I am an orthodox Christian, ask me a question!

[Eilonnwy]

No. Wrong way around. You are not supposed to believe the earliest Gospels were written down after 70 A.D. for any other reason than presupposing that for them to be earlier, they have to really "predict" the fall of Jerusalem, rather than it being a coincidence or reasonable anticipation - and, after that presupposition, if you then further presuppose that to have to be either impossible or supernatural, of course you will say they were written after 70 A.D. on the grounds of the philosophical presupposition that no such thing can happen, though it isn't even neccesary -to begin with- to admit to such a supposedly real prediction being necessary for an earlier date. All other facts indicate a much earlier date, and for that reason earlier documents like Q have been proposed.

Your reasoning is completely idiotic. Of course we have to believe it was written after the fall, because we have no reason to believe prophecy, specifically with the earliest gospel writer, exists. Prophecy in and of itself, does not stand up to the Scientific Method.

You try to say we're making faulty presuppositions when we're dealing with provable fact and you're making the biggest assumptions of all and so your reasoning is utter crap.