The Diatessaron is an ancient literary work that combined the four Gospels of the New Testament into a single narrative. The word Diatessaron can be taken to mean “Harmony of Four”; it is a transliteration of the Greek dia tessaron (“through the four Gospels”). The Roman historian Eusebius first came up with the name Diatessaron.
The Diatessaron was compiled around AD 170 by Tatian, an Assyrian Christian apologist and pupil of Justin Martyr. Tatian’s harmony of the Gospels was not the first of its kind, but it was most influential. Fragments of the Diatessaron have been discovered in Greek, Syriac, Arabic, Latin, and many other languages—even Old English. Tatian would have written in either Greek or Syriac, but no one is sure which is the original language of the Diatessaron. No full copy of the Diatessaron has survived intact today, although we can piece together the full text from various sources.
In composing the Diatessaron, Tatian followed the wording of the Gospels closely, but he used a different sequence for arranging verses. He also removed duplicate information—he kept only one of each parallel passage. Thus, the feeding of the five thousand only appears once in the Diatessaron, instead of four times. Tatian also excised some of what were supposed to be contradictions in the Gospels. For example, he omitted the differing genealogies of Matthew 1 and Luke 3. Also left out of the Diatessaron is the pericope adulterae (the story of the woman taken in adultery in John 8:1–11). The end result is a single, shortened narrative of the life of Christ—about three-quarters the size of the four canonical Gospels. The Diatessaron accounts for all but 56 verses of the canonical Gospels.
In the early church, the four Gospels at first circulated independently. Tatian’s Diatessaron brought them all together in one convenient package. Twenty years after Tatian completed his work, Irenaeus, one of the early church fathers, proclaimed the Diatessaron to be authoritative. The Diatessaron became one of the most popular editions of the Gospels ever produced. Through the years it was used by Catholic Christians, Judaic Christians, Syriac Christians, Manicheans, and missionaries. Its greatest impact was in Syria, where for centuries it was the standard text of the gospel before finally being replaced by the Peshitta.
The Diatessaron isn’t without its problems. It seems that Tatian added some material not found in the original four Gospels, such as the extra-biblical story of a light that illuminated the Jordan River at Jesus’ baptism. Some readings in the Diatessaron are attributed by church fathers to the Gospel of the Hebrews, the Gospel of the Ebionites, and other non-canonical works.
As a result of Tatian’s changes to Scripture, some church leaders were opposed to the Diatessaron. Some opposed the man as well—Tatian was a prominent Encratite, a vegetarian ascetic who abstained from all sexual activity. By the fifth century the Diatessaron had fallen out of favor with church leaders.
The chief value of the Diatessaron today is that it provides an early witness to the original Gospels. The four canonical Gospels—Matthew, Mark, Luke, and John—were accepted by the early church as God’s Word, and great care was obviously taken to preserve the texts and make them widely available. As evidence of the early church’s acknowledgement of the Gospels, the Diatessaron holds a prominent position in modern New Testament studies.