegesis of that period.[5]