Diatessaron

The Diatessaron (c 160–175) is the most prominent Gospel harmony created by Tatian, an early Christian apologist and ascetic. The term "diatessaron" is from Middle English ("interval of a fourth") by way of Latin, diatessarōn ("made of four "), and ultimately Greek, διὰ τεσσάρων (dia tessarōn) ("out of four"; i.e, διά, dia, "at intervals of" and tessarōn, "four"). Tatian combined the four gospels—Matthew, Mark, Luke, and John—into a single narrative.

Tatian's harmony follows the gospels closely in terms of text but puts the text in a new, different sequence. The four gospels differ from one another; like other harmonies, the Diatessaron resolves contradictions. It also omits both the contradictory genealogies in Matthew and Luke. In order to fit all the canonical material in, Tatian created his own narrative sequence, which is different from both the synoptic sequence and John's sequence. Tatian omitted duplicated text, especially among the synoptics. The harmony does not include Jesus' encounter with the adulteress (John 7:53–8:11), a passage that is generally considered to be a spurious late addition to the Gospel of John, with the Diatessaron itself often used as an early textual witness to support this. No significant text was added.

Only 56 verses in the canonical Gospels do not have a counterpart in the Diatessaron, mostly the genealogies and the Pericope Adulterae. The final work is about 72% the length of the four gospels put together (McFall, 1994).

In the early Church, the gospels at first circulated independently, with Matthew the most popular. The Diatessaron is notable evidence for the authority already enjoyed by the four gospels by the mid-2nd century. Twenty years after Tatian's harmony, Irenaeus expressly proclaimed the authoritative character of the four gospels. The Diatessaron became a standard text of the gospels in some Syriac-speaking churches down to the 5th century, when it gave way to the four separate Gospels, in the Peshitta version.