Graetz alone goes as far back as to the time of Hadrian.

Hagenbach, Hasse, Tischendorf, and Friedlaender fix upon the middle, Mosheim, Gieseler, Baur, and Engelhardt upon the second half, of the second century; while the following writers assume either generally the reign of Marcus Aurelius, or specially with Dr.Keim one of the two great persecutions--Spencer, Tillemont, Neander, Tzschirner, Jachmann, Bindemann, Lommatzsch, Hase, Redepenning, Zeller.

The only two writers mentioned by Dr.
Keim as contending for a later date are Ueberweg and Volkmar, 'who strangely misunderstands both Origen and Baur' [Endnote 263:1].
Volkmar is followed by the author of 'Supernatural Religion.' At whatever date Celsus wrote, it appears to be sufficiently clear that he knew and used all the four canonical Gospels [Endnote 263:2].
3.
The last document that need be discussed by us at present is the remarkable fragment which, from its discoverer and from its contents, bears the name of the Canon of Muratori [Endnote 263:3].
Whatever was the original title and whatever may have been the extent of the work from which it is taken, the portion of it that has come down to us is by far the most important of all the direct evidence for the Canon both of the Gospels and of the New Testament in general with which we have yet had to deal.

It is indeed the first in which the conception of a Canon is quite unequivocally put forward.

We have for the first time a definite list of the books received by the Church and a distinct separation made between these and those that are rejected.
The fragment begins abruptly with the end of a sentence apparently relating to the composition of the Gospel according to St.Mark.
Then follows 'in the third place the Gospel according to St.
Luke,' of which some account is given.