It's not so much as it proof as it is stating the obvious...
So, the obvious fact is, "if someting exists, it was created," right? With the caveat that things don't create themselves, of course.
How does that not suggest an infinite timeline to you? Each thing created by something that must have existed before it, which itself must have been created by a prior thing, and so on, "
all the way down," as they say.
Of course, I don't think your position
really requires an Ultimate Beginning. All it really needs is something on a sufficiently grander scale than the human universe going on, to put things in perspective.
With the M-theory bit, for example, it doesn't really matter that the 'branes - the larger universe - already existed; the point is "our universe" once didn't, and was created by their intersection.
Similarly, with the idea of creation by a sentient God
ex nihilo, the universe - the whole totallity - always existed, even it consisted of just God, but that doesn't really matter to us; the point is that "this universe," the particular set of conditions in which we are able to live and which encompasses what we can percieve, was created by a larger force.
And coming back to evidence, it certainly does appear that there was a Big Explosion, and explosions
are awfully suspicious, suggesting that there's a larger game afoot. If such an explosion did occur and is in fact all-encompassing (as it physically appears to us to be), then in all likelyhood nothing that happened before it would have a detectable effect afterwards, so in practice it does mark the beginning of "our universe." In this sense our world was indeed created by larger forces about which we know almost nothing. Whether or not the "whole universe" (which would include whatever caused the explosion) always existed or not is interesting to think about but not, I think, terribly relevant to this specific discussion.
*nod* Ulitmately, I agree with your thread title, using the definition of God as, basically, "whatever that larger pattern is, of which we and the world we know are a part and product." I just like dancing with the devil in the details sometimes.
