Tatian, however, is claimed by apologists as a witness for the existence of our Gospels—more than this he could not possibly be—principally on the ground that his Gospel was called by some Diatessaron [———] or "by four," and it is assumed to have been a harmony of four Gospels. The work is no longer extant and, as we shall see, our information regarding it is of the scantiest and most unsatisfactory description. Critics have arrived at very various conclusions with regard to the composition of the work. Some of course affirm, with more or less of hesitation nevertheless, that it was nothing else than a harmony of our four canonical Gospels;(3) many of these, however, are constrained to admit that it was also partly based upon the Gospel according to the Hebrews.(4) Some maintain that it was
a harmony of our three Synoptics together with the Gospel according to the Hebrews;(1) whilst many deny that it was composed of our Gospels at all,(2) and either declare it to have been a harmony of the Gospel according to the Hebrews with three other Gospels whose identity cannot be determined, or that it was simply the Gospel according to the Hebrews itself,(3) by which name, as Epiphanius states, it was called by some in his day.(4)
Tatian's Gospel, however, was not only called Diatessaron, but, according to Victor of Capua, it was also called Diapente [———] "by five,"(5) a complication which shows the incorrectness of the ecclesiastical theory of its composition.
Tischendorf, anxious to date Tatian's Gospel as early as possible, says that in all probability it was composed earlier than the address to the Greeks.(6) Of this, however, he does not offer any evidence, and upon
examination it is very evident that the work was, on the contrary, composed or adopted after the Oration and his avowal of heretical opinions. Theodoret states that Tatian had in it omitted the genealogies and all other passages showing that Christ was born of David according to the flesh, and he condemned the work, and caused it to be abandoned, on account of its evil design.(1) If the assumption be correct, therefore, as Tischendorf maintains, that Tatian altered our Gospels, and did not merely from the first, like his master Justin, make use of Gospels different from those which afterwards became canonical, he must have composed the work after the death of Justin, up to which time he is stated to have remained quite orthodox.(2) The date may with much greater probability be set between a.d. 170—180.(3)
The earliest writer who mentions Tatian's Gospel is Eusebius,(4) who wrote some century and a half after its supposed composition, without, however, having himself seen the work at all, or being really acquainted with its nature and contents.(5) Eusebius says: "Tatian, however, their former chief, having put together a certain amalgamation and collection, I know not how, of the Gospels, named this the Diatessaron, which even now is current with some."(6)
It is clear that such hearsay information is not to be relied on.