Heidegger's Bible Handbook: Harmony of the Gospels: Reasons for Four
1. Why would God will the Gospel history to be written by several? Various reasons for the quaternary number of Evangelists.
It pleased the All-Wise God that the Gospel be committed to writing, not by one, but by several, even four sacred writers, both so that by the mouth of multiple witnesses, two eye-witnesses, Matthew and John, two ear-witnesses, Mark and Luke, the truth concerning Christ, the Savior of the World, might be held more certain; and so that a more complete and fuller history might also be on record, with Matthew, Mark, and Luke generally weaving together the matters conducted, and John, the sermons and doctrine; and it would be made manifest what was the sum of the faith of the diverse and harmonious Churches, suppose Jerusalem, in which Matthew; Rome, in which Mark; Antioch, in which Luke; Ephesus, in which John, are said to have preached and written. What reasons, or conjectures, for the quaternary number of Evangelists others advance, as that there are four parts of the earth, throughout the whole of which they declare in a manner that the Church of Christ is extended by the very commencement of their office, as Saint Augustine speaks in de Consensu Evangeliorum, book I, chapter I: that they are as four columns, on which, as if on a squared stone, the structure of the holy faith is raised, as Gregory the Great in book I of his Epistolarum 24 has it: that the quaternary number is squared and solid, and so it befits the solidity and perfection of the Gospels: that, just as in the heavenly temple there are four Cherubim, the chiefs and Sages of God, as it were; so in the earthly Church it was fitting that there be four Evangelists, the chiefs and Cherubim of Christ, as it were: and whatever other things similar to these the ancient and more recent men ingeniously advance: I also add the types and figures of that number, which, reported as thirteen by Lyra in his Proœmia Marci, do not bear to be repeated here: they do not appear to be of such importance that they enter into the number.