It has become popular conventional wisdom that Christianity didn't have a Bible until the fourth century. Prior to Emperor Constantine, so it is said, there was no "fixed" number of books in the New Testament. It was a fluid time of negotiation in which lots of books vied for inclusion in a collection of books considered to be "Holy Scripture," including some that were eventually left out (e.g., Gnostic gospels).
And then, as the legend goes, the powerful Constantine and his cronies tired of the chaos, authoritatively put their foot down, and selected the 27 books that would be the New Testament. Dan Brown's Da Vinci Code went so far as to suggest that this occurred at the Council of Nicaea in 325. Kurt Eichenwald, in his ridiculous hit piece on the Bible in last month's Newsweek, repeats the claim that Constantine "ultimately influenced" which books made it into the New Testament.
There are lots of problems with this mythical telling of church history, not the least of which is that the Council of Nicaea never even addressed the question of what books "belong" in the New Testament, much less dictated it. Oops.
There's an even stronger historical indicator, however, that by the time Constantine reigned the books of the New Testament were near universally understood.
In 331 Constantine wrote a letter to Eusebius of Caesarea asking him to prepare 50 Bibles for use in Rome's churches. Remember, books were not printed at this time; they were copied by hand. A commission for 50 volumes was an astonishingly large request and a massive undertaking.
If you look carefully, there is something very important missing in the letter.
It apparently never occurred to the Emperor to instruct Eusebius what books to include in the Bibles. And it never occurred to Eusebius to even ask. There is only one plausible interpretation of these deafening silences: the status of the Christian canon was implicitly understood. Can you imagine a world in which there is hot controversy over the number of books in the New Testament, receiving a request from the Emperor of the known world for copies of the Bible, and not clarifying what he wanted in them? Neither can I.
That's because there was no hot controversy. Whatever messy confusion had existed about the question had obviously been so settled in the public mind that Constantine didn't feel the need to specify, and Eusebius didn't feel the need to ask. Moreover, I would suggest that for that level of implicit understanding, the question must have been settled for a very long time. Remember, this is a request from the Emperor: sort of a maximal, life-or-death kind of situation (what if he left out Constantine's favorite book!?). I would personally interpret this to mean that the question of the canon cannot have been a live issue in Eusebius's living memory. Sure, he was aware of "disputed books," but if he had lived through a period of "hot debate" about it, there seems to me no question but that he would have done his due diligence and asked.
Thus, the great canon controversy, far from being authoritatively "settled" in the fourth century by Constantine, wasn't by then even controversial at all.