Here we have the fourth Gospel definitely assigned to its author, and finally established in its place amongst the canonical or authoritative books.

It is true that the account of the way in which the Gospel came to be composed is mixed up with legendary matter.

According to it the Gospel was written in obedience to a dream sent to Andrew the Apostle, after he and his fellow disciples and bishops had fasted for three days at the request of John.

In this dream it was revealed that John should write the narrative subject to the revision of the rest.

So the Gospel is the work of an eyewitness, and, though it and the other Gospels differ in the objects of their teaching, all are inspired by the same Spirit.
There may perhaps in this be some kernel of historical fact, as the sort of joint authorship or revision to which it points seems to find some support in the concluding verses of the Gospel ('we know that his witness is true').