What is the "Augustinian hypothesis"?

Augustine of Hippo, a 5th-century Christian church bishop suggested an order to the writing of the three synoptic Gospels, "Now, those four evangelists whose names have gained the most remarkable circulation over the whole world, and whose number has been fixed as four, ...are believed to have written in the order which follows: first Matthew, then Mark, thirdly Luke...". The theory is that Matthew was written first, and Mark and Luke were written based on the work of the Gospel of Matthew.

The Christian Gospels of Matthew, Mark and Luke are often referred to as the "synoptic Gospels" because of the literary overlap and similarities seen in the verses of each Gospel. "The Gospel According to John" is not included in the synoptic Gospels, since it doesn't follow or fit with the narrative of the other three. Modern theological writers have questioned the order of writing that Augustine of Hippo sent down. Based on literary analysis, some scholars placed the Gospel of Mark as the earliest of the Gospels, based on the "primitive" wording used.

Numerous theories of the writing of the Christian Gospels, including the "Q source" and "Four-document" hypothesis have been set forth by scholars. The "Q source" is an earlier, as yet undiscovered, document that the other synoptic Gospels were derived from. The "Four-document" hypothesis has at least 4 different pre-Gospel documents used to create the current synoptic Gospels.