What external evidence do we have for who wrote the Gospel of John?

Question

It seems the Gospel of John was written in the late 80s or early 90s. If John was around Jesus age when they both met, then he would have been 80 or 90 years when writing it.

In that time, people didn't usually live that long. The average was probably around 37 years the only 25% of the population would live 50 or 70 years (being generous)

I've seen some people say the Gospel of John was written probably by followers of John rather than by himself, but in this case... it doesn't sound like an inspired word from God but more like the remaining of John's word in his followers.

Note that there is already a question asking for the internal evidence of authorship, answers to this question should focus on the external evidence.

Answer 1

Christian tradition holds that John did live to be 80 or 90.

We know from Polycarp, that John was still active in Ephesus, and baptised him directly. Following Schaff:

It is safe, then, to say that the apostle John, with other disciples of Christ, came from Palestine to Asia Minor. If Polycarp, on the day of his death (Feb. 23, 155), was looking back on eighty-six years of life as a Christian, not as a man, and was thus baptized in 69, and if his conversion (according to Iren�us, Haer., III., iii. 4) was the work of an apostle, this migration to Asia Minor must have occurred before that date, possibly as a result of the outbreak of the Jewish war. John, then perhaps not more than sixty or sixty-five, would thus have been able to devote some thirty years to the fostering of Christian life in the province.]

Likewise, of Revelation, Schaff writes:

Space forbids going into the long history of the hypotheses which have been set forth as to the growth of the book, which is frequently held to have been a lengthy process. The following conclusions, however, seem safe. The assertion of Irenaeus (Haer., V., xxx, 3) that the visions were seen and the book written toward the end of the reign of Domitian, or about 95, finds support in the numerous historical data of the opening chapters. The designed and immediately accomplished introduction of the book into public liturgical use precludes the possibility of any notable alterations in it between 100 and 150. The author, as his name and idiom show, is of Hebrew birth, and about 95 had a recognized position of authority over the church of the province, without having any contemporary rival of the same name. He is the only John of Ephesus of whom anything is known from a tradition reaching back into his lifetime and in decisive points independent of his own writings. That he does not call himself an apostle is no proof that he was not one; his apostleship had no immediate connection with his apocalyptic purpose, and he does not describe himself at all

Put more simply, whoever wrote Revelation was the most important John out there, and that he was the same disciple makes sense.

He was, according to tradition both the youngest of the disciples and the one who lived the longest. Tradition also states that the older he grew, the shorter his sermons would be, until they could simply be "Little Children, Love one another!"

The average life expectancy is much lower, because so many people died as young infants or children - but once you made it to you teens, you could expect to live quite a while.

Answer 2

John, son of Zebedee

A good deal of modern theological analysis supports the presumption that John of Zebedee wrote this gospel. This is almost invariably speculative and tends to use circular reasoning: for example, proponents believe that the Gospel was written around 80-90 CE and also believe that John lived into his nineties at least, so he could have written the gospel that now bears his name. Or that we think the book was written in Ephesus and the apostle John is the only John of Ephesus of whom anything is known - thus jumping from a presumption that the book was written in Ephesus to a presumption that the author was called John and finally that he must have been the apostle John because a late tradition links John to Ephesus. None of this is external evidence in an objective sense.

Urban C. von Wahlde (The Gospel and Letters of John, Volume 3, page 412) says that Irenaeus was the first to mention the apostle John as the author of the Gospel, saying that his information came from Polycarp. von Wahlde sees more significance in the absence of early references to John as author than he sees in Irenaeus' report, since the accuracy of his report is in doubt on other grounds. In short, von Wahlde says there is no reliable evidence that John, son of Zebedee was the author of the Gospel.

John of Patmos

Now, we should also rule out the author of Revelation as the author of the John's Gospel. The author of Revelation actually identifies himself as a person called John, but the author of the fourth gospel chose to be anonymous. It would be flawed reasoning to say that because the Gospel was eventually attributed to the apostle John that any other important early Christian author named John must also be the apostle John. The theology and style of Revelation are far removed from the theology and style of John. Burton L. Mack says in Who Wrote the New Testament, page 197, that even after the Book of Revelation was blessed for posterity by inclusion in Athanasius' list of apostolic writings, there were doctors of the church who questioned its authenticity and groused about its theology. Wikipedia tells us that Dionysius of Alexandria noted that the gospel and the epistles attributed to John, unlike Revelation, do not name their author, and that the Greek of the gospel is correct and elegant while that of Revelation is neither. So, today, scholars tend to refer to the author of Revelation as 'John of Patmos' to distinguish him from either the apostle John or the author of John's Gospel.

John the 'elder'

It can be argued that the author of the Johannine epistles wrote, or at least contributed to John. Wikipedia points out the phraseology of the first letter of John is very similar to that of the fourth gospel and the two works use many of the same characteristic words and phrases, such as light, darkness, life, truth, a new commandment, to be of the truth, to do the truth and only begotten son. In both works, the same basic concepts are explored: the Word, the incarnation, the passing from death to life, the truth and lies. The two works also bear many stylistic affinities to one another. In the words of Amos Wilder, the works share "a combination of simplicity and elevation which differs from the flexible discourse of Paul and from the more concrete vocabulary and formal features of the Synoptic Gospels. The three Johannine epistles appear to be from the same author, who remains nameless but calls himself 'the elder' (or presbyter) - see 2 John 1; 3 John 1. This 'elder' certainly was not the apostle John or any other apostle, since it is inconceivable that an apostle would simply designate himself as the elder when writing to people who knew him to be far more than a presbyter.

In conclusion, we are on reasonably safe ground in saying that the author of the three Epistles of John wrote or, more likely, contributed to the authorship of John's Gospel. This author remains anonymous in the epistles, but styles himself as the elder, or the presbyter.