Name borrowed from classic Greek music theory as title for an influential harmony of the four canonical gospels composed before 173 CE by Tatian, probably at Rome. Tatian's work may have simply been an expanded revision of an earlier harmony of the three synoptic gospels made by his teacher, Justin Martyr.

Despite the Diatesseron's widespread influence, there is no surviving complete ms. But much of it can be reconstructed from early commentaries & other harmonies in many ancient languages (other than Greek). The Diatesseron influenced early translations of the four gospels into Syriac, Latin, Armenian, Georgian, & Old German. And its harmonized narrative structure became a model for later gospel harmonies from Holland to Persia. But it was eventually suppressed by Greek Orthodox & Roman Catholic church authorities, because its author became the leader of a heretical sect.

The language in which the Diatesseron was originally composed is debatable. A single Greek fragment was found at Dura Europos in eastern Syria, which was destroyed in 257 CE. Stylistic analysis, however, shows the Diatesseron preferred Syriac grammatical constructions in paraphrasing the Greek gospel texts.

In spite of the Diatesseron's tendency to harmonize passages from the four canonical gospels (and perhaps the gospel of Thomas), its readings are taken seriously by modern textual critics. For the copies of the gospels that Tatian used to create his work were obviously written before the mid- 2nd c. CE. Thus, the Diatesseron is often a witness to the very earliest wording of a particular text.

[For details see W. L. Peterson's chapter on "Tatian's Diatesseron" in Helmut Koester, Ancient Christian Gospels: Their History & Development (London /Philadelphia: SCM Press/Trinity Press International, 1990), pp. 403-430].

Other On-line Resources:

• The Text of the Diatesseron - 1895 English reconstruction of Tatian's text from Latin & Arabic translations by Alexander Roberts & James Donaldson (posted by Early Christian Writings).

• The Diatessaron of Tatian - H. W. Hogg's English 1897 translation in vol. 9 of Philip Schaff's Ante-Nicene Fathers (archived by Christian Classics Ethereal Library).

• Greek Fragment of Tatian's Diatessaron from Dura - PDF of 1935 report by C. H. Kraeling on discovery of 3rd c. ms. (Internet Archive).