Yet the arrangement of the world rests upon the rationale for this evangelical number: for we recognize the four seasons that the year progresses through and the four corners of the earth that the four guardian angels are assigned to, referring to the Apocalypse.

And although there are said to be four gospels because of the number of the evangelists, even though there is only gospel among them all, as the Lord said: “And this gospel will be preached through the whole globe.” He did not say gospels but “gospel“. The apostle described this too when he says: “If anyone has preached to you a gospel other than what you have received, let them be accursed.” Hence, it is plain that there are certain four books of the gospels, but one gospel is counted in these four books. And for that reason one must not be prejudiced should we sometimes say —gospels— because of the number of evangelists or when we name the gospels in this way as the most important books or when we designate the number of the evangelists according to the usual custom of the majority. Indeed we both confess and believe that there is one true gospel according to the authority of the Lord or even the apostle. — Prologue, Section 10 and 11.