1.1: On the authority of the Gospels:
Augustine begins by noting that the Gospels are preeminent among the sacred writings.
The first Christian preachers were the apostles who were eyewitnesses of Jesus’s ministry.
Two of the apostles, Matthew and John, wrote Gospels. Those who were not apostles, Mark and Luke, made use of reliable information to compose their trustworthy Gospels.
Beyond the four Evangelists, no others composed written accounts of the life of Jesus which had canonical authority as Holy Books. So, Augustine rejects the apocryphal gospels.
These non-canonical were those “which the catholic and apostolic rule of faith and sound doctrine condemned [quae catholica atque apostolica regula fidei et sana doctrina condemnat].” Thus, we see Augustine’s appeal to the “rule of faith.”
1.2: On the order of the evangelists, and the principles on which they wrote.
Augustine suggests that there are four “fixed” Gospels, since there are four divisions of the world (presumably, North, South, East, and West), as a “mystical sign” of how the Christian faith would spread worldwide.
He further suggests they were written in the chronological order: Matthew, Mark, Luke, John.
In this way the first and last evangelists were apostles (Matthew and John), who supported the evangelists who were not apostles (Mark and Luke) on either side “like sons who were to be embraced.”
Of the four Matthew was originally written in Hebrew and the others in Greek. Each evangelist received “the gift of inspiration [unicuique inspiratum].”
Each Evangelist kept “a certain order of narration proper to himself.”
Matthew stressed the “royal lineage” of the Lord.
Mark “follows him closely, and looks like his attendant and epitomizer [pedissequus et breviator eius].” Mark has “little to record” by himself that is not included in the other Gospels, especially Matthew.
Luke, on the other hand, present the Lord according to his “priestly lineage and character.” In his genealogy, he traces the Lord’s line not through Solomon (as Matthew does) but through David’s son Nathan, who was not a king.
Augustine’s introduction stresses the apostolic authority of the canonical Gospels. The canonical Gospels are consistent with the regula fidei. With respect to their chronological order, he puts forward what will become knowns as the “Augustinian Hypothesis” that the Gospels were written in their canonical order: Matthew, Mark, Luke and John. He sees a close connection between Matthew and Mark which present the Lord Jesus as King, alongside Luke, who present him as a Priest. We might note that he is seemingly among the first to group the first three Gospels (the so-called Synoptic Gospels) as distinct from John.