Has this type of Harmonious Merger of the Gospels existed before?
Long before there were the four Gospels that we have today, placed side-by-side as a collection in the New Testament, the four accounts of Matthew, Mark, Luke and John were combined in a merged harmony called, the “Diatessaron“, in about 160 CE. The creator of that unified Gospel account was a man named Tatian, who was a student of Justin Martyr in Rome. After Justin died, Tatian continued his school, until he came into conflict with the Church of Rome, and left the city.
It should be noted that in the year 160 CE, when Tatian was compiling his merger, there were many Gospel accounts, and collections of the sayings and teachings of Jesus Christ, being circulated throughout the growing church. By some accounts, there were more than 20 such “Gospels”. Of those, Tatian used just four, the same four accounts that are found in every New Testament of Jesus Christ today. Why he used these four Gospel accounts, in favor or lieu of the others, was likely because he knew John’s Gospel to be inspired, and perhaps he used the other three because they were so similar.