In the second century, well before the canonical gospels took their present form, Tatian wove from the four gospels and one or more Judaic-Christian gospels one harmonized account of the life of Christ, the Diatessaron. He eliminated duplicate passages, deleted or reconciled contradicting verses, and harmonized parallels. Tatian's Diatessaron became the standard gospel among the Syriac-speaking Christians of Syria and Mesopotamia up till the fifth century. Its text spread from China to England and possibly Iceland, becoming one of the oldest witnesses to the gospels.

The Earliest Life of Christ is an English translation of the Diatessaron based on the Arabic version, itself a translation from the lost Syriac.

"J. Hamlyn Hill's English translation of the Arabic Diatessaron remains a milestone in scholarship, for it was the first translation of a Diatessaronic text into English. Although based on Augustinus Ciasca's imperfect 1888 edition of the Arabic Diatessaron, Hill's translation nevertheless opened the mysteries of the Diatessaron to the English-speaking world for the first time."--William Petersen, author of Tatian's Diatessaron, (1994).

"In the history of the [New Testament] versions, as well as in the early phase of textual developments of the New Testament as a whole, there is no greater and more important name than Tatian"--Arthur Vööbus, Early Versions of the New Testament (1954).