TATIAN: The DiatesseronAbbreviations: D = Diatesseron / Sinai text = S / Cureton = C / Peshitta = PIntroduction: The earliest evidence of a lectionary system may be the gospel of Mt. Apparently its constructionfollows the Jewish cycle of Torah readings. It is not a literary but a liturgical genre, as a lectionary book, aseries of gospels used in lectio continua at the worship. The first Christians used a Jewish lectionary cycle ofreadings for 1 or 3 years. The need to include the gospel stories of Jesus into the life of the Jewish-Christiancommunity may have culminated in the creation of a gospel harmony. The D. may have been an attempt tosolve the lectionary crisis and put Jesus' life into a continuous narrative divided into 55 chapters, what nearlycoincides with the numbers of weeks in a year plus a few extra for big feasts. According to one of the laws ofBaumstark certain feasts or seasons keep the original practice. So do we find on Good Friday in the WestSyriac Church the practice of reading the gospel in a harmony.We find in the 2nd century 3 other stimuli which led to harmonisation. There was the criticism of Christianityby pagans, such as Celsus, who mocked the new religion by pointing out the inconsistencies among thegospels. A possible response was to claim only one gospel was authoritative, as Marcion had done. Anotheranswer, adopted by Tatian, was to reconcile the divergent accounts by conflating them into a single account.Another stimulus was the scholarly historical method of the period: when confronted with inconsistent orcontradictory information, that which is judged most reliable is adopted as the framework, and the other detailsare fitted in around. Secular historians in antiquity did the same (e.g., Josephus). The third motive, unique toTatian, was his philosophical understanding of truth as unitary. He proclaimed himself to be "the herald oftruth" and mocked the Greeks in his Oratio ad Graecos for their contradictory teachings and schools; this ...