In a nutshell, I think that the best mythicist option starts with a revelation that the Christ (the messiah) has already come to earth, been executed, and been exalted into heaven, with salvific consequences. My contention has been that this first revelation need not have contained any specific details as to the exact time and place (though I do prefer to think of the time as having been recent, due to statements in Paul and other early writers); that those details were added later as revelation filled them in; and that originally it was taken on faith that the events happened, and they were explicitly said to be hidden in some way.
Andrew and Peter both appear to think that, if the venue for this salvific activity were the earth, it would come with more details (apparently right from the start) as to time and place. I do not share such expectations, and would like on this thread to offer an analogy.
The analogy will not be perfect, not least because it does not involve a figure in whom very many people would wish to invest faith. But it occurs to me that there is a figure whose arrival has been prophesied in the scriptures, but who has not yet acted out the things for which he is supposed to become famous, and whom some Christians believe is already alive and living among us: the Antichrist.
(Never mind that the term Antichrist in the Bible does not refer to any one single apocalyptic figure; many of the Christians who believe that this figure is soon to appear on the stage of world events either do not stress out over such details or are using the title as a convenient shorthand.)
Speculation that the Antichrist has already been born is not a strictly modern phenomenon. Sulpicius Severus reports the following concerning Martin, bishop of Tours, in Dialogue 2.14, translated by Alexander Robert (http://www.newadvent.org/fathers/35032.htm):
He told us, too, that there was no doubt but that Antichrist, having been conceived by an evil spirit, was already born, and had, by this time, reached the years of boyhood, while he would assume power as soon as he reached the proper age (non est dubium, quin antichristus malo spiritu conceptus iam natus esset, et iam in annis puerilibus constitutus, aetate legitima sumpturus imperium).
However, my own exposure to this notion comes from my childhood, most of which I spent in Christian circles of the kind likely to produce fans of Hal Lindsey and Dave Hunt, both of whom have ventured forth speculations in this area (http://www.worldwithoutend.info/bbc/boo ... christ.htm):
Hal Lindsey wrote in 1970 that he believed that the Antichrist was alive somewhere in the world. He repeated this belief in 1977 when he wrote that it was his "personal opinion" that "he's alive somewhere now. But he's not going to become this awesome figure that we nickname the Anti-Christ until Satan possesses him, and I don't believe that will occur until there is this 'mortal wound' from which he's raised up." In 1980 he restated this conviction by writing that "this man [Antichrist] is alive today—alive and waiting to come forth." ....
Not to be outdone, Dave Hunt voices a similar opinion: "Somewhere, at this very moment, on planet Earth, the antichrist is almost certainly alive—biding his time, awaiting his cue. Banal sensationalism? Far from it! That likelihood is based upon a sober evaluation of current events in relation to Bible prophecy. Already a mature man, he is probably active in politics, perhaps even an admired world leader whose name is almost daily on everyone's lips."
Not to be outdone, Dave Hunt voices a similar opinion: "Somewhere, at this very moment, on planet Earth, the antichrist is almost certainly alive—biding his time, awaiting his cue. Banal sensationalism? Far from it! That likelihood is based upon a sober evaluation of current events in relation to Bible prophecy. Already a mature man, he is probably active in politics, perhaps even an admired world leader whose name is almost daily on everyone's lips."
Notice the lack of specifics concerning where and when, except for the guess as to about how old this figure might be. Despite the confidence that the Antichrist has already been born, no details are forthcoming regarding where this birth might have taken place, or where he might be living right now.
Jerry Falwell has expressed a similar opinion, but he was willing to offer a current living area for the Antichrist, as well, not to mention even more specificity as to his current age (http://www.emmanuelenid.org/media-overv ... d858db65a1, PDF):
Jerry Falwell once made the announcement that he believed the Antichrist was alive, in his thirties, and was a man living in Europe.
Even these details are quite vague, of course. This is far, far from a biography.
All that is happening is that these Christian men are reading their Bibles and making educated guesses about the figure predicted therein, about how he is going to appear and usher in the great tribulation. I say educated because the interpretation of Bible prophesies, though often seeming virtually free of rules to outsiders, actually does come with certain guidelines and traditional procedures of which insiders instinctively are aware. I say guesses because even those guidelines and procedures have never guaranteed results with true predictive power.
For example, Lindsey probably derived his confidence that the Antichrist was already among us from his even greater confidence that all the Biblically predicted signs were pointing to the imminent apocalypse that he popularized in his book, The Late Great Planet Earth. Hunt was almost certainly shared the same motivation, and probably derived his description of the Antichrist as politically active from certain NT verses which imply that he is a leader. And Falwell probably felt empowered to guess that the Antichrist was living in Europe based on the common modern fundamentalist identification of the ten horns of Daniel 7.24 with a revived Roman empire embodied (somehow) by the European Union, whose number of member states is variously pressed into place as 10 (somehow: http://www.fulfilledprophecy.com/page/the-10-nations).
I was never a Catholic, but apparently fundamentalists are not the only ones speculating that the Antichrist has already been born: http://www.texemarrs.com/062000/walkus.htm. Cardinal Giacomo Biffi derives his picture of the living, breathing embodiment of evil both from scriptural precedents and, apparently, from his own personal list of modern vices fit for such a nasty figure: vegetarianism, environmentalism, pacifism, and animal rights.
In all of these cases, the details are sparse because the scriptures revealing them are not exhaustively clear. Yet the venue is clearly earth, and the belief in this figure is very real (even if the confidence that this figure has already been born is not 100%).
I suggest that this is similar (not identical) to what I am imagining for the earliest Christians. They came to believe that the Christ had already acted in history, though secretly; they imagined this based on scriptural passages about Wisdom personified, the death of the righteous man, the suffering servant, the promise of the messiah, and possibly the seventy weeks (interpreted differently than modern critical scholars interpret it, naturally). They did not immediately have all the details. Some tradents may have been bolder than others in interpreting such details into the biography (like Falwell guessing Europe where Lindsay and Hunt were not so specific). Of course, Christ is a figure deemed worthy of faith and worship, whereas the Antichrist is just the opposite, so the tradents will have felt differently about their speculations than the fundamentalists about theirs. But still, the main point is that the details are vague because the scriptures are vague; that is what can happen when you base your beliefs on the scriptures (at least until the creative juices really start to flow and the sheer momentum of finding more details takes over).
Hopefully this helps put what I am suggesting into some perspective.
Ben.