In regard to this Dr.Lightfoot says [Endnote 325:1], that 'we should probably not be exaggerating if we placed one or both of the principal Egyptian versions, the Memphitic and the Thebaic, or at least parts of them, before the close of the second century.' In support of this statement he quotes Schwartz, the principal authority on the subject, 'who will not be suspected of any theological bias.' The historical notices on which the conclusion is founded are given in Scrivener's 'Introduction.' If we are to put a separate estimate upon these, it would be perhaps that the version was made in the second century somewhat more probably than not; it was certainly not made later than the first half of the third [Endnote 325:2].
Putting this version however on one side, the facts that have to be explained are these.

Towards the end of the second century we find the four Gospels in general circulation and invested with full canonical authority, in Gaul, at Rome, in the province of Africa, at Alexandria, and in Syria.

Now if we think merely of the time that would be taken in the transcription and dissemination of MSS., and of the struggle that works such as the Gospels would have to go through before they could obtain recognition, and still more an exclusive recognition, this alone would tend to overthrow any such theory as that one of the Gospels, the fourth, was not composed before 150 A.D., or indeed anywhere near that date.
But this is not by any means all.

It is merely the first step in a process that, quite independently of the other external evidence, thrusts the composition of the Gospels backwards and backwards to a date certainly as early as that which is claimed for them.
Let us define a little more closely the chronological bearings of the subject.

There is a decidedly preponderant probability that the Muratorian fragment was not written much later than 170 A.D.
Irenaeus, as we have seen, was writing in the decade 180-190 A.D.
But his evidence is surely valid for an earlier date than this.