I do not know very much about science and maths, and it seems from previous discussions to do with quantam foam 
you do, so please, keep it as much to philosophy as we can.
But we all know that whilst maths and the cosmological argument may both be a priori, when I look at maths I can see every step, every logical regression from the answer to the question. I can see the set in stone rules, the basic fundamentals that make maths what maths is and make it possible. This almost makes it a posteriori, because my observation has proven it, the rules that I can see, and the workings of the sum, prove it to me.
However, I can accept that everything has a cause, and this regression will lead to the start of the universe, but not neccessarily the start of existence. How do we know nothing exists outside of this universe, totally out of human comprehension and space and time and the rules of this universe?
We don't, is the simple answer. But we do know that we don't know. And when humans don't know, they make up stuff, and when it comes to making stuff up about why we exist, its called a deity.
If one is to believe in heaven, and a creator who is outside of all space and time, by the same acceptance, one must accept that there could be something else out there. The cosmological argument simply convinces me that the universe is finite.
The gap in logic from this priori kicks in at the point where it is proven that the universe must have a cause independent of itself, but it is not proven that it is a God. There is a void in humanitys knowledge, and numinus, you seem smarter than to fill it with a God.
